Depletion-of-susceptibles bias in influenza vaccine waning studies: how to ensure robust results

Vaccine effectiveness studies are subject to biases due to depletion-of-persons at risk of infection, or at especially high risk of infection, at different rates from different groups (depletion-of-susceptibles bias), a problem that can also lead to biased estimates of waning effectiveness, including spurious inference of waning when none exists. An alternative study design to identify waning is to study only vaccinated persons, and compare for each day the incidence in persons with earlier or later dates of vaccination to assess waning in vaccine protection as a function of vaccination time (namely whether earlier vaccination would result in lower subsequent protection compared to later vaccination). Prior studies suggested under what conditions this alternative would yield correct estimates of waning. Here we define the depletion-of-susceptibles process formally and show mathematically that for influenza vaccine waning studies, a randomised trial or corresponding observational study that compares incidence at a specific calendar time among individuals vaccinated at different times before the influenza season begins will not be vulnerable to depletion-of-susceptibles bias in its inference of waning as a function of vaccination time under the null hypothesis that none exists, and will - if waning does actually occur - underestimate the extent of waning. Such a design is thus robust in the sense that a finding of waning in that inference framework reflects actual waning of vaccine-induced immunity. We recommend such a design for future studies of waning, whether observational or randomised.

Safety of zoster vaccine in adults from a large managed-care cohort: a Vaccine Safety Datalink study

OBJECTIVES

The aim of this study was to examine a large cohort of adults who received the zoster vaccine for evidence of an increased risk of prespecified adverse events requiring medical attention.

DESIGN

Two self-comparison approaches, including a case-centred approach and a self-controlled case series (SCCS) analysis were used.

SETTING

Eight managed-care organizations participating in the Vaccine Safety Datalink project in the United States.

SUBJECTS

A total of 193 083 adults aged 50 and older receiving a zoster vaccine from 1 January 2007 to 31 December 2008 were included.

MAIN OUTCOME MEASURES

Prespecified adverse events were identified by aggregated International Classification of Diseases, Ninth Revision (ICD-9) codes in automated health plan datasets.

RESULTS

The risk of allergic reaction was significantly increased within 1-7 days of vaccination [relative risk = 2.13, 95% confidence interval (CI): 1.87-2.40 by case-centred method and relative rate = 2.32, 95% CI: 1.85-2.91 by SCCS]. No increased risk was found for the following adverse event groupings: cerebrovascular events; cardiovascular events; meningitis; encephalitis; and encephalopathy; and Ramsay-Hunt syndrome and Bell's palsy.

CONCLUSIONS

The results of this study support the findings from the prelicensure clinical trials, providing reassurance that the zoster vaccine is generally safe and well-tolerated with a small increased risk of allergic reactions in 1-7 days after vaccination.

Phase II trial of nab-paclitaxel as first-line therapy of hormone refractory metastatic prostate cancer (HRPC)

5152

Background: Many patients with hormone refractory prostate cancer have poor tolerance to treatment. Docetaxel chemotherapy was shown to improve survival but has substantial toxicity, requires steroid administration, may cause poorly reversible neuropathy and requires long infusion times, all limiting its use. Nab-paclitaxel, an albumin-bound nanopaticle form of paclitaxel, delivers paclitaxel without steroids, requires only 30 minutes infusion time and has favorable toxicity profile that may be more tolerable but effective in patients with prostate cancer. The goal of this study was to evaluate the efficacy and toxicity of nab-paclitaxel in first line chemotherapy of men with castration resistant prostate cancer. Methods: nab-paclitaxel was given iv100 mg/m2 weekly x 3 of 4 weeks cycles. Main eligibility criteria include: hormone refractory metastatic prostate cancer, no prior chemotherapy, performance status 0–2. Primary endpoint was efficacy based on prostate-specific antigen (PSA) response. PSA response was PSA decrease of >50%, progressive disease (PD) was PSA increase of >25%, stable disease (SD) was <25% PSA increase or <50% decrease sustained longer that 8 weeks. Results: There are 38 patients enrolled, 35 were evaluable for response. Median age was 71 years old (range 57–86). One patient discontinued the treatment after 1 infusion due to toxicity (elevated ALT). PSA response was seen in 9 (25%) patients and SD in 15 patients (43%), with an overall response rate of 25% and clinical benefit of 68%. Seven patients received treatment for ≥ 6 months with minimal toxicity (range 6–10 months). Grade 3 related hematologic toxicity was reported in 7 (18%) patients (4 anemia, 4 neutropenia), grade 3 related non-hematologic toxicity was reported in 6 patients (1 hypokalemia, 1 muscle weakness, 2 fatigue, 1 fever, 1 neuropathy, 1 ALT elevation). Conclusions: Nab-paclitaxel has activity in patients with metastatic hormone refractory prostate cancer. This regimen was well tolerated, and may be useful in patients who are not suitable candidates for docetaxel based therapy.

[Table: see text]

Screening differences and risk of cervical cancer in inflammatory bowel disease

BACKGROUND

Cervical cancer risk is high among immune suppressed women.

AIM

To evaluate inflammatory bowel disease (IBD) with medications and risk of cervical cancer.

METHODS

Members of Kaiser Permanente Northern California (KPNC), 15-68 years from 1996 to 2006 with IBD were compared with age-matched women without IBD. Cervical cancer was ascertained using the KPNC Cancer Registry. IBD medications of interest were aminosalicylates (ASA), corticosteroids, immune modulators and infliximab. Odds of cervical cancer were analysed with adjusted logistic regression. The prevalence of Pap smear testing was compared using a log binomial model.

RESULTS

Ten cervical cancer cases occurred among 1165 women with IBD and 72 cancers among 12 124 controls. The adjusted odds ratio (OR) of IBD with risk of cervical cancer was 1.45 [95% confidence interval (CI) 0.74-2.84]. Medication ORs were 1.65 for ASA, 2.79 for corticosteroids and 3.45 for immune modulators (all P > 0.05). No cancer case used infliximab. The adjusted absolute increase in Pap smears among IBD women compared to women without IBD was 4% (95% CI 2-5%).

CONCLUSIONS

Although a trend of elevated risk for cervical cancer with IBD and IBD medications was observed, it was not statistically significant. Regular cervical cancer screening for women with IBD is recommended.

The prevalence of clinically recognized obsessive-compulsive disorder in a large health maintenance organization

OBJECTIVE

Little is known about the prevalence of obsessive-compulsive disorder (OCD) as recognized in clinical settings. The authors report data on the prevalence of clinically recognized OCD in a large, integrated, group practice health maintenance organization (HMO).

METHOD

The authors examined the database of outpatient diagnoses for the 1.7 million people (age >or=6) in the San Francisco Bay Area and Sacramento who were continuously enrolled in Kaiser Permanente from May 1995 through April 1996. OCD diagnoses were confirmed by chart review.

RESULTS

The 1-year prevalence of clinically recognized OCD was 84/100,000 (95% confidence interval: 80-89/100,000), or 0.084%. It varied among the 19 clinics within the HMO but was nowhere higher than 150/100,000. Prevalence was higher among women than among men but was higher among boys than among girls. Above age 65, OCD prevalence decreased markedly in both genders. Period prevalence rates increased by 60% as the length of the study period doubled from 1 to 2 years, more than would be expected for a chronic disease requiring regular care. About three-quarters of both children and adults with OCD had comorbid psychiatric diagnoses; major depression was common in both groups.

CONCLUSIONS

Although previously reported prevalences of 1%-3% from community studies may have included many transient or misclassified cases of OCD not requiring treatment, the very low prevalence of clinically recognized OCD in this population suggests that many individuals suffering from OCD are not receiving the benefits of effective treatment.

Pharmacotherapy of obsessive-compulsive disorder in a health maintenance organization

The adequacy of pharmacotherapy for patients with obsessive-compulsive disorder (OCD) in a large, prepaid HMO was studied. An analysis was made of the computerized records for December 1, 1994, through April 30, 1998, for members of a Kaiser Permanente plan in northern California who were six years of age or older and had had continuous membership during an index year (May 1, 1995, to April 30, 1996) (1,728 million members). A total of 880 adults and 168 children and adolescents with chart-review-confirmed OCD and a pharmacy benefit were identified. The percentage of patients with an adequate drug trial, defined as > or = 56 days of continuous treatment with a serotonin-reuptake inhibitor or phenelzine at dosages at or above established minimal effective dosages, was determined. Forty-three percent of the adults and 28% of the children and adolescents who were newly diagnosed with OCD in the index year had an adequate trial of medication in the year after their first visit for OCD. By the second six months after the index year, only 75.2% of newly treated adults and 60.9% of newly treated children and adolescents continuing in the health plan filled at least one anti-OCD prescription. During the second follow-up year, these figures fell to 60.4% and 38.9%, respectively. Continuing-care patients filling a prescription in the index year were more likely than newly diagnosed patients to fill prescriptions in the two-year follow-up period, but their treatment still decreased substantially. Despite the typically chronic course of OCD, many patients with OCD who were enrolled in a large HMO appeared not to receive an adequate trial of pharmacotherapy or ongoing pharmacotherapy.

Efficacy of nurse telehealth care and peer support in augmenting treatment of depression in primary care

BACKGROUND

Primary care treatment of depression needs improvement.

OBJECTIVE

To evaluate the efficacy of 2 augmentations to antidepressant drug treatment.

DESIGN

Randomized trial comparing usual care, telehealth care, and telehealth care plus peer support; assessments were conducted at baseline, 6 weeks, and 6 months.

SETTING

Two managed care adult primary care clinics.

PARTICIPANTS

A total of 302 patients starting antidepressant drug therapy.

INTERVENTIONS

For telehealth care: emotional support and focused behavioral interventions in ten 6-minute calls during 4 months by primary care nurses; and for peer support: telephone and in-person supportive contacts by trained health plan members recovered from depression.

MAIN OUTCOME MEASURES

For depression: the Hamilton Depression Rating Scale and the Beck Depression Inventory; and for mental and physical functioning: the SF-12 Mental and Physical Composite Scales and treatment satisfaction.

RESULTS

Nurse-based telehealth patients with or without peer support more often experienced 50% improvement on the Hamilton Depression Rating Scale at 6 weeks (50% vs 37%; P =.01) and 6 months (57% vs 38%; P =.003) and on the Beck Depression Inventory at 6 months (48% vs 37%; P =. 05) and greater quantitative reduction in symptom scores on the Hamilton scale at 6 months (10.38 vs 8.12; P =.006). Telehealth care improved mental functioning at 6 weeks (47.07 vs 42.64; P =.004) and treatment satisfaction at 6 weeks (4.41 vs 4.17; P =.004) and 6 months (4.20 vs 3.94; P =.001). Adding peer support to telehealth care did not improve the primary outcomes.

CONCLUSION

Nurse telehealth care improves clinical outcomes of antidepressant drug treatment and patient satisfaction and fits well within busy primary care settings.

Comparing the medical expenses of children with Medicaid and commercial insurance in an HMO

BACKGROUND

In recent years, growing numbers of children with Medicaid have been enrolled in managed care plans nationwide. Yet, large, commercial managed care plans are increasingly discontinuing their participation in Medicaid because of low Medicaid payment rates.

OBJECTIVE

To compare the healthcare utilization and costs of children with Medicaid and children with commercial insurance within the same health maintenance organization (HMO).

STUDY DESIGN

Retrospective study using electronically captured cost and utilization data.

PATIENTS AND METHODS

We compared the healthcare utilization and costs of children with Medicaid (n = 42,636) and children with commercial insurance (n = 159,651) who were members of the same large, nonprofit HMO at any time between January 1, 1995, and December 31, 1997. Medicaid children were grouped as income eligible, medically needy, and blind or disabled.

RESULTS

The unadjusted costs of income-eligible, Medicaid-insured children were not significantly different from those of commercially insured children. The medically needy were $25 per month more expensive than commercially insured children (P = 0.02), and the blind or disabled were $213 per month more expensive (P < .01). After adjusting for age and sex, income-eligible children were $5 per month more expensive than children with commercial insurance (P = .07), the medically needy were $20 per month more expensive (P = .02), and the blind or disabled were $216 per month more expensive (P < .01).

CONCLUSIONS

The costs of income-eligible, Medicaid-insured children in this HMO were similar to those of commercially insured children, but the costs for the medically needy and the blind and disabled were substantially higher.

The cost of health conditions in a health maintenance organization

In this retrospective cohort analysis of all adults who were members of Kaiser Permanente, Northern California, between July 1995 and June 1996 (N = 2,076,303), the authors estimated the prevalence, average annual costs per person, and percentage of total direct medical expenditures attributable to each of 25 chronic and acute conditions. Ordinary least squares regression was used to adjust for age, gender, and comorbidities. The costs attributable to the 25 conditions accounted for 78 percent of the health maintenance organization's total direct medical expense for this age-group. Injury accounted for a higher proportion (11.5 percent) of expenditures than any other single condition. Three cardiovascular conditions--ischemic heart disease, hypertension, and congestive heart failure--together accounted for 17 percent of direct medical expense and separately accounted for 6.8 percent, 5.7 percent, and 4.0 percent, respectively. Renal failure ($22,636), colorectal cancer ($10,506), pneumonia ($9,499), and lung cancer ($8,612) were the most expensive conditions per person per year.

Efficacy, safety and immunogenicity of heptavalent pneumococcal conjugate vaccine in children. Northern California Kaiser Permanente Vaccine Study Center Group

OBJECTIVE

To determine the efficacy, safety and immunogenicity of the heptavalent CRM197 pneumococcal conjugate vaccine against invasive disease caused by vaccine serotypes and to determine the effectiveness of this vaccine against clinical episodes of otitis media.

METHODS

The Wyeth Lederle Heptavalent CRM197 (PCV) was given to infants at 2, 4, 6 and 12 to 15 months of age in a double blind trial; 37,868 children were randomly assigned 1:1 to receive either the pneumococcal conjugate vaccine or meningococcus type C CRM197 conjugate. The primary study outcome was invasive disease caused by vaccine serotype. Other outcomes included overall impact on invasive disease regardless of serotype, effectiveness against clinical otitis media visits and episodes, impact against frequent and severe otitis media and ventilatory tube placement. In addition the serotype-specific efficacy against otitis media was estimated in an analysis of spontaneously draining ears.

RESULTS

In the interim analysis in August, 1998, 17 of the 17 cases of invasive disease caused by vaccine serotype in fully vaccinated children and 5 of 5 of partially vaccinated cases occurred in the control group for a vaccine efficacy of 100%. Blinded case ascertainment was continued until April, 1999. As of that time 40 fully vaccinated cases of invasive disease caused by vaccine serotype had been identified, all but 1 in controls for an efficacy of 97.4% (95% confidence interval, 82.7 to 99.9%), and 52 cases, all but 3 in controls in the intent-to-treat analysis for an efficacy of 93.9% (95% confidence interval, 79.6 to 98.5%). There was no evidence of any increase of disease caused by nonvaccine serotypes. Efficacy for otitis media against visits, episodes, frequent otitis and ventilatory tube placement was 8.9, 7.0, 9.3 and 20.1% with P < 0.04 for all. In the analysis of spontaneously draining ears, serotype-specific effectiveness was 66.7%.

CONCLUSION

This heptavalent pneumococcal conjugate appears to be highly effective in preventing invasive disease in young children and to have a significant impact on otitis media.

Alcohol drinking patterns and medical care use in an HMO setting

The objective of this study was to examine the association of medical care use (outpatient visits and hospitalization) with alcohol drinking patterns in a large health maintenance organization (HMO). Data were gathered from a random sample of 10,292 adult respondents through a telephone survey conducted between June 1994 and February 1996. Findings indicate that current nondrinkers with no past history of drinking had higher rates of outpatient visits and hospitalizations than current drinkers. Among current drinkers, medical care use declined slightly as drinking levels increased. Among nondrinkers, those with a drinking history exhibited significantly higher use of outpatient visits and hospital care than nondrinkers with no drinking history and current drinkers. Controlling for demographic and socioeconomic factors, health status, and common medical conditions in multivariate analyses suggests that nondrinkers with a drinking history use more services because they are sicker than other nondrinkers or current drinkers.

Drinking patterns and problems of the "stably insured": a study of the membership of a health maintenance organization

OBJECTIVE

This article describes drinking patterns and examines the prevalence of heavy drinking and alcohol problems, and their association with other behavioral and social problems within the membership of a health maintenance organization, a setting in which increasing numbers of Americans receive services.

METHOD

The sample is representative of the stably insured membership of the Northern California Region of Kaiser Permanente Medical Care Program; i.e., those who have been insured continuously under that plan for 30 months or longer. A telephone survey of the adult membership (N = 10,292) was conducted between June 1994 and February 1996.

RESULTS

As in other studies, health and mental health status and smoking were related to drinking levels, with symptoms higher for those in the heaviest drinking group. However, in contrast to studies of those using medical services, demographic characteristics (e.g., young age) were not associated with heavy drinking in this population. When controlling for drug use and drinking, however, women and those reporting any mental health symptom were more likely to report alcohol problems.

CONCLUSIONS

Findings suggest that in private managed care populations, particular behavioral indicators may be more important than demographic characteristics in screening for problem drinkers. The identification of individuals who report a mental health symptom, who drink a large number of drinks occasionally or who report any drug use may be important in a health maintenance approach to prevention and case finding.

Evaluating hypertension control in a managed care setting

BACKGROUND

We conducted a retrospective cohort study on a random sample of adult patients with hypertension in a large health maintenance organization to assess the feasibility of documenting blood pressure (BP) control and to compare different measures for defining BP control.

METHODS

Three criteria for BP control were assessed: systolic BP less than 140 mm Hg; diastolic BP less than 90 mm Hg; and combined BP control, with systolic BP less than 140 mm Hg and diastolic BP less than 90 mm Hg. Four methods of assessing hypertension control by the above criteria were examined: proportion of patients with BP under control at 75% and 50% or more of their office visits; the mean of all pressures during the study period; and the BP from the last visit during the study period.

RESULTS

The proportion of patients meeting each criterion for control was similar whether we used the mean BP for all visits, the last recorded BP, or control at 50% or more of visits. Control rates were substantially lower when the more stringent assessment, 75% of visits, was used. The proportion of patients with combined BP control at 75% or more of their visits was half that of the other methods.

CONCLUSIONS

In this health maintenance organization population, results with the use of the simplest approach, the last BP measurement recorded, were similar to results with the mean BP. Our findings indicate that evaluation of BP control in a large health maintenance organization will find substantial room for improvement, and clinicians should be encouraged to be more aggressive in their management of hypertension, especially with regard to the systolic BP, which until recent years has been underemphasized.

Safety and immunogenicity of heptavalent pneumococcal CRM197 conjugate vaccine in infants and toddlers

OBJECTIVES

The objectives of this study were (1) to determine the safety and immunogenicity of heptavalent pneumococcal CRM197 conjugate (PNCRM7) vaccine in infants and (2) to determine the effect of concurrent hepatitis B immunization during the primary series and the effect of concurrent diphtheria and tetanus toxoid and acellular pertussis [DTaP (ACEL-IMUNE)] and conjugate CRM197 Haemophilus influenzae type b [HbOC (HibTITER) immunization at time of the booster dose on the safety and immunogenicity of PNCRM7and these other concurrently administered vaccines.

METHODS

This was a randomized double-blinded study in 302 healthy infants in the Northern California Kaiser Permanente (NCKP) Health Plan. Infants received either PNCRM7 vaccine or meningococcal group C conjugate vaccine as a control at 2, 4 and 6 months of age and a booster at 12 to 15 months of age. Study design permitted the evaluation of immunology and safety of concurrent administration of routine vaccines. Antibody titers were determined on blood samples drawn before and 1 month after the primary series and the booster dose.

RESULTS

After the third dose of PNCRM7 geometric mean concentrations (GMCs) ranged from 1.01 for serotype 9V to 3.72 microg/ml for serotype 14. More than 90% of all subjects had a post-third dose titer of > or =0.15 microg/ml for all serotypes, and the percentage of infants with a post-third dose titer of > or =1.0 microg/ml ranged from 51% for type 9V to 89% for type 14. After the PNCRM7 booster dose, the GMCs of all seven serotypes increased significantly over both post-Dose 3 and pre-Dose 4 antibody levels. In the primary series there were no significant differences in GMCs of pneumococcal antibodies between the subjects given PN-CRM7 alone or concurrently with hepatitis B vaccine. At the toddler dose concurrent administration of PNCRM7 and DTaP and HbOC resulted in a near conventional threshold for statistical significance of a post-Dose 4 GMC for serotype 23F [alone 6.75 mirog/ml vs. concurrent 4.11 microg/ml (P = 0.057)] as well as significantly lower antibody GMCs for H. influenza polyribosylribitol phosphate, diphtheria toxoid, pertussis toxin and filamentous hemagglutinin. For all antigens there were no differences between study groups in defined antibody titers that are considered protective.

CONCLUSION

We conclude that PNCRM7 vaccine was safe and immunogenic. When this vaccine was administered concurrently at the booster dose with DTaP and HbOC vaccines, lower antibody titers were noted for some of the antigens when compared with the antibody response when PNCRM7 was given separately. Because the GMCs of the booster responses were all generally high and all subjects achieved similar percentages above predefined antibody titers, these differences are probably not clinically significant.

Mental disorders and disability among patients in a primary care group practice

OBJECTIVE

This article examines social and occupational disability associated with several DSM-IV mental disorders in a group of adult primary care outpatients.

METHOD

The subjects were 1,001 primary care patients (aged 18-70 years) in a large health maintenance organization. Data on each patient's sociodemographic characteristics and functional disability, including scores on the Sheehan Disability Scale, were collected at the time of a medical visit. A structured diagnostic interview for current DSM-IV disorders was then completed by a mental health professional over the telephone within 4 days of the visit.

RESULTS

The most prevalent disorders were phobias (7.7%), major depressive disorder (7.3%), alcohol use disorders (5.2%), generalized anxiety disorder (3.7%), and panic disorder (3.0%). A total of 8.3% of the patients met the criteria for more than one mental disorder. The proportion of patients with co-occurring mental disorders varied by index disorder from 50.0% (alcohol use disorder) to 89.2% (generalized anxiety disorder). Compared with patients who had a single mental disorder, patients with co-occurring disorders reported significantly more disability in social and occupational functioning. After adjustment for other mental disorders and demographic and general health factors, compared with patients with no mental disorder, only patients with major depressive disorder, bipolar disorder, phobias, and substance use disorders had significantly increased disability, as measured by the Sheehan Disability Scale.

CONCLUSIONS

Primary care patients with more than one mental disorder are common and highly disabled. Individual mental disorders have distinct patterns of psychiatric comorbidity and disability.

Senior Team Assessment and Referral Program--STAR

BACKGROUND

Although comprehensive geriatric assessment has been found to improve health and function and decrease hospital admissions, most such programs are staff-intensive and take many hours or even days. The Senior Team Assessment and Referral Program (STAR) was developed to address these two issues by using a short but comprehensive outpatient health appraisal that required only a few health professionals to complete.

METHODS

Six hundred forty-nine Kaiser Permanente health plan members aged 65 years or older who received their health care at the Kaiser Permanente Medical Center, San Jose, Calif, were randomly selected during the first 12 months of the study and invited by mail to participate in STAR. Of those members contacted, 326 agreed to join the study. A nurse practitioner evaluated the health, functional, and social status of each STAR participant at an office visit once each year for the next 3 years and provided case management for those participants found to be frail or in danger of becoming frail. A control group of 764 elderly (aged 65 years and older) Kaiser members with characteristics similar to those of the STAR participants was drawn from Kaiser Permanente health plan members in San Jose. They continued to receive usual medical care throughout the study. A medical-functional profile was developed to stratify each STAR participant's overall health and functional status at each visit and case management contact. The results were entered on a grid that was used as a tracking tool throughout the study. Utilization of medical services, changes in health and function, and effects of STAR interventions on participant health behaviors were measured, and primary care physician and participant satisfaction was assessed.

RESULTS

Although short-term utilization of medical services increased in the STAR group, health, function, and health behaviors improved as a result of STAR interventions. Ninety-three percent of the STAR participants described a satisfactory experience, and 71 percent were very satisfied. Sixty-five percent of primary care physicians who responded to a satisfaction questionnaire found something useful for their patients in the STAR assessment.

CONCLUSIONS

STAR offers an efficient, minimally staff-intensive model for evaluating the health, functional, and social status of the 65-year-old and older age-group and intervening when they are frail or at risk of becoming frail. The improved health, function, and healthy behaviors in STAR participants and the high satisfaction rates among participants and physicians suggest that STAR would be a useful addition to the health care environment.

The value of routine dilated pupil screening examination

We evaluated the cost-effectiveness of routine dilated fundus examination in improving visual outcomes. The cost of routine dilated fundus examination was related to the number of preventable cases of vision-threatening peripheral retinal disease. Patients with these diseases who had no risk factors were ascertained in a population of 1.75 million adults for a period of 6 months. Those whose last examination had been undilated were identified because only for them could routine dilated examination (RDE) have been substituted for undilated examination. The number of preventable cases was calculated for multiples of a 10% probability of prevention. The cost of RDE was determined from the number of undilated examinations in the same population and period and the cost of a single RDE. The number of patients who underwent undilated examination was estimated by random medical record review. The additional cost of a single RDE was determined from estimated examination times and payroll costs. Among patients without risk factors, 38 were identified for whom undilated examination rather than RDE had been performed. If prevention had been 10% effective, the substitution of 50,000 RDEs for undilated examinations costing the provider $433,000 would have been required per prevented case. These results suggest that most peripheral retinal diseases cannot be prevented by RDE. Routine dilated examination is an expensive test per prevented case. Published clinical guidelines lack evidence to recommend its use.

Safety and immunogenicity of Chiron/Biocine recombinant acellular pertussis-diphtheria-tetanus vaccine in infants and toddlers

OBJECTIVE

To evaluate the safety and immunogenicity of the recombinant acellular pertussis-diphtheria-tetanus (aPDT) vaccine (C-aPDT, Chiron/Biocine).

STUDY DESIGN

This is a randomized blinded trial evaluating the safety and immunogenicity of the recombinant aPDT vaccine (C-aPDT, Chiron/Biocine) in 2000 infant recipients compared with 498 controls who received whole cell diphtheria-pertussis-tetanus (wDPT; Connaught) vaccine at 2, 4 and 6 months of age. In addition the safety and immunogenicity of the same C-aPDT vaccine were evaluated as a booster dose in a subset of the same population when given at 15 to 18 months of age and compared with licensed Lederle aPDT vaccine.

RESULTS

The C-aPDT vaccine was associated with very few local or systemic reactions when compared with wDPT. In toddlers the local and systemic side effects observed were similar after either acellular vaccine. When the immunogenicity of the C-aPDT vaccine was compared with the wDPT (Connaught) in infancy, the vaccines were equivalent for anti-diphtheria response, the wDPT developed higher anti-tetanus response and the C-aPDT vaccine was significantly more immunogenic for all other antigens tested. In toddlers the C-aPDT acellular vaccine exhibited equal or improved immunogenicity for antigens tested as compared with Lederle aPDT except for a higher anti-filamentous hemagglutinin response with the Lederle aPDT vaccine.

CONCLUSION

The Chiron/Biocine aPDT vaccine offers an improved safety profile as well as improved immunogenicity when compared with a licensed wDPT product.

Identification of neonatal deaths in a large managed care organisation

The neonatal (< 28 days) mortality rate (NMR) is one of the most commonly employed maternal and child health epidemiological measures. It is also being employed in quality measures ("report cards') used to assess the performance of health care organisations. The objectives were to (1) develop methods for the rapid quantification of the neonatal mortality rate in a multi-hospital system, the Kaiser Permanente Medical Care Program's Northern California Region (KPMCP NCR), (2) develop methods for generating facility-specific rates and case lists, and (3) ascertain the capture rates of the information sources available to us. Potential neonatal deaths were identified in the KPMCP NCR for the 1990 and 1991 calendar years from 3 sources: (1) clerical searches of local facility records, (2) electronic searches of the KPMCP NCR hospitalisation database, and (3) linking KPMCP electronic birth records to death certificate tapes. The medical records of all infants identified through these methods were reviewed. The neonatal mortality rate was calculated in three ways: (1) including all livebirths, (2) excluding births weighing < 500 g, and (3) adjusting for prematurity by increasing the follow-up period in preterm babies (these babies were included as neonatal deaths if they died up to 40 weeks corrected age + 27.9 days). A total of 352 records out of 64 469 birth records in the KPMCP NCR were reviewed. If one includes babies < 500 g, the neonatal mortality rate was 3.72/1000 livebirths; if these babies are excluded, the rate was 3.05/1000. Adjusting for prematurity increased these rates to 3.91/1000 and 3.24/1000, respectively. Accurate quantification of the neonatal mortality rate in a multi-hospital system requires the use of multiple information sources. Use of a single source can lead to varying rates of over- or under-estimation. It is possible to employ our methodology for both research and operational purposes.

Variation in practice for discretionary admissions. Impact on estimates of quality of hospital care

OBJECTIVE

To demonstrate theoretically and empirically the existence of systematic bias in commonly reported standardized hospital mortality ratios when variation in hospital admission practice is not adjusted for in the analysis. The underlying analytic model used in hospital mortality analyses is specified and the confounding effect of selection bias arising from variation in admission practice is shown.

DATA SOURCES

An empirical example is presented using state-level data from the Health Care Financing Administration's Medicare Hospital Information Report for 1988 to 1990.

STUDY SELECTION

The Medicare Hospital Information data are used to demonstrate the effects of the bias because they contain population-based admission rates and mortality rates.

DATA SYNTHESIS

Selection bias arising from variation in admission practice causes the expected mortality rate to be overestimated for all hospitals, but especially for hospitals with more lenient admission practices. Using the Medicare Hospital Information Report, the resulting standardized hospital mortality ratios are shown to be significantly inversely correlated with higher relative risks of hospitalization (P < .01).

CONCLUSION

Standardized hospital mortality ratios based on analyses that do not account for variation in admission practice among hospitals are biased. Variation in admission practice will cause any outcome measure based solely on hospitalized patients to be similarly biased. Correction for selection bias is required to produce valid measures of hospital quality.

Safety of combined oligosaccharide conjugate Haemophilus influenzae type b (HbOC) and whole cell diphtheria-tetanus toxoids-pertussis vaccine in infancy. The Kaiser Permanente Pediatric Vaccine Study Group

The safety of the combined oligosaccharide conjugate Haemophilus influenzae (Hib) type b (HbOC) and whole cell diphtheria-tetanus toxoids-pertussis (DTP) vaccine (Tetramune, HbOC-DTP; Lederle) in infancy was evaluated in 6644 recipients of this vaccine and compared with 3914 recipients of separate injections of whole cell DTP and HbOC vaccines when given as a three dose regimen to infants at 2, 4 and 6 months of age in each group. Of the total number of infants in the study, a subset of 1435 were enrolled into the study and then randomly assigned to receive either the Hib-DPT combined vaccine or the separate components. This subset was used to assess local and systemic side effects which were evaluated utilizing telephone interviews 48 to 72 hours after vaccine. The remaining children in the study population were enrolled in a nonrandomized manner. For these children parents were offered the experimental Hib-DPT vaccine and refusers were given HbOC and DTP. Both of these groups of children as well as the randomized subset described above were used to assess rates of episodes of hospitalization, emergency room utilization and sudden infant death syndrome in HbOC-DTP recipients and children who received HbOC and DTP separately. Immunogenicity was evaluated in 123 children by collection of a single serum sample 30 days after the third dose of HbOC-DTP. The observed immunogenicity was comparable to that observed in other recent studies for HbOC and DTP component antigens. The profile of local and systemic side effects observed was virtually identical to that observed after DTP plus HbOC given separately.(ABSTRACT TRUNCATED AT 250 WORDS)

Safety, immunogenicity, and efficacy in infancy of oligosaccharide conjugate Haemophilus influenzae type b vaccine in a United States population: possible implications for optimal use

Between February 1988 and June 1990, the safety, immunogenicity, and efficacy of Haemophilus influenzae type b (Hib) oligosaccharide conjugate (HbOC) vaccine was evaluated in a prelicensure trial of 61,080 children. HbOC was found to be safe and immunogenic in infancy. Extended follow-up revealed that as of 31 December 1990, 30 cases of invasive Hib disease had occurred in 74,699 children; 26 were in unvaccinated children and 4 in children who had received only one dose. No disease occurred in children who had received two or three doses. By 30 September 1991, another case had occurred in an unvaccinated child. Comparison of these efficacy data with those of Hib capsular polysaccharide-outer membrane protein conjugate vaccine (PRP-OMP) reveals that both were effective in preventing disease in the first year of life. However, the small cohort in the PRP-OMP study did not allow demonstration of duration of protection beyond 1 year. Ongoing surveillance in larger populations is necessary to allow comparison of the duration of immunity provided by these vaccines.

Intense immunosuppression in chronic progressive multiple sclerosis: the Kaiser study

The value of a short course of intensive immunosuppression with cyclophosphamide in stabilising chronic progressive multiple sclerosis (MS) was examined in a randomised single-blinded, placebo-controlled clinical trial. Forty two patients, from the Kaiser Permanente Medical Care Program, Northern California, were studied. Twenty two patients received a short course of cyclophosphamide in an outpatient neurology clinic until their leucocyte counts fell below 4000/mm3, and 20 patients received folic acid. Level of disability, impairment of functional systems, and performance of social roles were assessed before randomisation and reassessed 12, 18, and 24 months after therapy. In both the cyclophosphamide and folic acid groups, the mean level of disability increased from the baseline examination to the 12 month follow up examination (the primary endpoint) by 0.5 on Kurtzke's Expanded Disability Status Scale, indicating similar disease progression in the two groups. Although immunosuppression therapy can be safely administered to MS patients in an outpatient clinic, evidence of substantial benefits was not found.

Efficacy in infancy of oligosaccharide conjugate Haemophilus influenzae type b (HbOC) vaccine in a United States population of 61,080 children. The Northern California Kaiser Permanente Vaccine Study Center Pediatrics Group

The efficacy of the HbOC conjugate Haemophilus influenzae type b vaccine was evaluated in a study population of 61,080 infants in the Northern California Kaiser Permanente Medical Care Program. Between February, 1988, and June, 1990, the HbOC vaccine was given as part of a three-dose series at 2, 4, and 6 months of age to 20,800 infants. The study population included children with a well-care visit at a study center during the first 6 months of life. There were 25 cases of Haemophilus influenzae type b disease in the study population: 22 in unvaccinated children and 3 in children who received only one dose of HbOC vaccine. The efficacy of the full three-dose series was evaluated by several methods: a primary analysis comparing fully vaccinated children with unvaccinated children from 7 to 18 months of age; a stratified exact analysis adjusted for age and seasonality; and a case-control analysis which further adjusted for known risk factors. The efficacy of three doses of vaccine was 100% with the lower bound of the 95% confidence interval for the three analyses at 68, 71, and 64%, respectively. There were no cases of disease resulting from two doses of HbOC vaccine yielding an estimate of 100% efficacy (95% confidence interval, 47 to 100) for two doses of HbOC vaccine. However, for children who had received only one dose of HbOC vaccine, vaccine efficacy was estimated to be 26% and the possibility that one dose of HbOC vaccine had no efficacy could not be excluded.(ABSTRACT TRUNCATED AT 250 WORDS)

Safety and immunogenicity of oligosaccharide conjugate Haemophilus influenzae type b (HbOC) vaccine in infancy. The Northern California Kaiser Permanente Vaccine Study Center Pediatrics Group

The safety and immunogenicity of the HbOC conjugate vaccine have been evaluated in a study population of 61,080 children in the Kaiser Permanente Medical Care Program of Northern California. Half of the population served as controls. The vaccine was given as part of a three-dose regimen in the first year of life with the first dose given between 6 weeks and 6 months of age, a minimum interval of 1 month between doses and with the third dose given by 1 year of age. The vaccine was highly immunogenic with 97% of infants developing 1 microgram/ml or more of anti-polyribosyl phosphate antibody as measured by Farr assay 1 month after completion of the three-dose series and with 71% maintaining this concentration until a booster dose was given at approximately 18 months of age. There were three cases of Haemophilus influenzae type b disease after the first dose of vaccine and two of these children died. However, there was no statistically significant difference between either the incidence of H. influenzae type b disease or the mortality rate in infants after one dose of HbOC vaccine when compared with H. influenzae type b disease incidence and mortality in unvaccinated children of the same age. The rate of sudden infant death syndrome following HbOC vaccine was lower than that observed within the Kaiser Permanente Medical Care Program as a whole or in the three counties in which sudden infant death syndrome surveillance was tabulated. Immediate local and systemic reactions were evaluated by telephone interviews of 6887 infants within 72 hours of vaccine.(ABSTRACT TRUNCATED AT 250 WORDS)

A survival analysis of hospitalization among patients with acquired immunodeficiency syndrome

Survival analysis techniques were used in estimating lifetime inpatient utilization among patients diagnosed with acquired immunodeficiency syndrome (AIDS) using data on 863 members of the Kaiser Permanente Medical Care Program in the Northern California Region diagnosed with AIDS between January 1, 1981 and June 30, 1987. Using information on both deceased and living patients, we estimated means of 40.3 lifetime inpatient days and 3.3 hospitalizations among all AIDS patients. Those presenting with Kaposi's sarcoma experienced a mean of 7.6 fewer lifetime inpatient days than those presenting with Pneumocystis carinii pneumonia (95% confidence interval = .61, 14.6) and a mean of 11.0 (3.9, 18.6) fewer inpatient days than all other AIDS patients. Older patients had fewer hospital admissions than younger ones. Year of diagnosis does not appear to be related to lifetime utilization, and there is an indication that increased survival has been accompanied by decreased inpatient utilization intensity as measured on a per person-year basis. We recommend the use of survival analysis methods in the study of utilization among groups of patients with incomplete follow-up.

Prognosis of gallstones with mild or no symptoms: 25 years of follow-up in a health maintenance organization

Two-hundred ninety-eight patients with gallstones accompanied by mild or nonspecific symptoms, 123 with asymptomatic gallstones, and 46 with nonfunction on cholecystogram and mild or nonspecific symptoms were followed in the setting of a health maintenance organization for up to 25 years after diagnosis. In a life-table analysis, complications (severe events) developed in about 1% per year of patients with visualized gallstones and in about 2% per year of patients with nonfunction. During each of the first 5 years after diagnosis, all events, both severe and non-severe (including surgery for continuing mild symptoms) occurred in about 6% of the patients with mild symptoms accompanying either gallstones or nonfunction, and in about 4% of patients with asymptomatic gallstones. The annual probabilities for all events tended to decrease as length of follow-up increased. Among patients with stones and mild symptoms, women were more apt to develop any event than men (p = 0.02) and more obese patients were more likely to develop severe events than those who were thinner (p = 0.05). The patients in this study are probably more representative of outpatients with gallstones seen by most primary care physicians than are most groups investigated previously for prognosis. Their event rates are sufficiently similar to those used in published decision analyses, that they should not alter previous conclusions that early elective cholecystectomy will have little positive or negative effect on average life expectancy of patients with gallstones.

The possible effect of increased surveillance on the incidence of malignant melanoma

We investigated the hypothesis that the increased incidence of malignant melanoma at the Lawrence Livermore National Laboratory (LLNL) in California was associated with a difference in medical care received by its employees compared with that received by other residents of the same geographic area. From records of the Kaiser Permanente Medical Care Program, to which about half of the LLNL employees belonged, we confirmed that the incidence of melanoma at the laboratory was 3.2 times that among members served by the Kaiser Permanente medical center in Walnut Creek, a nearby community (95% CI, 1.7-6.0). Rates of biopsy showing junctional, compound, and dermal nevi in men were also higher in the LLNL employees than in the other health-plan members (relative risks, 3.2, 2.4, and 1.3, respectively). When LLNL employees without melanoma were compared with community controls, we found that the employees had substantially more skin biopsies. Although the excess number of skin biopsies existed among LLNL employees before publicity about the problem, this excess increased after the publicity. Exposure to some environmental agent(s) or personal risk factors may have caused clinically suspicious pigmented lesions that required LLNL employees to have more skin biopsies. On the other hand, awareness of the laboratory's excess melanoma incidence may have increased physicians' propensity to obtain biopsy specimens of pigmented lesions.