Validity of hospital discharge International Classification of Diseases (ICD) codes for identifying patients with hyponatremia

Validation of ICD-10 codes used to identify the main reason for hospitalization due to hyponatremia in Sweden

PURPOSE

Hyponatremia is the most common electrolyte disorder, with potentially serious consequences. Studies validating hyponatremia used as a principal diagnosis are lacking. Studying principal diagnoses is important since it indicates the main reason for inpatient care. The aim of this study was to assess the validity of principal diagnoses of hyponatremia according to the International Classification of Diseases, tenth revision (ICD-10) in patients discharged from hospital.

METHODS

Three independent reviewers retrospectively analyzed medical records of 428 hospitalized patients, ≥18 years old, discharged with a principal diagnosis of either hyponatremia or syndrome of inappropriate anti-diuretic hormone secretion (SIADH) from three different hospitals during 2014-2017. The positive predictive value of hyponatremia as a principal diagnosis was calculated.

RESULTS

The median age of the studied population was 73 (IQR 64-81) years and 69% were women. The range of sodium levels was < 100 to 139 mmol/L. The mean sodium level was 119 mmol/L. Of the patients 27% were treated in an intensive care unit (ICU)/high dependency unit (HDU). Hyponatremia was deemed to be the principal cause of inpatient care in 411 out of 428 patients, corresponding to a positive predictive value for hyponatremia as a principal diagnosis of 96% (CI 95% 94-98).

CONCLUSIONS

The current study showed that 19 diagnoses out of 20 were correct implying a high validity. Thus, a principal diagnosis of hyponatremia, appears to be a useful measure in clinical and epidemiological studies aiming to target a clinically relevant consequence of hyponatremia in hospitalized patients.

Diagnostic validity and solute-corrected prevalence for hyponatremia and hypernatremia among 1 813 356 admissions

Background and hypothesis

We aimed to evaluate the diagnostic validity of the International Classification of Diseases, 10th Revision (ICD-10) codes for hyponatremia and hypernatremia, using a database containing laboratory data. We also aimed to clarify whether corrections for blood glucose, triglyceride, and total protein may affect the prevalence and the diagnostic validity.

Methods

We retrospectively identified admissions with laboratory values using a Japanese hospital-based database. We calculated the sensitivity, specificity, and positive/negative predictive values of recorded ICD-10-based diagnoses of hyponatremia (E87.1) and hypernatremia (E87.2), using serum sodium measurements during hospitalization (<135 and >145 mmol/l, respectively) as the reference standard. We also performed analyses with corrections of sodium concentrations for blood glucose, triglyceride, and total protein.

Results

We identified 1 813 356 hospitalizations, including 419 470 hyponatremic and 132 563 hypernatremic cases based on laboratory measurements, and 18 378 hyponatremic and 2950 hypernatremic cases based on ICD-10 codes. The sensitivity, specificity, positive predictive value, and negative predictive value of the ICD-10 codes were 4.1%, 99.9%, 92.5%, and 77.6%, respectively, for hyponatremia and 2.2%, >99.9%, 96.5%, and 92.8%, respectively, for hypernatremia. Corrections for blood glucose, triglyceride, and total protein did not largely alter diagnostic values, although prevalence changed especially after corrections for blood glucose and total protein.

Conclusions

The ICD-10 diagnostic codes showed low sensitivity, high specificity, and high positive predictive value for identifying hyponatremia and hypernatremia. Corrections for glucose or total protein did not affect diagnostic values but would be necessary for accurate prevalence calculation.

Establishment and representativeness of the Stockholm Sodium Cohort: A laboratorial and pharmacoepidemiologic database covering 1.6 million individuals in the Stockholm County

OBJECTIVE

Hyponatremia is associated with considerable morbidity and mortality, but causal links have been difficult to establish. Here, we describe the establishment and representativeness of the Stockholm Sodium Cohort (SSC), designed to study etiologies and outcomes of hyponatremia.

STUDY DESIGN AND SETTING

All residents of Stockholm County undertaking at least one serum sodium test between 2005-2018 were included in the SSC. Individual-level test results from over 100 laboratory parameters relevant to hyponatremia were collected and linked to data on demographics, socioeconomic status, healthcare contacts, diagnoses and dispensed prescription medications using national registers.

RESULTS

A total of 1,632,249 individuals, corresponding to 64% of the population of Stockholm County, were included in the SSC. Coverage increased with advancing age, ranging from 32% in children and adolescents (≤18 years) to 97% among the oldest (≥80 years). The coverage of SSC included the vast majority of patients in Stockholm County diagnosed with diabetes mellitus (93%), myocardial infarction (98%), ischemic stroke (97%), cancer (85%), pneumonias requiring inpatient care (95%) and deaths (88%).

CONCLUSION

SSC is the first cohort specifically designed to investigate sodium levels in a large, population-based setting. It includes a wide range of administrative health data and laboratory analyses. The coverage is high, particularly among elderly and individuals with comorbidities. Consequently, the cohort has a large potential for exploration of various aspects of hyponatremia.

Medical Treatment in Heart Failure with Reduced Ejection Fraction: A Proposed Algorithm Based on the Patient's Electrolytes and Congestion Status

In heart failure (HF) with reduced ejection fraction (HFrEF), four classes of drugs (β-blockers, angiotensin-converting enzyme inhibitors/angiotensin receptor neprilysin inhibitors, mineralocorticoid receptor antagonists, and the most recent Sodium-Glucose Co-Transporters 2 Inhibitors) have demonstrated positive results in randomized controlled trials (RCTs). Nevertheless, the latest RCTs are not proper for comparison since they were carried out at various times with dissimilar background therapies and the patients enrolled did not have the same characteristics. The difficulty of extrapolating from these trials and proposing a common framework appropriate for all cases is thus obvious. Despite the fact that these four agents are now the fundamental pillars of HFrEF treatment, the built-up algorithm of initiation and titration is a matter of debate. Electrolyte disturbances are common in HFrEF patients and can be attributed to several factors, such as the use of diuretics, renal impairment, and neurohormonal activation. We have identified several HFrEF phenotypes according to their sodium (Na+) and potassium (K+) status in a "real world" setting and suggest an algorithm on how to introduce the most appropriate drug and set up therapy based on the patients' electrolytes and the existence of congestion.

Osmotic Demyelination Syndrome in Patients Hospitalized with Hyponatremia

BACKGROUND: Osmotic demyelination syndrome (ODS) is a rare but potentially devastating neurologic complication of hyponatremia. The primary objective of this study was to identify the proportion of patients who developed ODS in a large, contemporary, multicenter cohort of patients admitted to the hospital with hyponatremia. METHODS: We conducted a multicenter cohort study of patients admitted with hyponatremia at five academic hospitals in Toronto, Ontario, Canada, between April 1, 2010, and December 31, 2020. All adult patients presenting with hyponatremia (serum sodium level 8 mmol/l in any 24-hour period). RESULTS: Our cohort included 22,858 hospitalizations with hyponatremia. Approximately 50% were women, the average age was 68 years, and mean initial serum sodium was 125 mmol/l (standard deviation, 4.6), including 11.9% with serum sodium from 110 to 119 mmol/l and 1.2% with serum sodium less than 110 mmol/l. Overall, rapid correction of serum sodium occurred in 3632 (17.7%) admissions. Twelve patients developed ODS (0.05%). Seven (58%) patients who developed ODS did not have rapid correction of serum sodium. CONCLUSIONS: In this large multicenter study of patients with hyponatremia, rapid correction of serum sodium was common (n=3632 [17.7%]), but ODS was rare (n=12 [0.05%]). Future studies with a higher number of patients with ODS are needed to better understand potential causal factors for ODS.

Osmotic Demyelination Syndrome in Hospitalized Patients With Cirrhosis: Analysis of the National Inpatient Sample (NIS)

GOAL

Characterize prevalence of osmotic demyelination syndrome (ODS) in hospitalized patients with cirrhosis.

BACKGROUND

ODS is a serious complication of rapid serum sodium correction. Patients with cirrhosis experience labile sodium levels related to portal hypertension and diuretic use, often with rapid correction-intentional or unintentional-during hospitalizations.

STUDY

We used validated International Classification of Diseases, Ninth Revision (ICD-9) codes to identify inpatients 18 years and older with cirrhosis from the 2009-2013 National Inpatient Sample, excluding those with liver transplantation during hospitalization. The primary outcome was ODS (ICD-9 341.8). Baveno IV defined decompensated cirrhosis (stages 3 and 4); Charlson Comorbidity Index identified severe comorbid illness (score >3). Logistic regression modeled factors associated with ODS.

RESULTS

Of 547,544 adult inpatients with cirrhosis, 94 (0.02%) had ODS. Inpatients with versus without ODS were younger (54 vs. 57 y, P=0.0001), and more likely to have alcohol-related cirrhosis (58% vs. 33%, P<0.0001). ODS did not associate with decompensated cirrhosis (33% vs. 37%, P=0.43), specific complications (ascites 33% vs. 33%, P=0.97; hepatic encephalopathy 24% vs. 17%, P=0.06), or severe comorbid illness (12% vs. 16%, P=0.24). In both univariable and multivariable analysis, age [adjusted odds ratio (ORadj): 0.97, 95% confidence interval (CI): 0.95-0.99], female gender (ORadj: 1.53, 95% CI: 1.01-2.30), Hispanic race (ORadj: 0.41, 95% CI: 0.19-0.89), alcohol-related cirrhosis (ORadj: 2.65, 95% CI: 1.71-4.09), and congestive heart failure (ORadj: 0.37, 95% CI: 0.15-0.95) significantly associated with ODS.

CONCLUSION

In hospitalized patients with cirrhosis, ODS is extremely rare, and associated with alcohol-related cirrhosis, younger age, and female gender. ODS is not associated with liver disease severity, specific complications including ascites, or comorbid disease.

A cross-sectional survey of knowledge pertaining to IV fluid therapy and hyponatraemia among nurses working at emergency departments in Denmark

INTRODUCTION

Inappropriate fluid therapy may induce or worsen existing hyponatraemia with potentially life-threatening consequences. Nurses have an important role in assisting physicians in IV fluid prescribing. However, research is lacking in Denmark about nurses' knowledge pertaining to IV fluid therapy and hyponatraemia.

METHODS

An explorative cross-sectional survey was performed among Danish emergency department nurses in Spring 2019. Knowledge about IV fluid therapy was assessed for three common clinical scenarios, and multiple-choice questions were used to measure knowledge about hyponatraemia.

RESULTS

112 nurses responded to all scenario questions corresponding to 6.2% (112/1815) of the total population of nurses working at emergency departments in Denmark. In two of the three scenarios, a minority of nurses (8-10%) inappropriately selected hypotonic fluids. Nearly one third (31%) selected a hypotonic fluid for a patient with meningitis, which is against guideline recommendations. The study revealed limited knowledge about severe symptoms of hyponatraemia, patients at high risk, and hyperglycaemia-induced hyponatraemia.

CONCLUSION

In accordance with guideline recommendation, the majority of nurses did not select hypotonic fluids in three clinical scenarios commonly encountered in the emergency department. However, when setting up an educational program, further awareness is needed regarding symptoms of hyponatraemia, high-risk patients, and hyperglycaemia-induced hyponatraemia.

Are Further Interventions Needed to Prevent and Manage Hospital-Acquired Hyponatraemia? A Nationwide Cross-Sectional Survey of IV Fluid Prescribing Practices

BACKGROUND

Hyponatraemia is associated with increased morbidity, increased mortality and is frequently hospital-acquired due to inappropriate administration of hypotonic fluids. Despite several attempts to minimise the risk, knowledge is lacking as to whether inappropriate prescribing practice continues to be a concern.

METHODS

A cross-sectional survey was performed in Danish emergency department physicians in spring 2019. Prescribing practices were assessed by means of four clinical scenarios commonly encountered in the emergency department. Thirteen multiple-choice questions were used to measure knowledge.

RESULTS

201 physicians responded corresponding to 55.4% of the total population of physicians working at emergency departments in Denmark. About a quarter reported that they would use hypotonic fluids in patients with increased intracranial pressure and 29.4% would use hypotonic maintenance fluids in children, both of which are against guideline recommendations. Also, 29.4% selected the correct fluid, a 3% hypertonic saline solution, for a patient with hyponatraemia and severe neurological symptoms, which is a medical emergency. Most physicians were unaware of the impact of hypotonic fluids on plasma sodium in acutely ill patients.

CONCLUSION

Inappropriate prescribing practices and limited knowledge of a large number of physicians calls for further interventions to minimise the risk of hospital-acquired hyponatraemia.

Desmopressin and the risk of hyponatremia: A population-based cohort study

BACKGROUND

Desmopressin was approved by the Food and Drug Administration (FDA) in 1978 for use in diabetes insipidus and bleeding disorders, but it is also prescribed off-label for patients with nocturia. Quantifying the potential risks facing adult patients taking desmopressin has taken on added importance because a new intranasal formulation of desmopressin was approved by the FDA in 2017. Like the old formulation, the main active ingredient is desmopressin acetate, but the new formulation also contains an excipient designed to enhance absorption. Our objective was to quantify the rate of hyponatremia in routine clinical care for patients prescribed the older formulation of desmopressin.

METHODS AND FINDINGS

We conducted a population-based new-user cohort study from 1 February 2006 to 1 February 2017 using a nationwide commercial health plan database. Patients newly prescribed the older formulation of desmopressin were propensity-score (PS)-matched to patients newly prescribed oxybutynin. As a sensitivity analysis, tamsulosin was used as the comparator rather than oxybutynin. The primary outcome was a primary position diagnosis of hyponatremia. Proportional hazard models after 1:1 PS matching were used to estimate hazard ratios (HRs) and 95% confidence intervals (CI). We identified 3,137 adults who were newly prescribed desmopressin and matched them to 3,137 adults who were newly prescribed oxybutynin. Mean age was 70, 55% were male, 13% filled a prescription for a diuretic during the baseline time period, and the mean baseline sodium prior to receiving either study drug was 140 mmol/L (normal: 135-145). The rate of hyponatremia was 146 per 1,000 person-years for adults prescribed desmopressin compared to 11 per 1,000 person-years for adults prescribed oxybutynin, corresponding to a 13-fold higher rate (HR 13.19; 95% CI 6.69, 26.01; p < 0.01). When follow-up was truncated at 30 days, a similar increased rate was observed (HR 19.41; 95% CI 7.11, 52.99; p < 0.01). A higher rate of hyponatremia was also observed with desmopressin when tamsulosin was the comparator (HR 12.10; 95% CI 6.54, 22.37; p < 0.01). Important limitations of our study include unmeasured confounding (for example, over-the-counter medication use, dietary intake), missing data (i.e., only 20% of patients had a baseline serum sodium), and a lack of data on the newer formulation of desmopressin.

CONCLUSIONS

Use of an older formulation of desmopressin was associated with a marked increased rate of subsequent hyponatremia compared to use of other medications indicated for lower urinary tract symptoms. Such risks should be clearly communicated to patients prescribed this formulation of desmopressin.

Prevalence of infant bronchiolitis-coded healthcare encounters attributable to RSV

AIM

We sought to determine the proportion of bronchiolitis episodes attributable to respiratory syncytial virus (RSV) among ICD-9 coded infant bronchiolitis episodes which were tested for RSV.

METHODS

Bronchiolitis healthcare encounters were extracted from Kaiser Permanente Northern California databases for years 2006 to 2009. We used ICD-9 codes for bronchiolitis to capture bronchiolitis-related healthcare encounters including hospital admissions (Hospitalization), emergency department visits (EDV), and outpatient visits (OPV). We reported the monthly proportion of RSV-positive bronchiolitis episodes among tested bronchiolitis episodes. We used logistic regression to assess association between bronchiolitis episodes and patient demographic and health care characteristics. We also used logistic regression to assess association between decision to test and patient demographics and health care characteristics.

RESULTS

Among 10,411 ICD-9 coded infant bronchiolitis episodes, 29% were RSV tested. Fifty one percent of those tested were RSV positive. Between December and February, and in infants ≤6 months, the proportion of bronchiolitis episodes that were attributable to RSV was 77.2% among hospitalized episodes, 78.3% among EDV episodes, and 60.9% among OPV episodes, respectively. The proportion of RSV-positive bronchiolitis episodes varied based upon infant age at diagnosis, level of health care service used, and time of the year of the episode.

CONCLUSION

Estimation of the proportion of ICD-9 coded bronchiolitis episodes attributable to RSV is more specific when restricting to bronchiolitis episodes during peak months, younger infant age, and those requiring higher level of healthcare.

Appropriateness of ICD-coded Diagnostic Inpatient Hospital Discharge Data for Medical Practice Assessment

Objectives: We performed a systematic review to investigate the quality of diagnostic hospital discharge data (DHDD) in order to gain insight in the usefulness of these data for medical practice assessment. We investigated the methods used to evaluate data quality, factors that determine data quality and its consequences for medical practice assessment.

Methods: We selected studies in which both completeness (or sensitivity: SENS) and correctness (or positive predictive value: PPV) were measured. We used the random-effects model to calculate mean SENS and PPV and to explore the effect of a number of covariates.

Results: The 101 included studies were very heterogeneous. We distinguished six typical study designs. We found a mean SENS of 0.67 (95%CI: 0.62– 0.73) and PPV of 0.76 (95%CI: 0.73– 0.79); SENS was significantly lower for comorbidity and complication studies than for some single disease studies. PPV was significantly higher for Scandinavian countries than for other countries. Recoding compared to re-abstracting of the medical record as a gold standard gave a significantly lower PPV. Diagnostic data were considered appropriate by the authors of the studies for quality of care purposes when both SENS and PPV were at least 0.85. Only 13% of the studies fulfilled this criterion.

Conclusions: Variability in quality of care between settings can easily be overshadowed by variability in data quality. However, the use of DHDD by physicians to evaluate their own medical practice may be useful. But only if physicians are willing to critically interpret the meaning of the information for their medical practice assessment.

Differences in Associations of Antidepressants and Hospitalization Due to Hyponatremia

BACKGROUND

Selective serotonin reuptake inhibitors (SSRIs) and other antidepressants are important as a cause of hyponatremia. However, most studies have focused on the effect on sodium levels regardless of clinical symptoms, or have been too small to be able to discriminate between the effects of specific antidepressant drugs. The objective of the present study was to investigate the association between different groups of antidepressants and the risk of hospitalization due to hyponatremia.

METHODS

In this register-based case-control study of patients in the general Swedish population, we identified 14,359 individuals with a main diagnosis of hyponatremia. For every case, 4 matched controls were included (n = 57,382). To investigate the temporal aspects of drug-induced hyponatremia, antidepressant exposure was divided into patients with newly initiated and ongoing treatment. Univariable and multivariable logistic regression was used to analyze the association of antidepressant use and hospitalization.

RESULTS

For newly initiated antidepressants, adjusted odds ratios (95% confidence interval) for a main diagnosis of hyponatremia compared with controls were: citalopram 5.50 (4.71-6.44); sertraline 4.96 (3.81-6.48); venlafaxine 5.28 (3.20-8.83); tricyclic antidepressants 1.59 (1.13-2.24); and mirtazapine 2.54 (2.04-3.16). Adjusted odds ratio (confidence interval) for individuals with ongoing treatment ranged from 0.57 (0.52-0.63) for citalopram to 1.08 (0.85-1.36) for other SSRIs.

CONCLUSIONS

There was a strong association between newly initiated treatment with SSRIs or venlafaxine and hospitalization due to hyponatremia. The association for tricyclic antidepressants and mirtazapine was small to moderate. In contrast, there was no evidence that ongoing treatment with antidepressants increases the risk for hospitalization due to hyponatremia.

Hyponatremia in Guillain-Barré Syndrome

OBJECTIVES

To evaluate incidence, risk factors, and in-hospital outcomes associated with hyponatremia in patients hospitalized for Guillain-Barré Syndrome (GBS).

METHODS

We identified adult patients with GBS in the Nationwide Inpatient Sample (2002-2011). Univariate and multivariable analyses were used.

RESULTS

Among 54,778 patients hospitalized for GBS, the incidence of hyponatremia was 11.8% (compared with 4.0% in non-GBS patients) and increased from 6.9% in 2002 to 13.5% in 2011 (P < 0.0001). Risk factors associated with hyponatremia in multivariable analysis included advanced age, deficiency anemia, alcohol abuse, hypertension, and intravenous immunoglobulin (all P < 0.0001). Hyponatremia was associated with prolonged length of stay (16.07 vs. 10.41, days), increased costs (54,001 vs. 34,125, $USD), and mortality (20.5% vs. 11.6%) (all P < 0.0001). In multivariable analysis, hyponatremia was independently associated with adverse discharge disposition (odds ratio: 2.07, 95% confidence interval, 1.91-2.25, P < 0.0001).

CONCLUSIONS

Hyponatremia is prevalent in GBS and is detrimental to patient-centered outcomes and health care costs. Sodium levels should be carefully monitored in high-risk patients.

The Economic Burden of Hyponatremia: Systematic Review and Meta-Analysis

BACKGROUND

Hyponatremia is the most common electrolyte abnormality observed in clinical practice. Several studies have demonstrated that hyponatremia is associated with an increased length of hospital stay and of hospital resource utilization. To clarify the impact of hyponatremia on the length of hospitalization and costs, we performed a meta-analysis based on published studies that compared hospital length of stay and cost between patients with and without hyponatremia.

METHODS

An extensive Medline, Embase, and Cochrane search was performed to retrieve all studies published up to April 1, 2015 using the following words: "hyponatremia" or "hyponatraemia" AND "hospitalization" or "hospitalisation." A meta-analysis was performed including all studies comparing duration of hospitalization and hospital readmission rate in subjects with and without hyponatremia.

RESULTS

Of 444 retrieved articles, 46 studies satisfied the inclusion criteria, encompassing a total of 3,940,042 patients; among these, 757,763 (19.2%) were hyponatremic. Across all studies, hyponatremia was associated with a significantly longer duration of hospitalization (3.30 [2.90-3.71; 95% CIs] mean days; P < .000). Similar results were obtained when patients with associated morbidities were analyzed separately. Furthermore, hyponatremic patients had a higher risk of readmission after the first hospitalization (odds ratio 1.32 [1.18-1.48; 95% CIs]; P < .000). A meta-regression analysis showed that the hyponatremia-related length of hospital stay was higher in males (Slope = 0.09 [0.05-0.12; 95% CIs]; P = .000 and Intercept = -1.36 [-3.03-0.32; 95% CIs]; P = .11) and in elderly patients (Slope = 0.002 [0.001-0.003; 95% CIs]; P < .000 and Intercept = 0.89 [0.83-0.97; 95% CIs]; P < .001). A negative association between serum [Na(+)] cutoff and duration of hospitalization was detected. No association between duration of hospitalization, serum [Na(+)], and associated morbidities was observed. Finally, when only US studies (n = 8) were considered, hyponatremia was associated with up to around $3000 higher hospital costs/patient when compared with the cost of normonatremic subjects.

CONCLUSIONS

This meta-analysis confirms that hyponatremia is associated with a prolonged hospital length of stay and higher risk of readmission. These observations suggest that hyponatremia may represent one important determinant of the hospitalization costs.

Predictive Validity of the Beers and Screening Tool of Older Persons' Potentially Inappropriate Prescriptions (STOPP) Criteria to Detect Adverse Drug Events, Hospitalizations, and Emergency Department Visits in the United States

OBJECTIVES

To compare the predictive validity of the 2003 Beers, 2012 American Geriatrics Society (AGS) Beers, and Screening Tool of Older Persons' potentially inappropriate Prescriptions (STOPP) criteria.

DESIGN

Retrospective cohort.

SETTING

Managed care administrative claims data from 2006 to 2009.

PARTICIPANTS

Commercially insured persons aged 65 and older in the United States (N=174,275).

MEASUREMENTS

Association between adverse drug events (ADEs), emergency department (ED) visits, and hospitalization outcomes and inappropriate medication use using time-varying Cox proportional hazard models. Measures of model discrimination (c-index) and hazard ratios (HRs) were calculated to compare unadjusted and adjusted models for associations.

RESULTS

The prevalence of inappropriate prescribing was 34.1% for the 2012 AGS Beers criteria, 32.2% for the 2003 Beers criteria, and 27.6% for the STOPP criteria. Each set of criteria modestly discriminated ADEs in unadjusted analyses (STOPP criteria: hazard ratio (HR)=2.89, 95% confidence interval (CI)=2.68-3.12, C-index=0.607; 2012 AGS Beers criteria: HR=2.51, 95% CI=2.33-2.70, C-index=0.603; 2003 Beers criteria: HR=2.65, 95% CI=2.46-2.85, C-index=0.605). Similar results were observed for ED visits and hospitalizations. The c-indices increased to between 0.65 and 0.70 in adjusted analyses. The kappa for agreement between criteria was 0.80 for the 2003 and 2012 AGS Beers criteria, 0.58 for the 2012 AGS Beers and STOPP criteria, and 0.59 for the 2003 Beers and STOPP criteria. For the three outcomes, the 2012 AGS Beers criteria had the highest sensitivity (61.2-71.2%) and the lowest specificity (41.2-70.7%), and the STOPP criteria had the lowest sensitivity (53.8-64.7%) but the highest specificity (47.8-78.1%).

CONCLUSION

All three criteria were modestly prognostic for ADEs, EDs, and hospitalizations, with the STOPP criteria slightly outperforming both Beers criteria. With low sensitivity, low specificity, and low agreement between the criteria, they can be used in a complementary fashion to enhance sensitivity in detecting ADEs.

The Impact of the Choice of Data Source in Record Linkage Studies Estimating Mortality in Venous Thromboembolism

Linked electronic healthcare databases are increasingly being used in observational research. The objective of this study was to investigate the impact of the choice of data source in estimating mortality following VTE, with a secondary aim to investigate the influence of the denominator definition. We used the UK Clinical Practice Research Datalink (CPRD) to identify patients aged 18+ with venous thromboembolism (VTE). Multiple cohorts were identified in order to assess how mortality rates differed with a range of data sources. For each of the cohorts, incidence rates per 1,000 person years (/1000py) and relative rates (RRs) of all-cause mortality were calculated. The lowest mortality rate was found when only primary care data were used for both the exposure (VTE) and the outcome (death) (108.4/1000py). The highest mortality rate was found for patients diagnosed in secondary care (237.2/1000py). When linked primary and secondary care data were included for eligible patients and for the overlapping period of data collection, a mortality rate of 173.2/1000py was found. Sensitivity analyses varying the denominator definition provided a range of results (140.6–164.3/1000py). The relative rates of mortality by gender and age were comparable across all cohorts. Depending on the choice of data source, the population studied may be different. This may have substantial impact on the main findings, in particular on incidence rates of mortality following VTE.

Dietary Salt Restriction in Heart Failure: Where Is the Evidence?

Several dietary guidelines, health organizations and government policies recommend population-wide sodium restriction to prevent hypertension and related comorbidities like heart failure (HF). The current European Society of Cardiology and American College of Cardiology/American Heart Association Heart Failure guidelines recommend restricting sodium in HF patients. However, these recommendations are based on expert opinion (level C), leading to wide variability in application and lack of consensus among providers pertaining to dietary salt restriction. To evaluate the strength of current evidences to recommend dietary salt restriction among HF patients, we performed a comprehensive literature review and explored the safety and efficacy of such recommendations.

Dehydration in the Elderly: A Review Focused on Economic Burden

BACKGROUND

Dehydration is the most common fluid and electrolyte problem among elderly patients. It is reported to be widely prevalent and costly to individuals and to the health care system. The purpose of this review is to summarize the literature on the economic burden of dehydration in the elderly.

METHOD

A comprehensive search of several databases from database inception to November 2013, only in English language, was conducted. The databases included Pubmed and ISI Web of Science. The search terms «dehydration» / "hyponaremia" / "hypernatremia" AND «cost» AND «elderly» were used to search for comparative studies of the economic burden of dehydration. A total of 15 papers were identified.

RESULTS

Dehydration in the elderly is an independent factor of higher health care expenditures. It is directly associated with an increase in hospital mortality, as well as with an increase in the utilization of ICU, short and long term care facilities, readmission rates and hospital resources, especially among those with moderate to severe hyponatremia.

CONCLUSIONS

Dehydration represents a potential target for intervention to reduce healthcare expenditures and improve patients' quality of life.

Validity of the International Classification of Diseases, 10th revision discharge diagnosis codes for hyponatraemia in the Danish National Registry of Patients

OBJECTIVE

To examine the validity of the International Classification of Diseases, 10th revision (ICD-10) codes for hyponatraemia in the nationwide population-based Danish National Registry of Patients (DNRP) among inpatients of all ages.

DESIGN

Population-based validation study.

SETTING

All somatic hospitals in the North and Central Denmark Regions from 2006 through 2011.

PARTICIPANTS

Patients of all ages admitted to hospital (n=819 701 individual patients) during the study period. The patient could be included in the study more than once, and our study did not restrict to patients with serum sodium measurements (total of n=2 186 642 hospitalisations).

MAIN OUTCOME MEASURE

We validated ICD-10 discharge diagnoses of hyponatraemia recorded in the DNRP, using serum sodium measurements obtained from the laboratory information systems (LABKA) research database as the gold standard. One sodium value <135 mmol/L measured at any time during hospitalisation confirmed the diagnosis. We estimated sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) for ICD-10 codes for hyponatraemia overall and for cut-off points for increasing hyponatraemia severity.

RESULT

An ICD-10 code for hyponatraemia was recorded in the DNRP in 5850 of the 2 186 642 hospitalisations identified. According to laboratory measurements, however, hyponatraemia was present in 306 418 (14%) hospitalisations. Sensitivity of hyponatraemia diagnoses was 1.8% (95% CI 1.7% to 1.8%). For sodium values <115 mmol/L, sensitivity was 34.3% (95% CI 32.6% to 35.9%). The overall PPV was 92.5% (95% CI 91.8% to 93.1%) and decreased with increasing hyponatraemia severity. Specificity and NPV were high for all cut-off points (≥99.8% and ≥86.2%, respectively). Patients with hyponatraemia without a corresponding ICD-10 discharge diagnosis were younger and had higher Charlson Comorbidity Index scores than patients with hyponatraemia with a hyponatraemia code in the DNRP.

CONCLUSIONS

ICD-10 codes for hyponatraemia in the DNRP have high specificity but very low sensitivity. Laboratory test results, not discharge diagnoses, should be used to ascertain hyponatraemia.

Use of the International Classification of Diseases, 9th revision, coding in identifying chronic hepatitis B virus infection in health system data: implications for national surveillance

OBJECTIVE

With increasing use electronic health records (EHR) in the USA, we looked at the predictive values of the International Classification of Diseases, 9th revision (ICD-9) coding system for surveillance of chronic hepatitis B virus (HBV) infection.

MATERIALS AND METHODS

The chronic HBV cohort from the Chronic Hepatitis Cohort Study was created based on electronic health records (EHR) of adult patients who accessed services from 2006 to 2008 from four healthcare systems in the USA. Using the gold standard of abstractor review to confirm HBV cases, we calculated the sensitivity, specificity, positive and negative predictive values using one qualifying ICD-9 code versus using two qualifying ICD-9 codes separated by 6 months or greater.

RESULTS

Of 1 652 055 adult patients, 2202 (0.1%) were confirmed as having chronic HBV. Use of one ICD-9 code had a sensitivity of 83.9%, positive predictive value of 61.0%, and specificity and negative predictive values greater than 99%. Use of two hepatitis B-specific ICD-9 codes resulted in a sensitivity of 58.4% and a positive predictive value of 89.9%.

DISCUSSION

Use of one or two hepatitis B ICD-9 codes can identify cases with chronic HBV infection with varying sensitivity and positive predictive values.

CONCLUSIONS

As the USA increases the use of EHR, surveillance using ICD-9 codes may be reliable to determine the burden of chronic HBV infection and would be useful to improve reporting by state and local health departments.

Identifying geographical regions serviced by hospitals to assess laboratory-based outcomes

OBJECTIVE

To define geographical regions (forward sortation areas; FSAs) in Southwestern Ontario, Canada from which patients would reliably present to a hospital with linked laboratory data if they developed adverse events related to medications dispensed in outpatient pharmacies.

DESIGN

Descriptive research.

SETTING

Forty-five hospitals in Southwestern Ontario, Canada, from 2003 to 2009.

PARTICIPANTS

Patients aged 66 years and older who received an outpatient prescription for any drug and presented to the emergency department in the subsequent 120 days.

MAIN OUTCOME MEASURE

The proportion of patients in a given FSA presenting to an emergency department at a hospital with linked laboratory data versus a hospital without linked laboratory data. To be included in the catchment area at least 90% of emergency department visits in an FSA must have occurred at laboratory-linked hospitals in a given year.

RESULTS

Over the study period, there were 649 713 emergency department visits by patients with recent prescription claims from pharmacies in 1 of 118 FSAs. In total, 141 302 of these patients presented to an emergency department at a laboratory-linked hospital. For the year 2003, 12 FSAs met our criteria to be in the catchment area and this number grew to 25 FSAs by the year 2009.

CONCLUSIONS

The relevant geographical regions for hospitals with linked laboratory data have been successfully identified. Studies can now be conducted using these well-defined areas to obtain reliable information on the incidence and absolute risk of presenting to hospital with laboratory abnormalities in older adults dispensed commonly prescribed medications in outpatient pharmacies.

Prevalence of hyponatremia on geriatric wards compared to other settings over four decades: a systematic review

Aim of the study was to analyze temporal trends in prevalence of hyponatremia over four decades in different settings. A systematic review of the literature from 1966 to 2009 yielded prevalences of hyponatremia, with standard errors (SE) and pooled estimated means (PEM), calculated by year and setting (geriatric, ICU, other hospital wards, psychiatric hospitals, nursing homes, outpatients). 53 studies were included. Prevalence of hyponatremia was stable from 1976 to 2006, and higher on geriatric wards accept for ICU: e.g. PEM prevalence of mild hyponatremia (serum sodium <135 mM) was 22.2% (95%CI 20.2-24.3) on geriatric wards, 6.0% (95%CI 5.9-6.1) on other hospital wards and 17.2% (SE 7.0) in one ICU-study; for severe hyponatremia (serum sodium<125 mM) these figures were 4.5% (95%CI 3.0-6.1), 0.8% (95%CI 0.7-0.8) and 10.3% (SE 5.6). In nursing homes PEM prevalence of mild hyponatremia was 18.8% (95%CI 15.6-22.2). The higher prevalence on geriatric wards could partly be explained by age-related changes in the regulation of serum sodium. Other underlying factors can be the presence of multiple diagnoses and the use of polypharmacy.

Pathophysiology, impact, and management of hyponatremia

Hyponatremia's effects can be insidious, particularly in patients with heart failure, cirrhosis, and pneumonia. Appreciating its prevalence in hospitalized patients, recognizing its symptoms, characterizing its etiology, and employing appropriate management promptly will help reduce morbidity and mortality among hyponatremic patients.

Validity of the International Classification of Diseases 10th revision code for hyperkalaemia in elderly patients at presentation to an emergency department and at hospital admission

OBJECTIVES

Evaluate the validity of the International Classification of Diseases, 10th revision (ICD-10) code for hyperkalaemia (E87.5) in two settings: at presentation to an emergency department and at hospital admission.

DESIGN

Population-based validation study.

SETTING

12 hospitals in Southwestern Ontario, Canada, from 2003 to 2010.

PARTICIPANTS

Elderly patients with serum potassium values at presentation to an emergency department (n=64 579) and at hospital admission (n=64 497).

PRIMARY OUTCOME

Sensitivity, specificity, positive-predictive value and negative-predictive value. Serum potassium values in patients with and without a hyperkalaemia code (code positive and code negative, respectively).

RESULTS

The sensitivity of the best-performing ICD-10 coding algorithm for hyperkalaemia (defined by serum potassium >5.5 mmol/l) was 14.1% (95% CI 12.5% to 15.9%) at presentation to an emergency department and 14.6% (95% CI 13.3% to 16.1%) at hospital admission. Both specificities were greater than 99%. In the two settings, the positive-predictive values were 83.2% (95% CI 78.4% to 87.1%) and 62.0% (95% CI 57.9% to 66.0%), while the negative-predictive values were 97.8% (95% CI 97.6% to 97.9%) and 96.9% (95% CI 96.8% to 97.1%). In patients who were code positive for hyperkalaemia, median (IQR) serum potassium values were 6.1 (5.7 to 6.8) mmol/l at presentation to an emergency department and 6.0 (5.1 to 6.7) mmol/l at hospital admission. For code-negative patients median (IQR) serum potassium values were 4.0 (3.7 to 4.4) mmol/l and 4.1 (3.8 to 4.5) mmol/l in each of the two settings, respectively.

CONCLUSIONS

Patients with hospital encounters who were ICD-10 E87.5 hyperkalaemia code positive and negative had distinct higher and lower serum potassium values, respectively. However, due to very low sensitivity, the incidence of hyperkalaemia is underestimated.

Evaluation of costs associated with tolvaptan-mediated length-of-stay reduction among heart failure patients with hyponatremia in the US, based on the EVEREST trial

BACKGROUND

The Efficacy of Vasopressin Antagonism in Heart Failure Outcome Study with Tolvaptan (EVEREST) trial showed that tolvaptan use improved heart failure (HF) signs and symptoms without serious adverse events.

OBJECTIVE

To evaluate the potential cost savings associated with tolvaptan usage among hospitalized hyponatremic HF patients.

METHODS

The Healthcare Cost and Utilization Project (HCUP) 2008 Nationwide Inpatient Sample (NIS) database was used to estimate hospital cost and length of stay (LOS), for diagnosis-related group (DRG) hospitalizations of adult (age ≥18 years) HF patients with complications and comorbidities or major complications and comorbidities. EVEREST trial data for patients with hyponatremia were used to estimate tolvaptan-associated LOS reductions. A cost offset model was constructed to evaluate the impact of tolvaptan on hospital cost and LOS, with univariate and multivariate Monte Carlo sensitivity analyses.

RESULTS

Tolvaptan use among hyponatremic EVEREST trial HF patients was associated with shorter hospital LOS than placebo patients (9.72 vs 11.44 days, respectively); 688,336 hospitalizations for HF DRGs were identified from the HCUP NIS database, with a mean LOS of 5.4 days and mean total hospital costs of $8415. Using an inpatient tolvaptan treatment duration of 4 days with a wholesale acquisition cost of $250 per day, the cost offset model estimated a LOS reduction among HF hospitalizations of 0.81 days and an estimated total cost saving of $265 per admission. Univariate and multivariate sensitivity analysis demonstrated that cost reduction associated with tolvaptan usage is consistent among variations of model variables.

CONCLUSIONS

The estimated LOS reduction and cost savings projected by the cost offset model suggest a clinical and economic benefit to tolvaptan use in hyponatremic HF patients.

STUDY LIMITATIONS

The EVEREST trial data may not generalize well to the US population. Clinical trial patient profiles and relative LOS reductions may not be applicable to real-world patient populations.

Validity of the International Classification of Diseases 10th revision code for hospitalisation with hyponatraemia in elderly patients

OBJECTIVE

To evaluate the validity of the International Classification of Diseases, 10th Revision (ICD-10) diagnosis code for hyponatraemia (E87.1) in two settings: at presentation to the emergency department and at hospital admission.

DESIGN

Population-based retrospective validation study.

SETTING

Twelve hospitals in Southwestern Ontario, Canada, from 2003 to 2010.

PARTICIPANTS

Patients aged 66 years and older with serum sodium laboratory measurements at presentation to the emergency department (n=64 581) and at hospital admission (n=64 499).

MAIN OUTCOME MEASURES

Sensitivity, specificity, positive predictive value and negative predictive value comparing various ICD-10 diagnostic coding algorithms for hyponatraemia to serum sodium laboratory measurements (reference standard). Median serum sodium values comparing patients who were code positive and code negative for hyponatraemia.

RESULTS

The sensitivity of hyponatraemia (defined by a serum sodium ≤132 mmol/l) for the best-performing ICD-10 coding algorithm was 7.5% at presentation to the emergency department (95% CI 7.0% to 8.2%) and 10.6% at hospital admission (95% CI 9.9% to 11.2%). Both specificities were greater than 99%. In the two settings, the positive predictive values were 96.4% (95% CI 94.6% to 97.6%) and 82.3% (95% CI 80.0% to 84.4%), while the negative predictive values were 89.2% (95% CI 89.0% to 89.5%) and 87.1% (95% CI 86.8% to 87.4%). In patients who were code positive for hyponatraemia, the median (IQR) serum sodium measurements were 123 (119-126) mmol/l and 125 (120-130) mmol/l in the two settings. In code negative patients, the measurements were 138 (136-140) mmol/l and 137 (135-139) mmol/l.

CONCLUSIONS

The ICD-10 diagnostic code for hyponatraemia differentiates between two groups of patients with distinct serum sodium measurements at both presentation to the emergency department and at hospital admission. However, these codes underestimate the true incidence of hyponatraemia due to low sensitivity.

Cost Issues in Hyponatremia

Purpose

To describe the morbidity and mortality associated with hyponatremia and its impact on health care costs and outcomes in the United States, describe the role of pharmacists in the overall management of hyponatremia, and identify and address cost and resource allocation issues.

Summary

Hyponatremia places a significant burden on overall hospital and health care costs. Underrecognition of the disorder and inappropriate hospital management can lead to worse outcomes, impacting length of stay (LOS), need for intensive care unit (ICU) admission, and clinical outcomes. Risk of mortality rises with increasing severity of hyponatremia, but even mild hyponatremia is associated with increased in-hospital mortality. The association with mortality is particularly robust in patients admitted to the hospital with cardiovascular disease and metastatic cancer. For patients admitted to the ICU, severe hyponatremia is a predictor of mortality. Elderly patients with admission hyponatremia face an especially poor prognosis. Resolving hyponatremia during hospitalization decreases the risk of mortality, suggesting that improved identification and aggressive monitoring may lead to more appropriate treatment. Pharmacoeconomic data can be utilized to support clinical decision-making in the management of hyponatremia by evaluating drug therapy and by monitoring hyponatremia development and therapeutic outcomes.

Conclusion:

Prompt recognition and optimal management of hyponatremia in hospitalized patients may reduce mortality and symptom severity, allow for less intensive care, decrease LOS and associated costs, and improve treatment of underlying comorbid conditions and quality of life. Pharmacists have a key role in optimizing the management of hyponatremia.

Risk of thiazide-induced hyponatremia in patients with hypertension

BACKGROUND

Although hyponatremia is a well-recognized complication of treatment with thiazide diuretics, the risk of thiazide-induced hyponatremia remains uncertain in routine care.

METHODS

We conducted a retrospective cohort study using a multicenter clinical research registry to identify 2613 adult outpatients that were newly treated for hypertension between January 1, 2000 and December 31, 2005 at 2 teaching hospitals in Boston, Massachusetts, and followed them for up to 10 years.

RESULTS

Two hundred twenty patients exposed to ongoing thiazide therapy were compared with 2393 patients who were not exposed. In the exposed group, 66 (30%) developed hyponatremia (sodium ≤130 mmol/L). The adjusted incidence rate of hyponatremia was 140 cases per 1000 person-years for patients treated with thiazides, compared with 87 cases per 1000 person-years in those without thiazides. Patients exposed to thiazides were more likely to develop hyponatremia (adjusted incidence rate ratio, 1.61; 95% confidence interval [CI], 1.15-2.25). There was no significant difference in the risk of hospitalizations associated with hyponatremia (adjusted rate ratio, 1.04; 95% CI, 0.46-2.32) or mortality (adjusted rate ratio, 0.41; 95% CI, 0.12-1.42). The number needed to harm (to result in one excess case of incident hyponatremia in 5 years) was 15.02 (95% CI, 7.88-160.30).

CONCLUSIONS

Approximately 3 in 10 patients exposed to thiazides who continue to take them develop hyponatremia.

Substance use disorders in Iraq and Afghanistan veterans in VA healthcare, 2001-2010: Implications for screening, diagnosis and treatment

BACKGROUND

The prevalence and correlates of alcohol use disorder (AUD) and drug use disorder (DUD) diagnoses in Iraq and Afghanistan veterans who are new users of Department of Veterans Affairs (VA) healthcare nationwide has not been evaluated.

METHODS

VA administrative data were used in retrospective cross-sectional descriptive and multivariable analyses to determine the prevalence and independent correlates of AUD and DUD in 456,502 Iraq and Afghanistan veterans who were first-time users of VA healthcare between October 15, 2001 and September 30, 2009 and followed through January 1, 2010.

RESULTS

Over 11% received substance use disorder diagnoses: AUD, DUD or both; 10% received AUD diagnoses, 5% received DUD diagnoses and 3% received both. Male sex, age < 25 years, being never married or divorced, and proxies for greater combat exposure were independently associated with AUD and DUD diagnoses. Of those with AUD, DUD or both diagnoses, 55-75% also received PTSD or depression diagnoses. AUD, DUD or both diagnoses were 3-4.5 times more likely in veterans with PTSD and depression (p < 0.001).

CONCLUSIONS

Post-deployment AUD and DUD diagnoses were more prevalent in subgroups of Iraq and Afghanistan veterans and were highly comorbid with PTSD and depression. Stigma and lack of universal screening may have reduced the number of DUD diagnoses reported. There is a need for improved screening and diagnosis of substance use disorders and increased availability of integrated treatments that simultaneously address AUD and DUD in the context of PTSD and other deployment-related mental health disorders.

A comparison of comorbidities obtained from hospital administrative data and medical charts in older patients with pneumonia

Background

The use of comorbidities in risk adjustment for health outcomes research is frequently necessary to explain some of the observed variations. Medical charts reviews to obtain information on comorbidities is laborious. Increasingly, electronic health care databases have provided an alternative for health services researchers to obtain comorbidity information. However, the rates obtained from databases may be either over- or under-reported. This study aims to (a) quantify the agreement between administrative data and medical charts review across a set of comorbidities; and (b) examine the factors associated with under- or over-reporting of comorbidities by administrative data.

Methods

This is a retrospective cross-sectional study of patients aged 55 years and above, hospitalized for pneumonia at 3 acute care hospitals. Information on comorbidities were obtained from an electronic administrative database and compared with information from medical charts review. Logistic regression was performed to identify factors that were associated with under- or over-reporting of comorbidities by administrative data.

Results

The prevalence of almost all comorbidities obtained from administrative data was lower than that obtained from medical charts review. Agreement between comorbidities obtained from medical charts and administrative data ranged from poor to very strong (kappa 0.01 to 0.78). Factors associated with over-reporting of comorbidities were increased length of hospital stay, disease severity, and death in hospital. In contrast, those associated with under-reporting were number of comorbidities, age, and hospital admission in the previous 90 days.

Conclusions

The validity of using secondary diagnoses from administrative data as an alternative to medical charts for identification of comorbidities varies with the specific condition in question, and is influenced by factors such as age, number of comorbidities, hospital admission in the previous 90 days, severity of illness, length of hospitalization, and whether inhospital death occurred. These factors need to be taken into account when relying on administrative data for comorbidity information.

Initial approach to the hyponatremic patient

Hyponatremia with cerebral symptoms is a medical emergency in which treatment delay may prove fatal. However, controversy prevails over which treatment is the best. This paper presents a practical and unified approach based on a literature study of the physiology of plasma [Na(+) ], the brain's response and clinical and experimental studies. Experimental and clinical studies were thoroughly reviewed. The literature was identified through MESH and free text search in the databases PubMed, Embase and Cochrane, and references in the literature. Cerebral water homeostasis is pivotal in hyponatremia. Prompt, repeated boluses of 2 ml/kg 3% saline constitute a rational treatment of symptomatic hyponatremia. After the initial correction, concern is mainly with avoiding overcorrection and osmotic demyelination. Plasma [Na(+)] is determined by the external balances of water and cations. The water balance must therefore be carefully monitored to counter the dramatic increase in plasma [Na(+)] that may result from brisk diuresis. Definitive treatment of hyponatremia should be directed toward its etiology. This can be challenging and the clinical application of traditional classifications based on hydration is difficult. Therefore, a practical approach is proposed based on the mechanisms of impaired urine dilution.

CONCLUSIONS

The conflict between previously opposing standpoints is gradually giving way to an emerging consensus: Prompt bolus treatment of symptomatic hyponatremia with hypertonic saline. After the initial treatment, overcorrection must be avoided. Definitive treatment should be directed toward the nature of the underlying disorder. An approach based on the mechanism governing the impaired urine dilution has been proposed.

Validation of coding algorithms for the identification of patients with primary biliary cirrhosis using administrative data

BACKGROUND

Large-scale epidemiological studies of primary biliary cirrhosis (PBC) have been hindered by difficulties in case ascertainment.

OBJECTIVE

To develop coding algorithms for identifying PBC patients using administrative data--a widely available data source.

METHODS

Population-based administrative databases were used to identify patients with a diagnosis code for PBC from 1994 to 2002. Coding algorithms for confirmed PBC (two or more of antimitochondrial antibody positivity, cholestatic liver biochemistry and/or compatible liver histology) were derived using chart abstraction data as the reference. Patients with a recorded PBC diagnosis but insufficient confirmatory data were classified as 'suspected PBC'.

RESULTS

Of 189 potential PBC cases, 119 (60%) had confirmed PBC and 28 (14%) had suspected PBC. The optimal algorithm including two or more uses of a PBC code had a sensitivity of 94% (95% CI 71% to 100%) and positive predictive values of 73% (95% CI 61% to 75%) for confirmed PBC, and 89% (95% CI 82% to 94%) for confirmed or suspected PBC. Sensitivity analyses revealed greater accuracy among women, and with the use of multiple data sources and one or more years of data. Inclusion of diagnosis codes for conditions frequently misclassified as PBC did not improve algorithm performance.

CONCLUSIONS

Administrative databases can reliably identify patients with PBC and may facilitate epidemiological investigations of this condition.

The critical link of hypervolemia and hyponatremia in heart failure and the potential role of arginine vasopressin antagonists

BACKGROUND

Hypervolemia and hyponatremia resulting from activation of the neurohormonal system and impairment of renal function are prominent features of decompensated heart failure. Both conditions share many pathophysiologic and prognostic features and each has been associated with increased morbidity and mortality. When both conditions coexist, therapeutic options are limited.

METHODS AND RESULTS

This review presents a concise digest of the pathophysiology, clinical significance, and pharmacological therapy of hyponatremia complicating heart failure with a special emphasis on vasopressin antagonists and their aquaretic effects in the absence of neurohormonal activation along with their ability to correct hyponatremia.

CONCLUSIONS

Hypervolemia and hyponatremia share many pathophysiologic and prognostic features in heart failure. Vasopressin antagonists provide a viable option for their management and a potentially unique role when both conditions coexists.

Identification of exacerbations in obstructive lung disease through biomarkers

Inflammation has been identified as an important factor for disease exacerbation in obstructive lung disease. In this study, we used neutrophil and eosinophil counts as biomarkers for exacerbation in obstructive lung disease. We conducted a case-control study within a cohort of patients frequenting an outpatient clinic of Respiratory Medicine using data from the Utrecht Patient Oriented Database (UPOD). Cases were patients with a hospital admission for obstructive lung disease in 2005. For each case, one control patient was sampled from the same study base. We identified 143 cases (118 patients with chronic obstructive pulmonary disease and 25 asthma patients) and 143 controls. Admission was associated with both neutrophilia (adjusted odds ratio (OR) 4.3; 95% confidence interval (CI) 2.2-8.5), and eosinophilia (adjusted OR 2.6; 95% CI 1.1-6.2). The association with eosinophilia was only seen in asthma patients. In conclusion, neutrophil and eosinophil counts seem to be useful biomarkers for identifying exacerbations in pharmacoepidemiological studies on obstructive lung disease.

VA mental health services utilization in Iraq and Afghanistan veterans in the first year of receiving new mental health diagnoses

Little is known about mental health services utilization among Iraq and Afghanistan veterans receiving care at Department of Veterans Affairs (VA) facilities. Of 49,425 veterans with newly diagnosed posttraumatic stress disorder (PTSD), only 9.5% attended 9 or more VA mental health sessions in 15 weeks or less in the first year of diagnosis. In addition, engagement in 9 or more VA treatment sessions for PTSD within 15 weeks varied by predisposing variables (age and gender), enabling variables (clinic of first mental health diagnosis and distance from VA facility), and need (type and complexity of mental health diagnoses). Thus, only a minority of Iraq and Afghanistan veterans with new PTSD diagnoses received a recommended number and intensity of VA mental health treatment sessions within the first year of diagnosis.

SIADH and hyponatraemia: foreword

Hyponatraemia is common, affecting about one in five of all hospitalized patients. Minor degrees of chronic hyponatraemia cause cognitive and motor impairment, and severe hyponatraemia is associated with substantial morbidity and mortality. Syndrome of inappropriate antidiuretic hormone secretion (SIADH) is a common cause of hyponatraemia and is often poorly understood and inappropriately treated. Clinical evaluation and simple biochemical assessment should guide management. The introduction of vasopressin antagonists, or vaptans, into clinical practice heralds the beginning of a new and exciting era for this important group of disorders.

Epidemiology of hyponatremia

Hyponatremia is the most common electrolyte abnormality encountered in clinical practice with wide-ranging prognostic implications in a variety of conditions. This review summarizes the available literature on the epidemiology of hyponatremia in both hospitalized and ambulatory-based patients. Particular attention is given to hyponatremia in the geriatric population, drug-induced hyponatremia, exercise-associated hyponatremia, and the medical costs of hyponatremia. The frequency and outcomes of hyponatremia in congestive heart failure, cirrhosis, pneumonia, and human immunodeficiency virus infection also are reviewed. Although the knowledge on hyponatremia has expanded in the past few decades, the disorder largely remains an underdiagnosed condition. Substantial additional work is needed to improve the awareness of hyponatremia among medical professionals. The advent of vasopressin-receptor antagonists as a plausible treatment option for some forms of euvolemic and hypervolemic hyponatremia now offers the opportunity to gain further insights into the prognostic impact of hyponatremia and its management in various clinical settings.

Trends and risk factors for mental health diagnoses among Iraq and Afghanistan veterans using Department of Veterans Affairs health care, 2002-2008

OBJECTIVES

We sought to investigate longitudinal trends and risk factors for mental health diagnoses among Iraq and Afghanistan veterans.

METHODS

We determined the prevalence and predictors of mental health diagnoses among 289,328 Iraq and Afghanistan veterans entering Veterans Affairs (VA) health care from 2002 to 2008 using national VA data.

RESULTS

Of 289,328 Iraq and Afghanistan veterans, 106,726 (36.9%) received mental health diagnoses; 62,929 (21.8%) were diagnosed with posttraumatic stress disorder (PTSD) and 50 432 (17.4%) with depression. Adjusted 2-year prevalence rates of PTSD increased 4 to 7 times after the invasion of Iraq. Active duty veterans younger than 25 years had higher rates of PTSD and alcohol and drug use disorder diagnoses compared with active duty veterans older than 40 years (adjusted relative risk = 2.0 and 4.9, respectively). Women were at higher risk for depression than were men, but men had over twice the risk for drug use disorders. Greater combat exposure was associated with higher risk for PTSD.

CONCLUSIONS

Mental health diagnoses increased substantially after the start of the Iraq War among specific subgroups of returned veterans entering VA health care. Early targeted interventions may prevent chronic mental illness.

Trends in hospitalizations for AIDS-associated Pneumocystis jirovecii Pneumonia in the United States (1986 to 2005)

BACKGROUND

Although hospitalizations for AIDS-associated Pneumocystis jirovecii pneumonia (PCP) in the United States have decreased since the introduction of chemoprophylaxis and potent combination antiretroviral therapy (ART), PCP remains an important cause of illness and death among AIDS patients.

METHODS

We analyzed trends in AIDS-associated PCP hospital discharges using the National Hospital Discharge Surveys between 1986 and 2005.

RESULTS

An estimated 539 million patients were discharged from hospitals between 1986 and 2005, of whom an estimated 312,411 had AIDS-associated PCP. The proportion of patients discharged from the hospital with AIDS-associated PCP decreased from 31% before the introduction of chemoprophylaxis (1986 to 1989) to 17% with chemoprophylaxis (1990 to 1995) and subsequently to 9% after the introduction of ART in 1996 (p < 0.001). Mortality from AIDS-associated PCP decreased from 21 to 16% and subsequently to 7% between these three time periods (p < 0.001). Among those who received mechanical ventilation, mortality decreased from 79% in the prechemoprophylaxis era to 31% in the ART era (p < 0.001) alongside an increase (from 5 to 11%) in the use of mechanical ventilation. We also observed a shift in the population at-risk for PCP over time: a greater proportion of black people, women, and people from Southern states were affected (all p < 0.001).

CONCLUSIONS

While there have been significant reductions in hospitalizations and hospital mortality for AIDS-associated PCP over the last 20 years, these reductions have not been homogenous across demographic subpopulations and geographic regions and point to new at-risk populations. Furthermore, mortality in severe cases of PCP that require mechanical ventilation has improved substantially.

Measuring quality of care in syncope: case definition affects reported electrocardiogram use but does not bias reporting

OBJECTIVES

The objective was to calculate agreement between syncope as a reason for visiting (RFV) an emergency department (ED) and as a discharge diagnosis (International Classification of Diseases, Ninth Revision, Clinical Modification [ICD-9]), to determine whether syncope case definition biases reported electrocardiogram (ECG) usage, a national quality measure.

METHODS

The authors analyzed the ED portion of the National Hospital Ambulatory Medical Care Survey (NHAMCS), 1993-2004, for patients age >or=18 years. A visit was defined as being for syncope if it received one of three RFV or ICD-9 codes. Agreement between RFV and ICD-9 codes was calculated, and the percentages of syncope patients (RFV vs. ICD-9) who had an ECG were compared using chi-square and multivariate logistic regression.

RESULTS

Raw agreement between syncope as an RFV and as an ICD-9 diagnosis code was 30.1% (95% confidence interval [CI] = 32.6% to 35.5%), representing only moderate agreement beyond chance (kappa = 0.50). ECG utilization was lower among visits defined by RFV (64.1%; 95% CI = 62.0% to 66.3%) than for ICD-9 diagnosis (73.6%; 95% CI = 71.4% to 75.8%). There was no meaningful variation in adjusted ECG use by patient, visit, or hospital characteristics between case definitions. Adjusted ECG use was lower under both case definitions among female patients and discharged patients and increased with age (p < 0.05).

CONCLUSIONS

Despite only moderate agreement, syncope case definition should not bias reported ECG rate by patient, visit, or hospital characteristics. Among ED patients with syncope, ECG is performed less frequently in women, a potentially important disparity.

Hyponatremia in heart failure

Hyponatremia is the most common electrolyte abnormality found in hospitalized patients with heart failure. It may occur in patients who have hypovolemic, hypervolemic, or euvolemic state. It is usually not corrected by available therapies. It is a major predictor of prognosis, and correction of hyponatremia can be effectively accomplished by vasopressin antagonists. However, it still remains to be seen whether the normalization of serum sodium with vasopressin antagonists will also lead to an improved long-term prognosis.

Sensitivity of International Classification of Diseases codes for hyponatremia among commercially insured outpatients in the United States

Background

Administrative claims are a rich source of information for epidemiological and health services research; however, the ability to accurately capture specific diseases or complications using claims data has been debated. In this study, the authors examined the validity of International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) diagnosis codes for the identification of hyponatremia in an outpatient managed care population.

Methods

We analyzed outpatient laboratory and professional claims for patients aged 18 years and older in the National Managed Care Benchmark Database from Integrated Healthcare Information Services. We obtained all claims for outpatient serum sodium laboratory tests performed in 2004 and 2005, and all outpatient professional claims with a primary or secondary ICD-9-CM diagnosis code of hyponatremia (276.1).

Results

A total of 40,668 outpatient serum sodium laboratory results were identified as hyponatremic (serum sodium < 136 mmol/L). The sensitivity of ICD-9-CM codes for hyponatremia in outpatient professional claims within 15 days before or after the laboratory date was 3.5%. Even for severe cases (serum sodium ≤ 125 mmol/L), sensitivity was < 30%. Specificity was > 99% for all cutoff points.

Conclusion

ICD-9-CM codes in administrative data are insufficient to identify hyponatremia in an outpatient population.

Medical costs of abnormal serum sodium levels

An abnormal serum sodium level is the most common electrolyte disorder in the United States and can have a significant impact on morbidity and mortality. The direct medical costs of abnormal serum sodium levels are not well understood. The impact of hyponatremia and hypernatremia on 6-mo and 1-yr direct medical costs was examined by analyzing data from the Integrated HealthCare Information Services National Managed Care Benchmark Database. During the period analyzed, there were 1274 patients (0.8%) with hyponatremia (serum sodium <135 mmol/L), 162,829 (97.3%) with normal serum sodium levels, and 3196 (1.9%) with hypernatremia (>145 mmol/L). Controlling for age, sex, region, and comorbidities, hyponatremia was a significant independent predictor of costs at 6 mo (41.2% increase in costs; 95% confidence interval, 30.3% to 53.0%) and at 1 yr (45.7% increase; 95% confidence interval, 34.2% to 58.2%). Costs associated with hypernatremia were not significantly different from those incurred by patients with normal serum sodium. In conclusion, hyponatremia is a significant independent predictor of 6-mo and 1-yr direct medical costs.

International classification of diseases codes showed modest sensitivity for detecting community-acquired pneumonia

OBJECTIVE

To estimate the sensitivity of International Classification of Diseases (ICD-9-CM) coding for detecting hospitalized community-acquired pneumonia and to assess possible determinants for misclassification.

STUDY DESIGN AND SETTING

Based on microbiological analysis data, 293 patients with a principal diagnosis of community-acquired pneumonia at seven hospitals in the Netherlands were assigned to three categories (pneumococcal pneumonia, pneumonia with other organism, or pneumonia with no organism specified). For these patients, the assigned principal and secondary ICD-9-CM codes in the hospital discharge record were retrieved and the corresponding sensitivity was calculated. Furthermore, pneumonia-related patient characteristics were compared between correctly and incorrectly coded subjects.

RESULTS

The overall sensitivity was 72.4% for the principal code and 79.5% for combined principal and secondary codes. For pneumococcal pneumonia (ICD-9-CM code 481) and pneumonia with specified organism (ICD-9-CM code 482-483), the sensitivities were 35% and 18.3%, respectively. Patient characteristics were not significantly different between correctly and incorrectly coded subjects except for duration of hospital stay, which correlated negatively with coding sensitivity (P=0.01).

CONCLUSION

ICD-9-CM codes showed modest sensitivity for detecting community-acquired pneumonia in hospital administrative databases, leaving at least one quarter of pneumonia cases undetected. Sensitivity decreased with longer duration of hospital stay.