Epidemiologic research in an integrated regional medical care system: the Marshfield Epidemiologic Study Area

Modeling longitudinal oral health status and pneumonia risk: secondary data analyses of an integrated dental-medical cohort

BACKGROUND

Mounting evidence indicates potential associations between poor oral health status (OHS) and increased pneumonia risk. Relative pneumonia risk was assessed in the context of longitudinally documented OHS.

METHODS

Electronic medical/dental patient data captured from 2007 through 2019 were retrieved from the integrated health records of Marshfield Clinic Health Systems. Participant eligibility initiated with an assessment of OHS, stratified into the best, moderate, or worst OHS groups, with the additional criterion of 'no pneumonia diagnosis in the past 90 days'. Pneumonia incidence was longitudinally monitored for up to 1 year from each qualifying dental visit. Models were assessed, with and without adjustment for prior pneumonia incidence, adjusted for smoking and subjected to confounding mitigation attributable to known pneumonia risk factors by applying propensity score analysis. Time-to-event analysis and proportional hazard modeling were applied to investigate relative pneumonia risk over time among the OHS groups.

RESULTS

Modeling identified associations between any incident pneumonia subtype and 'number of missing teeth' (p < 0.001) and 'clinically assessed periodontal status' (p < 0.01), which remained significant following adjustment for prior pneumonia incidence and smoking. The hazard ratio (HR) for 'any incident pneumonia' in the best OHS group for 'number of missing teeth' was 0.65, 95% confidence interval (CI) [0.54 - 0.79] (unadjusted) and 0.744, 95% CI [0.61 - 0.91] (adjusted). The HR for 'any incident pneumonia' in the best 'clinically assessed periodontal status' group was 0.72, 95% CI [0.58 - 0.90] (unadjusted) and 0.78, 95% CI [0.62 - 0.97] (adjusted).

CONCLUSION/CLINICAL RELEVANCE

Poor OHS increased pneumonia risk. Proactive attention of medical providers to patient OHS and health literacy surrounding oral-systemic disease association is vital, especially in high-risk populations.

Dairy Farm Work and Protection from Gastrointestinal Illness

Gastrointestinal (GI) disorders are a major public health burden in the United States. Due to close contact with animals, farmers may be a high risk subgroup for acute GI infections, though some studies suggest farm work is actually protective against GI illness. The purpose of this study was to examine associations between dairy farm work and GI symptoms over 3 years. A prospective, matched cohort study was used that included 70 adult dairy farm workers and 74 matched (age, gender, ZIP code) non-farm participants from central Wisconsin. The outcome was mean GI symptom scores for abdominal pain, diarrhea, constipation, dyspepsia, nausea, and reflux, per the 23-item Gastrointestinal Symptoms Severity Index (GISSI). After adjustment for potential confounding variables, linear regression results indicated dairy farm workers had significantly lower GISSI scores for abdominal pain (mean±SE = 4.3 ± 1.1 dairy vs. 7.6 ± 1.1 non-farm, p = .047), diarrhea (3.2 ± 1.0 dairy vs. 7.0 ± 1.0 non-farm, p = .010), constipation (2.0 ± 0.8 dairy vs. 6.6 ± 0.8 non-farm, p < .001), and dyspepsia (2.0 ± 0.6 dairy vs. 3.9 ± 0.5 non-farm, p = .026). Working on a dairy farm was associated with significantly less frequent and severe GI illness symptoms in adults. Future research should identify underlying causal pathways, including possible farm animal exposures, that influence beneficial gut microbiota that could inform therapeutic remedies to help prevent clinical GI disorders.

COVID-19 vaccine coverage disparities in rural and farm children

BACKGROUND

The risks of severe outcomes associated with SARS-CoV-2 (COVID-19) are elevated in unvaccinated individuals. It remains crucial to understand patterns of COVID-19 vaccination, particularly in younger and remote populations where coverage often lags. This study examined disparities in COVID-19 vaccine coverage in farm children and adolescents.

METHODS

A cross-sectional analysis was conducted in patients of the Marshfield Clinic Health System (MCHS) in Wisconsin. The sample included children/adolescents age 5-17 years who were eligible for COVID-19 vaccine initiation for ≥ 90 days (as of September 30, 2022), stratified by those who lived vs did not live on a farm. Outcomes included COVID-19 vaccine initiation, series completion, and booster receipt. Multivariable regression was used to examine associations between COVID-19 vaccination and farm, as well as rural and non-rural, residence.

RESULTS

There were 47,104 individuals (5% farm residents) in the sample. Overall, 33% of participants initiated and 31% completed the COVID-19 vaccine series. After adjustment, farm residence was associated with significantly lower odds of COVID-19 vaccine initiation (aOR [95% CI] = 0.68 [0.61, 0.75], p < 0.001), series completion (aOR = 0.67 [0.60, 0.75], p < 0.001), and booster receipt (aOR = 0.73 [0.61, 0.88], p = 0.001). Secondary analyses found COVID-19 vaccine coverage was lowest in young children who lived on dairy farms.

CONCLUSIONS

COVID-19 vaccine coverage is low in north-central Wisconsin children and adolescents. Those who live on farms have significantly lower likelihood of COVID-19 vaccine initiation, series completion, and booster receipt compared to non-farm counterparts. Farm families are an underserved group and require more effective public health interventions designed to prevent COVID-19.

Regional surveillance of medically-attended farm-related injuries in children and adolescents

Purpose

Due to numerous environmental hazards such as heavy machinery and large livestock, youth who live and work on farms are at high risk of injury, disability, and death. This study described a regional surveillance system for monitoring farm-related injuries in children and adolescents. As the risk of farm-related injuries are not exclusive to farm residents, trends in farm-related injuries over the previous 5 years were reported and compared between children/adolescents who did and did not live on farms in north-central Wisconsin.

Methods

A retrospective cohort of child and adolescent patients of the Marshfield Clinic Health System was assembled. Incident farm-related injuries, including from agricultural work or other activities in a farm environment, were extracted from medical records from 2017 through 2021. Generalized linear models were created to compare age- and sex-adjusted farm-related injury rates by year.

Results

There were 4,730 (5%) in-farm and 93,420 (95%) out-farm children and adolescents in the cohort. There were 65 incident farm-related injury cases in the in-farm group and 412 in the out-farm group. The annual incidence rate of farm-related injuries was higher in the in-farm group, but changes during the 5-year timeframe were not significant in either group. In the in-farm group, rates ranged from a high of 61.8 [95% confidence interval (CI): 38.3, 94.5] incident farm-related injuries per 10,000 children/adolescents in 2017 to a low of 28.2 (13.5, 51.9) injuries per 10,000 children/adolescents in 2018. In the out-farm group, rates ranged from 10.7 (8.3, 13.6) to 16.8 (13.7, 20.5) incident farm-related injuries per 10,000 children/adolescents per year between 2017 and 2021. The in-farm group had a higher proportion of injured males and heavy machinery injuries, while the out-farm group had more all-terrain vehicle injuries and pesticide poisonings.

Conclusion

Farm residency remains hazardous for children and adolescents, as injury rates were three times higher in the in-farm group and remained stable over 5 years. All-terrain vehicle injuries were high in both groups, and should be a priority in rural safety interventions. With additional adaptations to other states, this surveillance model could be scaled across other healthcare systems.

Burden of medically attended influenza infection and cases averted by vaccination - United States, 2016/17 through 2018/19 influenza seasons

BACKGROUND

Epidemics of seasonal influenza vary in intensity annually, and influenza vaccine effectiveness (VE) fluctuates based in part on antigenic match to circulating viruses. We estimated the incidence of influenza and influenza cases averted by vaccination in four ambulatory care sites in the United States, during seasons when overall influenza VE ranged from 29% to 40%.

METHODS

We conducted active surveillance for influenza at ambulatory care settings at four sites within the United States Influenza Vaccine Effectiveness Network. We extrapolated the total number of influenza cases in the source populations served by these organizations based on incidence of medically attended acute respiratory illness in the source population and influenza test results in those actively tested for influenza. We estimated the number of medically attended influenza cases averted based on incidence, vaccine coverage, and VE.

RESULTS

From 2016/17 through 2018/19, incidence of ambulatory visits for laboratory-confirmed influenza ranged from 31 to 51 per 1,000 population. Incidence was highest in children aged 9-17 years (range, 56 to 81 per 1,000) and lowest in adults aged 18-49 years (range, 23-32 per 1,000). Medically attended cases averted by vaccination ranged from a high of 46.6 (95 % CI, 12.1- 91.9) per 1,000 vaccinees in children aged 6 months to 8 years, to a low of 6.9 (95 % CI, -5.1- 27.3) per 1,000 vaccinees in adults aged ≥ 65 years.

DISCUSSION

Even in seasons with low vaccine effectiveness for a particular virus subtype, influenza vaccines can still lead to clinically meaningful reductions in ambulatory care visits for influenza.

Hydrochlorothiazide use, sun exposure, and risk of keratinocyte cancer

Background

Keratinocyte cancer (KC) rates are increasing in the U.S., particularly in older age groups. Use of hydrochlorothiazide (HCTZ), due to its photosensitizing properties, and high sun exposure are two known NMSC risk factors, but their synergistic effects are undetermined. The purpose of this study was to examine the development of NMSC between adults who did and did not use HCTZ, as well as those with high and low sun exposure.

Methods

A retrospective case–control sample was assembled from adult patients in north-central Wisconsin (USA). Duration of HCTZ use and occupational sun exposure were extracted from electronic health records, along with a linked survey of lifetime sun exposure.

Results

There were 333 cases and 666 controls in the analytical sample. A significant main effect was observed for HCTZ duration in the full sample. Under low sun exposure, the odds of NMSC was 14% greater for each additional year of HCTZ use (aOR = 1.14 [1.11, 1.18], p < 0.001). In a sensitivity analysis of participants age 70 years and over, there was a borderline significant (p = 0.086) HCTZ use by high sun exposure interaction, suggesting modestly increased HCTZ risk in older, high sun exposure adults.

Conclusions

Consistent with prior studies, longer duration of HCTZ use was a predictor of NMSC in north-central Wisconsin adults. NMSC may be accelerated in HCTZ users with outdoor lifestyles, but future studies should attempt to further disaggregate specific effects of sun exposure time, HCTZ duration, and age on NMSC development.

Respiratory health, allergies, and the farm environment: design, methods and enrollment in the observational Wisconsin Infant Study Cohort (WISC): a research proposal

Epidemiologic and cross-sectional studies suggest that early life farming and animal exposures are associated with major health benefits, influencing immune development and modifying the subsequent risk of allergic diseases, including asthma. The Wisconsin Infant Study Cohort (WISC) study was established in central Wisconsin to test the hypothesis that early life animal farm exposures are associated with distinct innate immune cell maturation trajectories, decreased allergen sensitization and reduced respiratory viral illness burden during the first 2 years of life. Beginning in 2013, a total of 240 families have been enrolled, 16,522 biospecimens have been collected, and 4098 questionnaires have been administered and entered into a secure database. Study endpoints include nasal respiratory virus identification and respiratory illness burden score, allergic sensitization, expression of allergic disease, and anti-viral immune response maturation and profiles. The WISC study prospective design, broad biospecimen collections, and unique US rural community will provide insights into the role of environmental exposures on early life immune maturation profiles associated with protection from allergic sensitization and significant respiratory viral disease burden. The WISC study findings will ultimately inform development of new strategies to promote resistance to severe respiratory viral illnesses and design primary prevention approaches for allergic diseases for all infants.

Socio-environmental risk factors for medically-attended agricultural injuries in Wisconsin dairy farmers

BACKGROUND

Accidents are common in the agricultural industry, particularly among dairy farmers. How said farmers get hurt is well established, but far less is known about how distal, socio-environmental factors influence injuries. This study examined associations between medically-attended agricultural injuries and: (1) personal sociodemographic characteristics, and (2) farm environment features and general safety practices.

METHODS

A cross-sectional survey was implemented with linked data from electronic health records on prior agricultural injuries that occurred between 01/01/2002-12/31/2015. The sample included adult dairy producers who resided in north-central Wisconsin (USA) and were medically-homed to the Marshfield Clinic Health System. Multiple logistic regression was used to analyze associations between socio-environmental characteristics and agricultural injuries.

RESULTS

There were 620 dairy farmers in the analytical sample, with 50 medically-attended agricultural injuries observed during the 14-year study time period (5.7 injuries per 1000 dairy farmers per year). In the multivariable model, the odds of agricultural injury were significantly greater among farmers who have private individually-purchased health insurance (OR=4.25; 95% CI: 1.31, 13.84), do not live at their dairy operation (OR=2.91; CI: 1.27, 6.67), and do not provide safety training to their workers (OR=4.27; CI: 1.00, 18.21).

CONCLUSIONS

Dairy farmers in this analysis who did not live at their dairy operation, did not provide safety training to all their workers, or had individually-purchased health insurance were more apt to get injured, but more research is needed to confirm these findings in prospectively designed studies. How these factors can be directly addressed or otherwise used to better focus farm injury prevention initiatives should also be explored.

Incidence of Primary Biliary Cholangitis in a Rural Midwestern Population

BACKGROUND

Primary biliary cholangitis (PBC) is a rare disease with incidence that varies with time and geography. Only two studies have assessed PBC incidence in the United States, with the most recent appearing over a decade ago. The objective of the present study was to assess PBC incidence in the United States in a more recent era.

METHODS

The incidence of PBC was assessed in a population-based cohort in rural, Midwestern Wisconsin over two decades spanning from June 1992 through June 2011. Cases were initially identified in the electronic medical record and then manually verified for inclusion according to the American Association for the Study of Liver Disease criteria for PBC. Additional data were abstracted for verified cases.

RESULTS

A total of 79 cases of PBC were identified over the 20-year period for an overall age- and sex-standardized incidence of 4.9 cases per 100,000 person-years. Incidence was higher in females, but changes over time were not significant. After a mean 7.3 years follow-up, all-cause mortality of those with PBC was 29%, and estimated 10-year survival was 76%.

CONCLUSIONS

The overall incidence of PBC in a Midwestern population of the United States has remained relatively stable over the last two decades. Patients have better prognosis, and the survival of PBC cases has improved.

Comparison of Generic-to-Brand Switchback Rates Between Generic and Authorized Generic Drugs

STUDY OBJECTIVE

Generic drugs contain identical active ingredients as their corresponding brand drugs and are pharmaceutically equivalent and bioequivalent, whereas authorized generic drugs (AGs) contain both identical active and inactive ingredients as their corresponding brand drugs but are marketed as generics. This study compares generic-to-brand switchback rates between generic and AGs.

DESIGN

Retrospective cohort study.

DATA SOURCE

Claims and electronic health record data from a regional U.S. health care system.

PATIENTS

The full cohort consisted of 5542 unique patients who received select branded drugs during the 6 months prior to their generic drug market availability (between 1999 and 2014) and then were switched to an AG or generic drug within 30 months of generic drug entry. For these patients, 5929 unique patient-drug combinations (867 with AGs and 5062 with generic drugs) were evaluated.

MEASUREMENTS AND MAIN RESULTS

Ten drugs with AGs and generics marketed between 1999 and 2014 were evaluated. The date of the first generic prescription was considered the index date for each drug, and it marked the beginning of follow-up to evaluate the occurrence of generic-to-brand switchback patterns over the subsequent 30 months. Switchback rates were compared between patients receiving AGs versus those receiving generics using multivariable Cox proportional hazards models, controlling for individual drug effects, age, sex, Charlson Comorbidity Score, pre-index drug use characteristics, and pre-index health care utilization. Among the 5542 unique patients who switched from brand to generic or brand to AG, 264 (4.8%) switched back to the brand drug. Overall switchback rates were similar for AGs compared with generics (hazard ratio [HR] 0.86, 95% confidence interval [CI] 0.65-1.15). The likelihood of switchback was higher for alendronate (HR 1.64, 95% CI 1.20-2.23) and simvastatin (HR 1.81, 95% CI 1.30-2.54) and lower for amlodipine (HR 0.27, 95% CI 0.17-0.42) compared with the other drugs evaluated.

CONCLUSION

Overall switchback rates were similar between AG and generic drug users, indirectly supporting similar efficacy and tolerability profiles for brand and generic drugs. Reasons for differences in switchback rates among specific products need to be explored further.

Adverse Childhood Experiences and Health in Adulthood in a Rural Population-Based Sample

BACKGROUND

Adverse childhood experiences (ACEs), including emotional abuse, substance abuse in the household, separation or divorce, physical abuse, violence between adults, mental illness in the household, sexual abuse, or incarceration of a household member, have the potential to profoundly impact health and well-being in adulthood. To assess whether previously reported relationships between ACEs and health outcomes withstand validation, we conducted a community-based ACE study with the unique capacity to link self-reported ACEs and other survey results to validated health data in an electronic medical record (EMR).

METHODS

Information regarding ACEs and health outcomes was captured from 2013-2014 via a telephone survey of residents of the predominantly rural northern and central regions of Wisconsin and electronic abstraction of EMR data. ACE score was calculated by counting each exposure as one point. We examined the relationship between ACE score, type, and self-reported and validated health outcomes.

RESULTS

A total of 800 participants completed the telephone survey. Overall, 62% reported at least one ACE and 15% reported experiencing four or more. All self-reported measures of poor health were associated with increased ACE score. EMR data were positively correlated with ACE score for increased body mass index and diagnoses of depression, anxiety, and asthma. In contrast, diagnoses of hypertension, hypercholesterolemia, myocardial infarction, and skin and other cancers were inversely related to ACE score. Emotional abuse was the most common ACE reported followed by substance abuse in the household. ACEs tended to cluster so that people who reported at least one ACE were likely to have experienced multiple ACEs. There was no clear correlation between abuse type (e.g., direct abuse vs. household dysfunction) and health outcomes.

CONCLUSIONS

In the first community-based study to link self-reported ACEs to comprehensive health measures documented in the medical record, we observed previously reported associations between childhood adversity and poor outcomes in adulthood, but also noted an inverse relationship between ACE score and certain medical diagnoses. Potential explanations for this finding warrant further investigation.

Epidemiology of systemic lupus erythematosus in rural Wisconsin

We investigated the epidemiology of systemic lupus erythematosus (SLE) in the Marshfield Epidemiologic Study Area (MESA), a defined rural region where nearly all residents obtain their health care from a large clinic system. Computerized medical records were searched to identify MESA residents diagnosed with SLE from 1991 through 2001. Medical records were manually reviewed for all selected patients to identify cases of SLE using the 1982 revised American College of Rheumatology criteria. Patients with 4 criteria were classified as definite SLE. Age- and gender- specific SLE incidence rates (1991-2001), the population prevalence rate of SLE on 31 December 2001 and survival rates were calculated. We identified 117 MESA residents with definite SLE. The average age-adjusted incidence of definite SLE was 5.1 per 100 000 per year (95% CI: 3.6, 6.6) and the age-adjusted population prevalence was 78.5 per 100 000 (95% CI: 59.0, 98.0). The mean age at diagnosis among the 44 incident cases was 51.7 years (range: 14-90 years). Positive anti-nuclear antibody (ANA), hematologic abnormalities, arthritis and renal disease were common at diagnosis. Five- and 10-year survival rates were 88% and 76%, respectively. Epidemiologic characteristics of SLE in this rural Caucasian population are generally similar to those reported by other US studies. One notable difference is a relatively high incidence of SLE in older adults.

Birth weight and systemic lupus erythematosus

The fetal environment may be a contributing factor in the etiology of some adult diseases. This study examined whether birth weight, birth length and gestational age are associated with the subsequent development of systemic lupus erythematosus (SLE). The Marshfield Clinic Lupus Registry was searched to identify patients who were born at Saint Joseph’s Hospital in Marshfield, Wisconsin, USA. Birth data on each case and five age-, sex-, and race-matched controls were recorded from medical and delivery room register records. Perinatal data were obtained for 23 cases and 115 controls. The unadjusted mean birth weight was similar for cases (3407 + 581 g) and controls (3422 + 514 g). Birth length was not different between groups. Birth weight adjusted for gestational age, analysed by conditional logistic regression, was not statistically significantly different between groups. We concluded that birth weight and length were similar among SLE cases and controls, suggesting that these perinatal characteristics are not associated with subsequent SLE.

Epidemiologic trends in medically-attended tree stand fall injuries among Wisconsin deer hunters

BACKGROUND

Tree stand falls are the most common injury to hunters in the USA, but there is limited research on the topic. This study examined the 5-year trends in incident tree stand fall injuries in rural north-central Wisconsin and described patient demographics and injury features.

METHODS

A retrospective analysis was conducted on five prior hunting seasons, 2009-2013. Cases were ascertained from electronic health records via natural language processing that identified patients from the Marshfield Epidemiologic Study Area who received medical attention for a tree stand fall. Annual incidence rates were calculated using the number of hunting license holders in the target population, per administrative data from the Wisconsin Department of Natural Resources.

RESULTS

There were 16,556-16,902 deer hunters in any given year, with 39 (92% male) confirmed medically-attended tree stand fall injuries in 2009-2013. Injuries mainly occurred in the lower extremities (n=23), and included two fatalities and one paralysis case. The risk of tree stand fall injuries went from 6.0 (95% CI: 3.2, 11.1) per 10,000 hunters in 2009 to 3.6 (95% CI: 1.6, 7.9) per 10,000 hunters in 2013, which was not a significant change over 5 years (p=0.79). Most falls occurred among archery hunters, in the evening and when descending from a tree stand. Cases were demographically similar to the general population of Wisconsin deer hunters.

CONCLUSIONS

The current seasonal incidence rate of tree stand fall injuries is relatively low in rural Wisconsin, but with limited signs of improvement. Continued efforts are needed to promote the long-term safety of the hunting public.

Validation of Health Event Capture in the Marshfield Epidemiologic Study Area

OBJECTIVE

In this study, health event capture is broadly defined as the degree to which a group of people use a particular provider network as their primary source of health care services. The Marshfield Epidemiologic Study Area (MESA) is a valuable resource for population-based health research, but the completeness of health event capture has not been validated in recent years. Our objective was to determine the current level of outpatient and inpatient health event capture by Marshfield Clinic (MC) facilities and affiliated hospitals for people living within MESA.

DESIGN

A stratified sample survey with strata defined by MESA region (Central or North) and age group (<18 years or ≥18 years).

SETTING

24 ZIP codes in central and northern Wisconsin, USA.

PARTICIPANTS

2,485 individuals participated of the 4,313 sampled cohort members residing in MESA Central (N=61,041) and MESA North (N=25,906) on February 22, 2011.

METHODS

A health care utilization survey was mailed to a random sample stratified by age group and MESA region. Telephone interviews were attempted for nonrespondents. The survey requested information on sources of outpatient care and overnight hospital admissions. Population proportions representing health event capture metrics and corresponding 95% confidence intervals (CI) were estimated with analytic weights applied to account for the survey design.

RESULTS

Among those with an outpatient visit during the past 24 months, the most recent visit of an estimated 93% (95% CI, 91% - 94%) was at a MC facility. The most recent admission of an estimated 93% (95% CI, 90% - 96%) of those hospitalized in the past 24 months was at a hospital affiliated with MC. The proportion admitted to MC affiliated hospitals was higher for residents of MESA Central (97%) compared to MESA North (83%).

CONCLUSION

A high proportion of outpatient visits and inpatient admissions in MESA Central and MESA North are accessible in the MC electronic health record. This pattern of high health event capture has been demonstrated since the inception of MESA in 1991. The results from this study validate and support the continued use of MESA for population-based epidemiologic and clinical research.

Aspirin overutilization for the primary prevention of cardiovascular disease

Background

Aspirin is commonly used for the primary prevention of cardiovascular disease (CVD) in the US. Previous research has observed significant levels of inappropriate aspirin use for primary CVD prevention in some European populations, but the degree to which aspirin is overutilized in the US remains unknown. This study examined the association between regular aspirin use and demographic/clinical factors in a population-based sample of adults without a clinical indication for aspirin for primary prevention.

Methods

A cross-sectional analysis was performed using 2010–2012 data from individuals aged 30–79 years in the Marshfield Epidemiologic Study Area (WI, USA). Regular aspirin users included those who took aspirin at least every other day.

Results

There were 16,922 individuals who were not clinically indicated for aspirin therapy for primary CVD prevention. Of these, 19% were regular aspirin users. In the final adjusted model, participants who were older, male, lived in northern Wisconsin, had more frequent medical visits, and had greater body mass index had significantly higher odds of regular aspirin use (P<0.001 for all). Race/ethnicity, health insurance, smoking, blood pressure, and lipid levels had negligible influence on aspirin use. A sensitivity analysis found a significant interaction between age and number of medical visits, indicating progressively more aspirin use in older age groups who visited their provider frequently.

Conclusion

There was evidence of aspirin overutilization in this US population without CVD. Older age and more frequent provider visits were the strongest predictors of inappropriate aspirin use. Obesity was the only significant clinical factor, suggesting misalignment between perceived aspirin benefits and cardiovascular risks in this subgroup of patients. Prospective studies that examine cardiac and bleeding events associated with regular aspirin use among obese samples (without CVD) are needed to refine clinical guidelines in this area.

Identifying opportunities to improve aspirin utilization for the primary prevention of cardiovascular disease in a regional health care system

OBJECTIVE

Aspirin is an important part of primary cardiovascular disease prevention, but little is known about aspirin use patterns in regional health care systems. This study used electronic health records from Marshfield Clinic to identify demographic, geographic, and clinical predictors of aspirin utilization in central Wisconsin adults without cardiovascular disease.

METHODS

A cross-sectional design was employed using 2010-2012 data from patients in the Marshfield Epidemiologic Study Area. Individuals who took aspirin-containing medication daily or every other day were considered regular aspirin users. There were a total of 6678 adults in the target region who were clinically indicated for aspirin therapy for primary cardiovascular disease prevention, per national guidelines.

RESULTS

Aspirin was generally underutilized in this population, with 35% of all clinically indicated adults taking it regularly. Adjusted models found that individuals who were younger, female, not covered by health insurance, did not visit a medical provider regularly, smokers, were not obese, or did not have diabetes were least likely to take aspirin. In addition, there was some local variation in that aspirin use was less common in northeastern communities within the regional service area.

CONCLUSION

Several aspirin use disparities were identified in central Wisconsin adults without cardiovascular disease, with particularly low utilization observed in those without diabetes and/or without regular physician contact. Methods of using electronic health records to conduct primary care surveillance as outlined here can be adopted by other large health care systems in the state to optimize future cardiovascular disease prevention initiatives.

Clinical and radiographic findings in adults with persistent hypophosphatasemia

A serum alkaline phosphatase value below the age-adjusted lower limits of normal (hypophosphatasemia) is uncommonly encountered in clinical practice. The electronic and paper medical records of 885,165 patients treated between 2002 and 2012 at a large, rural, multispecialty health clinic were interrogated to estimate the prevalence and characterize the clinical and radiographic findings of adults whose serum alkaline phosphatase was almost always low (persistent hypophosphatasemia). We hypothesized that some of these patients might harbor previously unrecognized hypophosphatasia, a rare, inherited condition of impaired mineralization of bones and teeth. Persistent hypophosphatasemia (serum alkaline phosphatase ≤ 30 IU/L) was found in 1 of 1544 adult patients. These adult patients had more crystalline arthritis, orthopedic surgery, chondrocalcinosis, calcific periarthritis, enthesopathy, and diffuse idiopathic skeletal hyperostosis than a general adult patient population. A gender effect was observed. The clinical and radiographic findings of adult patients with persistent hypophosphatasemia resemble those of the adult form of hypophosphatasia. Clinicians should take notice of persistent hypophosphatasemia, consider the diagnosis of hypophosphatasia, and be cautious when considering potent anti-remodeling therapy in these adults. This population warrants further evaluation.

A novel method for studying the temporal relationship between type 2 diabetes mellitus and cancer using the electronic medical record

Background

We developed an algorithm for the identification of patients with type 2 diabetes and ascertainment of the date of diabetes onset for examination of the temporal relationship between diabetes and cancer using data in the electronic medical record (EMR).

Methods

The Marshfield Clinic EMR was searched for patients who developed type 2 diabetes between January 1, 1995 and December 31, 2009 using a combination of diagnostic codes and laboratory data. Subjects without diabetes were also identified and matched to subjects with diabetes by age, gender, smoking history, residence, and date of diabetes onset/reference date.

Results

The final cohort consisted of 11,236 subjects with and 54,365 subjects without diabetes. Stringent requirements for laboratory values resulted in a decrease in the number of potential subjects by nearly 70%. Mean observation time in the EMR was similar for both groups with 13—14 years before and 5–7 years after the reference date. The two cohorts were largely similar except that BMI and frequency of healthcare encounters were greater in subjects with diabetes.

Conclusion

The cohort described here will be useful for the examination of the temporal relationship between diabetes and cancer and is unique in that it allows for determination of the date of diabetes onset with reasonable accuracy.

Development of reusable logic for determination of statin exposure-time from electronic health records

OBJECTIVE

We aim to quantify HMG-CoA reductase inhibitor (statin) prescriber-intended exposure-time using a generalizable algorithm that interrogates data stored in the electronic health record (EHR).

MATERIALS AND METHODS

This study was conducted using the Marshfield Clinic (MC) Personalized Medicine Research Project (PMRP) a central Wisconsin-based population and biobank with, on average, 30 years of electronic health data available in the independently-developed MC Cattails MD EHR. Individuals with evidence of statin exposure were identified from the electronic records, and manual chart abstraction of all mentions of prescribed statins was completed. We then performed electronic chart abstraction of prescriber-intended exposure time for statins, using previously identified logic to capture pill-splitting events, normalizing dosages to atorvastatin-equivalent dose. Four models using iterative training sets were tested to capture statin end-dates. Calculated cumulative provider-intended exposures were compared to manually abstracted gold-standard measures of ordered statin prescriptions, and aggregate model results (totals) for training and validation populations were compared. The most successful model was the one with the smallest discordance between modeled and manually abstracted Atorvastatin 10mg/year Equivalents (AEs).

RESULTS

Of the approximately 20,000 patients enrolled in the PMRP, 6243 were identified with statin exposure during the study period (1997-2011), 59.8% of whom had been prescribed multiple statins over an average of approximately 11 years. When the best-fit algorithm was implemented and validated by manual chart review for the statin-ordered population, it was found to capture 95.9% of the correlation between calculated and expected statin provider-intended exposure time for a random validation set, and the best-fit model was able to predict intended statin exposure to within a standard deviation of 2.6 AEs, with a standard error of +0.23 AEs.

CONCLUSION

We demonstrate that normalized provider-intended statin exposure time can be estimated using a combination of structured clinical data sources, including a medications ordering system and a clinical appointment coordination system, supplemented with text data from clinical notes.

Drinking water systems, hydrology, and childhood gastrointestinal illness in Central and Northern Wisconsin

OBJECTIVES

This study investigated if the type of drinking water source (treated municipal, untreated municipal, and private well water) modifies the effect of hydrology on childhood (aged < 5 years) gastrointestinal illness.

METHODS

We conducted a time series study to assess the relationship between hydrologic and weather conditions with childhood gastrointestinal illness from 1991 to 2010. The Central and Northern Wisconsin study area includes households using all 3 types of drinking water systems. Separate time series models were created for each system and half-year period (winter/spring, summer/fall).

RESULTS

More precipitation (summer/fall) systematically increased childhood gastrointestinal illness in municipalities accessing untreated water. The relative risk of contracting gastrointestinal illness was 1.4 in weeks with 3 centimeters of precipitation and 2.4 in very wet weeks with 12 centimeters of precipitation. By contrast, gastrointestinal illness in private well and treated municipal areas was not influenced by hydrologic conditions, although warmer winter temperatures slightly increased incidence.

CONCLUSIONS

Our study suggests that improved drinking water protection, treatment, and delivery infrastructure may improve public health by specifically identifying municipal water systems lacking water treatment that may transmit waterborne disease.

Inactivated influenza vaccines for prevention of community-acquired pneumonia: the limits of using nonspecific outcomes in vaccine effectiveness studies

BACKGROUND

One to 4 million cases of community-acquired pneumonia (CAP) occur annually in the United States, resulting in 600,000 hospitalizations and 45,000 deaths. Influenza infection facilitates secondary bacterial infections, and influenza vaccination may prevent CAP directly by preventing influenza pneumonia or indirectly by preventing secondary bacterial CAP.

METHODS

We investigated how influenza vaccination could affect incidence of CAP using deterministic probability and stochastic simulation models. The models included likely influential factors, including vaccine effectiveness (VE) against influenza, rates of influenza in the unvaccinated, vaccination coverage, and the relative risk (RR) of pneumonia, given influenza infection. To estimate effectiveness of influenza vaccine against CAP, we assumed mean VE against influenza of 55% and vaccine coverage of 38%.

RESULTS

Given our baseline parameters, influenza vaccine had a mean effectiveness against CAP of 7% (95% confidence interval = 0-25%). Effectiveness of influenza vaccine against CAP increased as its effectiveness against influenza increased, as RR of pneumonia after influenza infection increased, and as rates of influenza among unvaccinated persons increased.

CONCLUSIONS

No matter how effective vaccine may be in preventing influenza infection, it is only modestly effective at preventing CAP. Because of the large annual burden of CAP, a vaccine that is only moderately effective in preventing influenza infection has the potential to prevent a substantial number of CAP cases. This modeling approach may be useful for planning influenza vaccine-probe studies and evaluating the effectiveness of other interventions targeted against infections that manifest in nonspecific outcomes.

Prostate cancer risk in pre-diabetic men: a matched cohort study

BACKGROUND

Diagnosis and duration of type 2 diabetes mellitus (DM) appear to be associated with decreased prostate cancer risk. Limitations of previous studies include methods of subject selection and accurate definition of DM diagnosis. We examined the temporal relationship between DM and prostate cancer risk exploring the period of greatest risk starting from the prediabetic to the post-diabetic period using clinical and administrative data to accurately define the date of DM diagnosis.

METHODS

We identified 5,813 men who developed DM between January 1, 1995 and December 31, 2009 (reference date, date of DM onset or matched date for non-diabetic cohort) and 28,019 non-diabetic men matched by age, smoking history, residence, and reference date. Prostate cancer incidence before and after the reference date was assessed using Cox regression modeling adjusted for matching variables, body mass index, insurance status, and comorbidities. Primary outcomes included hazard ratio (HR) and number needed to be exposed to DM for one additional person to be harmed (NNEH) or benefit (NNEB) with respect to prostate cancer risk.

RESULTS

After full adjustment, the HR for prostate cancer before DM diagnosis was 0.96 (95% CI 0.85-1.08; P=0.4752), and the NNEB was 974 at DM diagnosis. After the reference date, the fully-adjusted HR for prostate cancer in diabetic men was 0.84 (95% CI 0.72-0.97, P=0.0167), and the NNEB 3 years after DM onset was 425. The NNEB continued to decrease over time, reaching 63 at 15 years after DM onset, suggesting an increasing protective effect of DM on prostate cancer risk over time. No significant difference between the diabetic and non-diabetic cohort was found prior to reference date.

CONCLUSION

Prostate cancer risk is not reduced in pre-diabetic men but decreases after DM diagnosis and the protective effect of DM onset on prostate cancer risk increases with DM duration.

Accuracy of ICD-9-CM codes in identifying infections of pneumonia and herpes simplex virus in administrative data

PURPOSE

Clinical epidemiology studies increasingly rely on electronic medical records data. The validity of International Classification of Disease, Ninth Revision, Clinical Modification (ICD-9-CM) diagnosis codes is crucial as they are often used to identify conditions of interest. We evaluated the use of archived ICD-9-CM codes to identify two representative infection-related conditions, pneumonia and herpes simplex virus (HSV), in a defined health system.

METHODS

Records were obtained for a sample of 175 and 179 patients with ICD-9-CM codes for pneumonia and HSV, respectively. An adjudicated case status was assigned for each subject.

RESULTS

The presence of a single ICD-9-CM code had a positive predictive value of 88% for pneumonia and 86% for HSV. False positives (noncases) accounted for less than 10% of records evaluated for each condition.

CONCLUSIONS

Our study demonstrates that ICD-9-CM codes for pneumonia and HSV were valid markers of a true history of these conditions, suggesting that ICD-9-CM codes can be used to successfully identify infection-related conditions in epidemiologic studies. However, validation studies for individual conditions may help identify condition-specific strategies to improve the performance of diagnostic codes.

Regional epidemiologic assessment of prevalent periodontitis using an electronic health record system

An oral health surveillance platform that queries a clinical/administrative data warehouse was applied to estimate regional prevalence of periodontitis. Cross-sectional analysis of electronic health record data collected between January 1, 2006, and December 31, 2010, was undertaken in a population sample residing in Ladysmith, Wisconsin. Eligibility criteria included: 1) residence in defined zip codes, 2) age 25–64 years, and 3) ≥1 Marshfield dental clinic comprehensive examination. Prevalence was established using 2 independent methods: 1) via an algorithm that considered clinical attachment loss and probe depth and 2) via standardized Current Dental Terminology (CDT) codes related to periodontal treatment. Prevalence estimates were age-standardized to 2000 US Census estimates. Inclusion criteria were met by 2,056 persons. On the basis of the American Academy of Periodontology/Centers for Disease Control and Prevention method, the age-standardized prevalence of moderate or severe periodontitis (combined) was 407 per 1,000 males and 308 per 1,000 females (348/1,000 males and 269/1,000 females using the CDT code method). Increased prevalence and severity of periodontitis was noted with increasing age. Local prevalence of periodontitis was consistent with national estimates. The need to address potential sample selection bias in future electronic health record–based periodontitis research was identified by this approach. Methods outlined herein may be applied to refine oral health surveillance systems, inform dental epidemiologic methods, and evaluate interventional outcomes.

Analysis of urological procedures in men who died from prostate cancer using a population-based approach

What's known on the subject? and What does the study add? Very few studies have examined end-of-life urological studies in men with prostate cancer. These studies reported fewer procedures in men who received primary therapy for prostate cancer. However, these studies were typically single institution or had a short follow-up period. The present study is the first population-based study examining end-of-life urological procedures and uses a geographic region encompassing 385 000 patients. Furthermore, this study incorporates both hospital- and office-based procedures. This approach has not been previously undertaken.

OBJECTIVE

To determine using a population-based approach whether men with end-stage prostate cancer who had definitive primary therapy might require fewer urological interventions. Repeated urological procedures can impact health-related quality of life in patients dying from prostate cancer.

PATIENTS AND METHODS

Using the Marshfield Epidemiological Study Area (MESA) database and tumour registry, we compared end-of-life interventions in men who died from prostate cancer between 1991 and 2009. Patient charts were queried for urological procedures using International Classification of Disease Modification, 9th edition (ICD9) codes for 3 years before death. Clinicopathological information was examined including whether the patient had a history of primary therapy (radiation or radical prostatectomy).

RESULTS

Among 280 patients dying from prostate cancer, 52 (19%) required 153 urological procedures during the last 3 years of life. The frequency of procedures increased closer to death. The most common procedures involved nephrostomy tube (56%), Foley catheter (24%) and transurethral resection of the prostate (10%). Clinicopathological features did not predict the need for an end-of-life urological procedure. There was no difference in the frequency of upper or lower tract procedures in surgery or radiation patients compared with patients without primary therapy (P = 0.556 and P = 0.508). Using a Kaplan-Meier analysis, there were no differences between groups in the proportion of patients not requiring a procedure (n = 280; P = 0.179).

CONCLUSIONS

This is the first population-based study to examine the frequency of urological procedures in patients with end-stage prostate cancer. A minority of patients (19%) required urological procedures during the final 3 years of life. A history of surgery or radiation did not influence the overall risk for urological intervention.

Influenza vaccine effectiveness in Wisconsin during the 2007-08 season: comparison of interim and final results

BACKGROUND

During the 2007-08 influenza season, we reported an interim vaccine effectiveness (VE) estimate of 44% for preventing medically attended influenza. In this analysis we report results for the entire season and compare them with the interim estimate.

METHODS

Patients with feverishness, chills, or cough <8 days duration were prospectively recruited over 10 weeks and tested for influenza by real-time reverse transcriptase PCR (rRT-PCR). Case-control analyses were performed using data from patients with rRT-PCR confirmed influenza (cases) and ill patients without influenza (test-negative controls). VE was estimated as 100×(1-adjusted odds ratio) in a logistic regression model adjusting for age, week, and high risk medical condition. A sample of influenza isolates was antigenically characterized.

RESULTS

Influenza was detected by rRT-PCR in 865 (44%) of 1972 patients; 73% were type A and 27% were type B. VE was 37% (95% CI, 22-49%) overall and 44% (95% CI, 27-58%) among participants tested 0-3 days after illness onset. VE was 39% (95% CI, 2-62%) in children 6-59 months old and 37% (95% CI, -2% to 61%) in adults ≥50 years old. VE was 41% (95% CI, 24-53%) for influenza A and 31% (95% CI, 3-51%) for influenza B. All 24 characterized influenza A viruses were antigenically matched to the H3N2 vaccine strain, although 14 viruses exhibited mild antigenic drift. There was a lineage mismatch with the vaccine strain for all 39 characterized influenza B viruses.

CONCLUSIONS

The 2007-08 influenza vaccine provided modest protection against medically attended influenza in this population. The interim estimate of VE after 17 days closely approximated the final season VE, supporting the potential use of interim VE estimates while influenza seasons are still in progress.

The utility of BMD Z-score diagnostic thresholds for secondary causes of osteoporosis

This very large dual X-ray absorptiometry (DXA) cohort confirmed a significant, inverse relationship between bone mineral density (BMD) Z-scores and the presence of secondary causes of osteoporosis but receiver operating characteristic (ROC) curves indicate that Z-score diagnostic thresholds (such as -2.0) discriminate poorly between the presence and absence of secondary causes of osteoporosis.

INTRODUCTION

BMD Z-score diagnostic thresholds have been proposed to detect secondary causes of osteoporosis. To determine the sensitivity and diagnostic utility of such thresholds, we analyzed comprehensive BMD and personal health information data from a large, multispecialty group practice.

METHODS

Adult subjects were assigned their lowest axial BMD Z-score and ICD-9 diagnosis codes for secondary causes of osteoporosis when cited at least twice in their electronic medical record. Multiple logistic regression was used to model the prevalence of matching ICD-9 codes as a function of Z-score. ROC curves were used to investigate various Z-score cut points for sensitivity and specificity.

RESULTS

Eighteen thousand six hundred seventy-four subjects were analyzed. Secondary causes of osteoporosis were identified in 31% of men and 16% of women. The frequency of secondary causes varied with age and between genders and varied inversely with Z-score. No inflection point was observed in this relationship to suggest a useful clinical decision threshold. The difference in mean Z-score of those with and without a secondary cause of osteoporosis was biologically slight (±0.3). Low Z-score diagnostic thresholds were insensitive to the presence of secondary causes of osteoporosis and provided relatively poor predictive value.

CONCLUSIONS

This DXA cohort confirmed a significant inverse relationship between Z-score and the presence of secondary causes of osteoporosis but diagnostic Z-score thresholds discriminate poorly between the presence and absence of secondary causes of osteoporosis. If only patients with very low Z-scores are evaluated for secondary causes of osteoporosis the diagnostic specificity may be high but most cases will be missed.

Urolithiasis in a rural Wisconsin population from 1992 to 2008: narrowing of the male-to-female ratio

PURPOSE

Urolithiasis is a common disease with multiple etiologies and risk factors. Studies suggest an increased incidence in developed nations in recent decades as well as differential geographic incidence and prevalence rates, and differences between the genders. We updated urolithiasis epidemiological data by examining the incidence and prevalence rates in a stable rural Wisconsin population.

MATERIALS AND METHODS

Data were obtained from the Marshfield Epidemiologic Study Area database, a surveillance tool created in 1991 to track disease in residents of an area of 24 ZIP Codes including approximately 85,000 individuals, of whom most receive care at Marshfield Clinic and affiliates. Urolithiasis cases were identified using ICD-9 codes. Incidence, prevalence and recurrence rates were determined.

RESULTS

The mean age adjusted incidence of new onset urolithiasis per 100,000 person-years was 202 (95% CL 168-235) in 1992 and 289 (95% CL 253-325) in 2008. In women the increase per 100,000 person-years was higher than in men, that is 171 (95% CL 129-213) and 289 (95% CL 238-340) vs 238 (95% CL 184-290) and 296 (95% CL 244-348), respectively. The male-to-female incidence ratio decreased from 1.4 to 1.0. The age adjusted prevalence per 100,000 individuals was 1,968 (2%) and 3,554 (3.5%) in 1992 and 2008, respectively. The increase in women was higher than in men (52% vs 26%). The age adjusted recurrence rate per 100,000 individuals was 553 (0.72%) and 676 (1.0%) in 1992 and 2008, respectively. The increase in women was higher than in men (88% vs 20%).

CONCLUSIONS

Since 1992, urolithiasis incidence, prevalence and recurrence rates in this rural Wisconsin population have increased with higher increases noted in women. While prevalence increased, it was lower than reported in other geographic areas in the United States.

Association of B-type natriuretic Peptide levels with estimated glomerular filtration rate and congestive heart failure

BACKGROUND

The causes of elevated B-Type natriuretic peptide (BNP) levels are multifactorial. Renal dysfunction has been shown to affect BNP levels in some studies and the diagnostic value of BNP levels in the presence of chronic kidney disease has been questioned. Prior studies have involved small patient populations with variable outcomes noted. This study evaluated the association of BNP levels with an estimated glomerular filtration rate (eGFR) and presence or absence of congestive heart failure (CHF).

METHODS

A retrospective, cross-sectional study in which medical records were electronically screened, identified patients with a BNP level and serum creatinine measurement on the same day between December 2002 and March 2006.

RESULTS

Of 1739 eligible patients, 537 were positive for CHF and 1202 were negative for CHF by our criteria. There was a clear trend for BNP to be higher with the advancement of CHF, as determined by New York Heart Association (NYHA) classification (P<0.001). Median BNP levels increased from 65 pg/mL in patients without CHF to 496 pg/mL in patients with NYHA class IV CHF (P <0.001), and there was a strong inverse association with eGFR (P <0.001).

CONCLUSION

BNP levels show a strong inverse association with eGFR in both CHF and non-CHF patients. Currently best practice at most institutions involves use of BNP cutoff diagnostic levels not adjusted for eGFR. The data presented underlines that eGFR is a significant confounder of BNP measurement especially when renal status is compromised and interpretation of clinical significance in the presence of elevated BNP measures should take renal status into consideration.

Atrial flutter versus atrial fibrillation in a general population: differences in comorbidities associated with their respective onset

OBJECTIVE

Determine and compare the prevalence of known risk factors for cardiovascular disease among unselected individuals presenting with their first ever episode of atrial flutter (AFL) and atrial fibrillation (AF).

STUDY DESIGN AND SETTING

We evaluated 11 pre-selected clinical variables including age, sex, smoking history and other potential cardiac risk factors. Using the resources of the Marshfield Epidemiologic Study Area, a population-based database, all newly diagnosed cases of either AFL or AF in the region during a 4-year period were identified.

RESULTS

Among the 472 incident cases, 76 (16.1%) had AFL and 396 (83.9%) had AF. Compared to those with AF, subjects with AFL were more likely to have had a history of chronic obstructive pulmonary disease (25% vs. 12%, P = 0.006), heart failure (28% vs. 17%, P = 0.05), and smoking (49% vs. 37%, P = 0.06). Hypertension, on the other hand, was more common among individuals with AF (63% vs. 47%, P = 0.01).

CONCLUSION

This study represents the first report to evaluate potential differences in the conditions associated with the development of AFL versus AF. Research into the mechanisms of atrial arrhythmogenesis may lead to improved preventive and therapeutic interventions.

Herpes zoster and exposure to the varicella zoster virus in an era of varicella vaccination

OBJECTIVES

We performed a case-control study to determine if participants with herpes zoster had fewer contacts with persons with varicella or zoster, and with young children, to explore the hypothesis that exposure to persons with varicella zoster virus (VZV) results in "immune boosting."

METHODS

Participants were patients of the multispecialty Marshfield Clinic in Wisconsin. We identified patients aged 40 to 79 years with a new diagnosis of zoster from August 2000 to July 2005. We frequency matched control participants to case participants for age. We confirmed diagnoses by chart review and assessed exposures by interview.

RESULTS

Interviews were completed by 633 of 902 eligible case participants (70.2%) and 655 of 1149 control participants (57.0%). The number of varicella contacts was not associated with zoster; there was no trend even at the highest exposure level (3 or more contacts). Similarly, there was no association with exposure to persons with zoster or to children, or with workplace exposures.

CONCLUSIONS

Although exposure to VZV in our study was relatively low, the absence of a relationship with zoster reflects the uncertain influence of varicella circulation on zoster epidemiology.

Farming-related caustic ingestion by a 2-year-old: innocent play with costly results

Young children continue to ingest caustic materials while playing in farm work areas. However, recent agricultural safety and health literature scarcely mentions caustic ingestion, and national incidence data specific to childhood caustic ingestion occurring on farms were not found. We present a case report of a 2-year-old child who, while playing with her brother, ingested dairy pipeline cleaner (an alkali). This case, although not unique, raises concerns about current prevention efforts related to the use and storage of chemicals on farms, long-term medical problems and associated costs, and the level of tolerance regarding the intermingling of innocent child play with adult work.

Evaluation of self-reported and registry-based influenza vaccination status in a Wisconsin cohort

We evaluated influenza vaccination status as determined by self-report and a regional, real-time immunization registry during two influenza seasons when subjects were enrolled in a study to estimate vaccine effectiveness. We enrolled 2907 patients during the two consecutive seasons. The sensitivity and specificity of self-reported influenza vaccination when compared to immunization registry records were 95% and 90%, respectively. The positive predictive value of self-reported vaccination was 89% and negative predictive value was 96%. In our study population, self-reported influenza vaccine status was a sensitive and fairly specific indicator of actual vaccine status. Misclassification was more common among young children.

Prevalence of asthma in a general population cohort of farm children: comparison of estimates based on parental report and medical record review

Methods of ascertaining and defining asthma in epidemiologic research vary, and the extent of agreement between such measures is not clearly understood. Within a broader investigation of early-life farm exposures and risk of childhood asthma and other atopic conditions, the authors sought to generate and compare population-based estimates of asthma prevalence among farm children using several definitions, based on both parental report and medical chart review. The Marshfield Epidemiologic Study Area (MESA) is a geographically defined, population-based cohort that receives nearly all health care from Marshfield Clinic and affiliated institutions. The region includes about 2200 farms, and over 9500 children aged 5 to 17 years who were born in the region served as the study population. A stratified random sample of 1000 overselecting for likely farm resident children was drawn. Parents of 553 children completed the survey and gave permission to review medical records. Informative records were available for 531 (96%). A weighted analysis provided estimates for the full study population. Asthma ascertainment included parental reports of past asthma diagnosis, history of wheezing, and asthma medication use, as well as documentation of asthma diagnoses and medication use in the medical chart. Prevalence of asthma among farm children using a broad composite definition was 24.8%. Prevalence based on parental reports of a specific asthma diagnosis was 11.2%, whereas medical chart documentation of a past asthma diagnosis was found for 10.1% of farm children. Seventy-one percent of parental reports were validated in the charts, and 80% of chart-confirmed diagnoses were reported by the parent. Basing asthma prevalence for farm children on a history of asthma medication use gave a higher estimate than did history of a diagnosis. Of farm children, 19.2% reported wheezing or respiratory whistling, with 8.1% occurring in the past year. Observational research on asthma can be substantially influenced by ascertainment methods and case definitions. Although prevalence estimates based on a past asthma diagnosis were quantitatively similar for parental reports and chart confirmation, agreement on specific cases between the two sources was less than expected. Care should be taken to clearly describe asthma case definitions when reporting results of observational asthma research.

Intraocular pressure response to medication in a clinical setting: the Marshfield Clinic Personalized Medicine Research Project

PURPOSE

To estimate glaucoma and ocular hypertension prevalence and to describe temporal trends in prescribing patterns and intraocular pressure (IOP) response to topical medications used in glaucoma and ocular hypertension.

MATERIALS AND METHODS

The medical records of adult subjects enrolled in the population-based Marshfield Clinic Personalized Medicine Research Project were searched to identify participants who had been diagnosed with ocular hypertension or glaucoma and prescribed agent(s) to lower IOP. All IOPs before and after prescription of the IOP agents were recorded.

RESULTS

As of December 31, 2005, 18,773 adults were enrolled in the Personalized Medicine Research Project, 57.1% were female, and their mean age was 50.3 years (range, 18 to 101 y). The overall rate of definite glaucoma in subjects aged 50 years and above was 2.1% (95% confidence interval=1.2, 2.4) and the rate of treated ocular hypertension was 1.4% (95% confidence interval=1.2, 1.7). Topical beta-blockers were the agents prescribed for the majority of subjects until the year 2000, when prostaglandins, first used in 1995, became the primary agent prescribed. In 2005, 75% of subjects used prostaglandin analogs and 46% used topical beta-blockers. The largest relative reduction in IOP in the first 3 months after prescription was observed for prostaglandin analogs (21.4% mean relative reduction), followed by beta-blockers (20.9% mean relative reduction). There has been a significant decrease over time in mean IOP before initiating medical therapy (linear regression beta coefficient=-0.30, P<0.0001, r=0.09).

CONCLUSIONS

In this clinic-based setting, we found that treatment of glaucoma has changed over the past 20 years, with ophthalmologists more likely to begin treatment at lower baseline levels of IOP, and prostaglandin analogs the most commonly prescribed and agent to lower IOP.

Applying case definition criteria to irritable bowel syndrome

OBJECTIVE

The quality of documentation of signs and symptoms and validation of the diagnosis of irritable bowel syndrome (IBS) according to case definition criteria of Manning, Rome I and Rome II in an office setting has not been previously described. We sought to identify and validate cases of IBS based on the Manning, Rome I and Rome II diagnostic criteria in a rural practice setting.

SETTING

Marshfield Epidemiologic Study Area (MESA) Central consisting of 14 ZIP codes in central Wisconsin, USA.

METHODS

A retrospective cohort study involved 890 patients with the diagnostic codes 564.1 for irritable bowel syndrome and 306.4 spastic colon-psychogenic who had presented to the practice from 1993-2003. Duration, frequency, concordance and intensity of symptoms based on case definitions of IBS were abstracted from the medical records.

RESULTS

During the study period, 890 incident cases of IBS were identified. Only 404 met one or more of the three diagnostic criteria, 340 (84%) met only the Manning criteria, 35 (10%) met only Manning and Rome I criteria, 4 (1%) met both Manning and Rome II criteria, and 25 (6%) met Manning and Rome I and Rome II criteria. Age adjusted incidence rates per 100,000 person-years for validated IBS cases during the observational period were 87 to 170 by Manning (lower confidence interval [CI]: 57-127, upper CI: 116-213), 8 to 34 (lower CI: 0-14, upper CI: 16-53) for Rome I and 3 to 16 (lower CI: 0-3, upper CI: 8-28) for Rome II. Comparison of Rome I and Rome II showed moderate concordance (kappa statistic = 0.51; 95% CI: 0.39-0.64).

CONCLUSIONS

Only a small percentage of IBS cases with assigned diagnostic codes met case definition criteria for IBS. There were low concordance rates among the three diagnostic criteria applied.

Barrett's esophagus: incidence and prevalence estimates in a rural Mid-Western population

BACKGROUND AND AIMS

Barrett's esophagus (BE) predisposes to adenocarcinoma of the esophagus and survival in esophageal adenocarcinoma is low. We studied patients diagnosed with BE in the Marshfield Epidemiologic Study Area (MESA). Our objectives were to estimate the prevalence of diagnosed BE, estimate the annual incidence of initial diagnosis of BE, and characterize the demographics of patients diagnosed with BE.

METHODS

We retrospectively reviewed medical records of patients diagnosed with BE until December 31, 2002. The esophagogastroduodenoscopy (EGD) reports were reviewed to establish the presence of columnar epithelium. All slides were retrieved and reviewed by a gastrointestinal pathologist to establish the presence of intestinal metaplasia and dysplasia. Chart abstraction was conducted using a standardized form.

RESULTS

BE was histologically confirmed in 216 patients. All were white, 165 (76%) were male, and 81% had a hiatal hernia. Median age at diagnosis was 65.5 yr (range 17-94). Long-segment BE (LSBE) was present in 112 (51.9%) patients. The prevalence of histologically confirmed BE in MESA was 261.8 (95% CI 222.5-301.1) per 100,000 people. The incidence of an initial diagnosis of BE between 1996 and 2002 was 32.7 per 100,000 person-years (95% CI 27.1-38.2) and did not change significantly over the study period despite an increase in EGD rates. At the initial diagnosis, 41.7% of the patients were on proton pump inhibitors. Dysplasia was present in 24.5% of patients.

CONCLUSION

The incidence of initial diagnosis of BE in a stable white population did not change significantly over a 7-yr period, despite an increase in EGD rates.

Performance of Binax NOW Flu A and B and direct fluorescent assay in comparison with a composite of viral culture or reverse transcription polymerase chain reaction for detection of influenza infection during the 2006 to 2007 season

The Binax NOW Flu A and Flu B (Binax NOW), direct fluorescent assay (DFA), and viral culture were evaluated and compared with a composite of viral culture or reverse transcription polymerase chain reaction (RT-PCR). Participants with medically attended acute respiratory illness were identified through active surveillance during the 2006 to 2007 season, and consenting individuals (n=932) were tested for influenza by culture and RT-PCR. Physicians ordered a rapid antigen test (Binax NOW [n=73] or DFA [n=70]) according to their clinical judgment. The Binax NOW detected 11 of 18 influenza infections (sensitivity, 61%; 95% confidence interval [CI], 36-83%), whereas DFA detected 17 of 21 influenza infections (sensitivity 81%, 95% CI, 58-95%). Compared with culture/RT-PCR, specificity of both Binax NOW and DFA was 100%. During the 2006 to 2007 influenza season, DFA and Binax NOW demonstrated high specificity but failed to identify a substantial proportion of influenza infections.

Prevalence and mortality of patients with myocardial infarction and reduced left ventricular ejection fraction in a defined community: Relation to the second multicenter automatic defibrillator implantation trial

OBJECTIVES

We compared characteristics and mortality of patients from a community population meeting enrollment criteria of the second Multicenter Automatic Defibrillator Implantation Trial (MADIT II) to those of the MADIT II subjects.

BACKGROUND

MADIT II showed that implantable cardioverter-defibrillators (ICDs) reduce mortality in patients with myocardial infarction (MI) and low left ventricular ejection fraction (LVEF) <or=30%.

METHODS

We used the resources of the Marshfield Epidemiologic Study Area (MESA), a well defined geographic region to identify MADIT II-type patients and determined outcomes during a 2-year follow-up period.

RESULTS

Of 1,126 patients who survived an MI, 114 (10.1%) had an LVEF <or=30%, 30 had exclusions leaving 84 patients meeting MADIT II-eligibility with a prevalence of 1.95/1,000. Applied to the US population, there would be about 360,000 MADIT II eligible individuals. MESA patients were older and more likely to be women than their MADIT II counterparts. The cumulative probability of death at 2 years in MESA patients (22.7%) was similar to the MADIT II control group (22%), whereas the sudden cardiac death (SCD) rate was lower in MESA (2.6%) than in MADIT II control patients (12%).

CONCLUSIONS

Differences in demographics, clinical characteristics and risk of SCD in community patients could alter the effectiveness and cost-effectiveness of ICD therapy from results reported in clinical trials. Further research is urgently needed to determine if the evidence-base used to formulate practice guidelines should be generalized to all individuals who meet eligibility criteria for ICD therapy.

Performance of Directigen flu A+B enzyme immunoassay and direct fluorescent assay for detection of influenza infection during the 2004-2005 season

Early diagnosis of influenza infection is needed to optimize the benefit of prescribing antiviral drugs. However, the accuracy of rapid tests is highly variable. This study evaluated the performance of Directigen flu A+B enzyme immunoassay (EIA) and direct fluorescent assay (DFA) during the 2004-2005 influenza season. Participants with medically attended acute respiratory illness were identified through an active surveillance. Consenting patients (n=818) were enrolled and cultured for influenza. Physicians ordered a rapid antigen test (EIA or DFA) according to their clinical judgment. Physicians ordered rapid tests with EIA (n=109), DFA (n=86), or both (n=9) in 204 patients with acute respiratory illness who were also cultured for influenza. The EIA detected 18 of 43 influenza infections (sensitivity, 42%; 95% confidence interval [CI], 28-57%), whereas DFA detected 26 of 38 influenza infections (sensitivity, 68%; 95% CI, 53-81%). Compared with culture, specificity of both EIA and DFA was 96%. During the 2004-2005 influenza season, both the EIA and DFA had low sensitivity and failed to detect influenza in many patients.

Healthy People 2010 disease prevalence in the Marshfield Clinic Personalized Medicine Research Project cohort: opportunities for public health genomic research

OBJECTIVES

The purpose of this study was to estimate the prevalence of Healthy People 2010 disease conditions in a large population-based cohort in central Wisconsin (WI, USA) and to consider how these conditions can be prioritized for research based on the use of healthcare services, the prevalence of various disease states and the resulting study power.

METHODS

Healthy People 2010 diagnoses were estimated for participants in the Personalized Medicine Research Project (PMRP), a large population-based biobank for residents aged 18 years and older living in central Wisconsin. By interrogating the electronic medical record, three parameters were calculated for each diagnosis: mean number of concomitant diagnoses, mean number of annual clinic visits before diagnosis and mean number of clinic visits after diagnosis.

RESULTS

A total of 18,239 adults enrolled in PMRP from September 2002 to May 2005 and were included in the study. They had a mean age of 49 years (standard deviation: 18.5), ranging from 18-98 years; 57% were female. At least one Healthy People 2010 disease was diagnosed in 86.4% of the participants; 13.6% had never been diagnosed with any of these conditions. The median number of diagnoses per subject was three (range: 1-15). The median number of annual visits after diagnosis was lowest for chronic obstructive pulmonary disease (9.1) and highest for sleep apnea (17.9). Subjects with a diabetic retinopathy diagnosis had the highest number of concomitant diagnoses (mean: 6.8).

DISCUSSION

All of the diseases within the Healthy People 2010 list are purported to have at least some genetic component, with the exception of injuries. The PMRP cohort is large enough that diseases of public health importance can be studied in the context of a variety of clinical and environmental covariates. This database is being developed as a national resource and is particularly useful where the estimated disease prevalence is 5% or greater. For less common diseases, additional cases can be recruited from throughout the Marshfield Clinic system of care, with population-based controls selected from the main PMRP study cohort.

Informed consent and subject motivation to participate in a large, population-based genomics study: the Marshfield Clinic Personalized Medicine Research Project

BACKGROUND

The objective of this study was to measure subject perspective and reaction to participation in the Personalized Medicine Research Project (PMRP) and to identify factors predicting understanding of the study elements.

METHOD

Self-administered questionnaires were mailed to 1,593 subjects (10% sample). The questionnaire had three sections: section A consisted of 21 factual questions; section B consisted of 14 questions to assess the level of understanding about the PMRP concepts, and section C asked about the purpose of the PMRP.

RESULTS

The mean age of the 924 survey respondents was 52 years (SD = 16.9), with a range of 18-95 years. The majority of participants were female (n = 561, 61%). The percent of total correct responses for section A was significantly higher for females compared with males (males: 58.4% and females: 60.4%, t test = -2.18, p = 0.03) and age was significantly inversely related to percent of correct responses (beta coefficient = -0.122, p < 0.001). More than one third of the participants indicated that the USD 20 greatly influenced their decision to participate in the project. In a multiple logistic regression model, people living outside of Marshfield were significantly more likely to indicate that the USD 20 greatly influenced their decision to participate (odds ratio = 1.40, 95% confidence limit = 1.06, 1.86) and age was inversely related to the monetary influence on decision to participate (odds ratio = 0.98, 95% confidence limit = 0.97, 0.98).

CONCLUSION

Future community consultation efforts should highlight areas of lower understanding. In addition, research coordinators may need to take more time informing males and older individuals about project details so that they are making truly informed decisions about study participation.

Acute health events in adult patients with genetic disorders: the Marshfield Epidemiologic Study Area

PURPOSE

We ascertained and reviewed acute health events occurring in 2003 among patients age 18 and greater with well-defined single gene, chromosomal, and selected multifactorial conditions within the Marshfield Epidemiologic Study Area.

METHODS

Of 47,077 adult Marshfield Epidemiologic Study Area Central cohort members, 1,831 (3.9%) had been given at least one of 71 ICD-9 codes appropriate for genetic diagnoses of interest. Physician review narrowed this to 591 (1.3%) validated patients for the study. Of the 591, 527 (89.2%) patients registered 6,849 visits, which were manually reviewed to delineate acute, relevant health events in the urgent care and primary care provider setting.

RESULTS

A total of 244 acute relevant health events among 126 patients corresponding to 58 different genetic conditions were observed. Acute relevant health events corresponded to 3.4% of the total health events in patients identified with genetic problems. Categories of genetic conditions with the highest frequencies of acute relevant health events included chromosomal and microdeletion syndromes (21.3%), hematologic disorders (11.5%), muscular dystrophies (8.6%), and connective tissue disorders (10.2%).

CONCLUSIONS

These data have multiple applications and implications in addressing the natural history, long-term medical needs and financial impact of adult patients with genetic conditions.

Psychosocial Work Characteristics Predict Cardiovascular Disease Risk Factors and Health Functioning in Rural Women: The Wisconsin Rural Women's Health Study

BACKGROUND

The aim of the present study is to investigate the association between psychosocial work characteristics and health functioning and cardiovascular disease risk factors among rural women of central Wisconsin and compare psychosocial work characteristics between farm and nonfarm women.

METHODS

Stratified sampling was used to select a random sample (n = 1500) of farm and nonfarm women aged 25 to 71 years from the Central Marshfield Epidemiologic Study Area. The baseline examination included measurements of blood pressure, height, weight, and fasting blood lipids, glucose, and insulin. Psychosocial job condition was measured with the Karasek Job Content Questionnaires (JCQ). Health functioning was assessed by the Short Form-36 Health Survey.

RESULTS

The analysis of JCQ showed that nonfarm residents were more likely to have jobs with high demand and high decision latitude compared to farm residents. Also, the farm residents (40.3%) were more likely to be occupied in passive jobs (jobs with low levels of demand and control) than the nonfarm residents (26.9%). Among farm residents, psychological job demand was associated with HDL level (beta = 0.17), triglycerides (beta = 0.0), their ratio (beta = 0.005), and blood insulin level (beta = 0.014), and among nonfarm residents, psychological job demand was associated with diastolic blood pressure (beta = 0.17) and total cholesterol level (beta = 0.002).

CONCLUSION

Our results showed that rural farm residents had a higher prevalence of CVD risk factors and were more likely to be occupied in jobs with low levels of demand and control. Job stress predicted more CVD risk factors among farm residents compared to nonfarm residents. Therefore, interventions reducing job strain among rural farm residents are timely and necessary.