Refilling and switching of antiepileptic drugs and seizure-related events

We sought to estimate the risk of seizure-related events associated with refilling prescriptions for antiepileptic drugs (AEDs) and to estimate the effect of switching between brand-name and generic drugs or between two generic versions of the same drug. We conducted a case-crossover study using health-care databases from British Columbia, Canada, among AED users who had an emergency room visit or hospitalization for seizure (index seizure-related event), defined using International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9) codes 345.xx (epilepsy and recurrent seizures) and 780.3x (convulsions), between 1997 and 2005. AED prescription refilling itself was associated with 2.3-fold elevated odds of seizure-related events when the refill occurred within 21 days before the index event (odds ratio (OR) 2.31; 95% confidence interval (CI) 1.56-3.44). The OR was 2.75 (95% CI 0.88-8.64) for refills that involved switching, yielding a refill-adjusted OR for switching of 1.19 (95% CI 0.35-3.99). Refilling the same AED prescription was associated with an elevated risk of seizure-related events whether or not the refill involved switching from a brand-name to a generic product.

Infliximab and other immunomodulating drugs in patients with inflammatory bowel disease and the risk of serious bacterial infections

BACKGROUND

There remain concerns about the safety of infliximab therapy in patients with inflammatory bowel disease (IBD).

AIM

To assess the association between the initiation of infliximab and other immunomodulating drugs and the risk of serious bacterial infection in the treatment of IBD.

METHODS

We assembled a cohort study of patients with IBD, including Crohn's disease (CD) and ulcerative colitis (UC). All patients initiating an immunomodulating drug between January 2001 and April 2006 were identified in British Columbia from linked health care utilization databases. Exposure of interest was initiation of infliximab or corticosteroids compared with initiation of other immunosuppressive agents, including azathioprine, mercaptopurine (MP) and methotrexate (MTX). Outcome of interest was serious bacterial infections requiring hospitalization, including Clostridium difficile.

RESULTS

Among 10 662 IBD patients, the incidence rate of bacteriaemia ranged from 3.8 per 1000 person-years (95% confidence interval 2.1-6.2) for other immunosuppressive agents to 7.4 (3.3-19.3) for infliximab with slightly higher rate for serious bacterial infections resulting in an adjusted relative risk 1.4 (0.47-4.24). Clostridium difficile infections occurred in 0/1000 (0-5.4) among 521 infliximab initiations and 14/1000 (10.6-18.2) for corticosteroids. Corticosteroid initiation tripled the risk of C. difficile infections (RR = 3.4; 1.9-6.1) compared with other immunosuppressant agents. This corticosteroid effect was neither dose-dependent nor duration-dependent. Bacteriaemia and other serious bacterial infections were not increased by corticosteroids or infliximab (5 events).

CONCLUSIONS

In a population-based cohort of patients with IBD, we found no meaningful association between infliximab and serious bacterial infections, although some subgroups had few events. Corticosteroid initiation increased the risk for C. difficile infections in these patients.

The relation between bisphosphonate use and non-union of fractures of the humerus in older adults

SUMMARY

While nitrogen-containing bisphosphonates have been shown to reduce fracture risk in postmenopausal women and men, their safety in the period after a fracture is unclear. In fully adjusted multivariable regression models, bisphosphonate use in the post-fracture period was associated with an increased probability of non-union [odds ratio (OR) 2.37, 95% confidence interval (CI) 1.13-4.96]. Clinicians might consider waiting for several months before introduction of a bisphosphonate after a fracture.

INTRODUCTION

While nitrogen-containing bisphosphonates have been shown to reduce fracture risk in postmenopausal women and men, their safety in the period after a fracture is unclear. We examined the risk of non-union associated with post-fracture bisphosphonate use among a group of older adults who had experienced a humerus fracture.

METHODS

We conducted a nested case-control study among subjects who had experienced a humerus fracture. From this cohort, cases of non-union were defined as those with an orthopedic procedure related to non-union 91-365 days after the initial humerus fracture. Bisphosphonate exposure was assessed during the 365 days prior to the non-union among cases or the matched date for controls. Multivariable logistic regression models were examined to calculate the OR and 95% CI for the association of post-fracture bisphosphonate use with non-union.

RESULTS

From the cohort of 19,731 patients with humerus fractures, 81 (0.4%) experienced a non-union. Among the 81 cases, 13 (16.0%) were exposed to bisphosphonates post-fracture, while 69 of the 810 controls (8.5%) were exposed in the post-fracture interval. In fully adjusted multivariable regression models, bisphosphonate use in the post-fracture period was associated with an increased odds of non-union (OR 2.37, 95% CI 1.13-4.96). Albeit limited by small sample sizes, the increased risk associated with bisphosphonate use persisted in the subgroup of patients without a history of osteoporosis or prior fractures (OR 1.91, 95% CI 0.75-4.83).

CONCLUSIONS

In this study of older adults, non-union after a humerus fracture was rare. Bisphosphonate use after the fracture was associated with an approximate doubling of the risk of non-union.

Developments in post-marketing comparative effectiveness research

Physicians and insurers need to weigh the effectiveness of new drugs against existing therapeutics in routine care to make decisions about treatment and formularies. Because Food and Drug Administration (FDA) approval of most new drugs requires demonstrating efficacy and safety against placebo, there is limited interest by manufacturers in conducting such head-to-head trials. Comparative effectiveness research seeks to provide head-to-head comparisons of treatment outcomes in routine care. Health-care utilization databases record drug use and selected health outcomes for large populations in a timely way and reflect routine care, and therefore may be the preferred data source for comparative effectiveness research. Confounding caused by selective prescribing based on indication, severity, and prognosis threatens the validity of non-randomized database studies that often have limited details on clinical information. Several recent developments may bring the field closer to acceptable validity, including approaches that exploit the concepts of proxy variables using high-dimensional propensity scores, within-patient variation of drug exposure using crossover designs, and between-provider variation in prescribing preference using instrumental variable (IV) analyses.

Patterns of cardiovascular risk in rheumatoid arthritis

BACKGROUND

Although it is known that rheumatoid arthritis is associated with an increased risk of cardiovascular disease (CVD), the pattern of this risk is not clear. This study investigated the relative risk of myocardial infarction, stroke and CVD mortality in adults with rheumatoid arthritis compared with adults without rheumatoid arthritis across age groups, sex and prior CVD event status.

METHODS

We conducted a cohort study among all residents aged >or=18 years residing in British Columbia between 1999 and 2003. Residents who had visited the doctor at least thrice for rheumatoid arthritis (International Classification of Disease = 714) were considered to have rheumatoid arthritis. A non-rheumatoid arthritis cohort was matched to the rheumatoid arthritis cohort by age, sex and start of follow-up. The primary composite end point was a hospital admission for myocardial infarction, stroke or CVD mortality.

RESULTS

25 385 adults who had at least three diagnoses for rheumatoid arthritis during the study period were identified. During the 5-year study period, 375 patients with rheumatoid arthritis had a hospital admission for myocardial infarction, 363 had a hospitalisation for stroke, 437 died from cardiovascular causes and 1042 had one of these outcomes. The rate ratio for a CVD event in patients with rheumatoid arthritis was 1.6 (95% confidence interval (CI) 1.5 to 1.7), and the rate difference was 5.7 (95% CI 4.9 to 6.4) per 1000 person-years. The rate ratio decreased with age, from 3.3 in patients aged 18-39 years to 1.6 in those aged >or=75 years. However, the rate difference was 1.2 per 1000 person-years in the youngest age group and increased to 19.7 per 1000 person-years in those aged >or=75 years. Among patients with a prior CVD event, the rate ratios and rate differences were not increased in rheumatoid arthritis.

CONCLUSIONS

This study confirms that rheumatoid arthritis is a risk factor for CVD events and shows that the rate ratio for CVD events among subjects with rheumatoid arthritis is highest in young adults and those without known prior CVD events. However, in absolute terms, the difference in event rates is highest in older adults.

Incidence and predictors for chronicity of headache in patients with episodic migraine

The authors followed 532 consecutive patients with episodic migraine (<15 days/month) for 1 year. Sixty-four patients (14%) developed chronic headache (>/=15 days/month). The odds ratios for developing CH were 20.1 (95% CI 5.7 to 71.5) comparing patients with a "critical" (10 to 14 days/month) vs "low" (0 to 4 days/month) and 6.2 (95% CI 1.7 to 26.6) in patients with an "intermediate" (6 to 9 days/month) vs "low" headache frequency and 19.4 (95% CI 8.7 to 43.2) comparing patients with and without medication overuse.

Case-crossover and case-time-control designs as alternatives in pharmacoepidemiologic research

Standard cohort and case-control designs are suited to the study of cumulative effects of chronic exposures, but they are prone to confounding by indication. Case-crossover and case-time-control studies are especially useful for studying intermittent exposures with transient effects, and are less susceptible to confounding by indication. Each design has its strengths and weaknesses. Despite the increasing availability of automated databases, cohort studies are usually time consuming and expensive, and therefore not preferred for time-critical decisions. In case-control studies, the selection of appropriate controls can be difficult and time consuming, and sometimes impractical when the exposure is rare. Case-crossover studies use the exposure history of each case as his or her own control to examine the effect of transient exposures on acute events. It further allows to study the time relationship of immediate effects to the exposure. This design eliminates between-person confounding by constant characteristics, including chronic indications. Because exposure data for the case and control periods are provided by the same person, the problems of differential recall may be reduced in many but not all case-crossover studies. Bias can result from temporal changes in prescribing or within-person confounding, including transient indication or changes in disease severity. The case-time-control design is an elaboration of the case-crossover design, which uses exposure history data from a traditional control group to estimate and adjust for the bias from temporal changes in prescribing. This paper will present a structured decision table of when to use which design in pharmacoepidemiologic research. In conclusion, case-crossover and case-time-control studies are the designs of choice when separating acute effects from chronic effects of transient exposures and if confounding by indication is an outstanding problem.

Adverse drug reaction monitoring--cost and benefit considerations. Part I: frequency of adverse drug reactions causing hospital admissions

In an era of health care cost containment it is of particular interest to identify measures that reduce costs and at the same time improve health care quality. One of these cost cutting measures might be the reduction of the frequency of Adverse Drug Reactions (ADR). The objective of this paper is to summarize all original work on ADR frequencies at hospital admission and to come up with a valid estimate for the actual frequency of ADR-related hospital admissions. Additionally, we compared established concepts of ADR monitoring with respect to their utility for drug safety monitoring and pharmacoepidemiologic research. We reviewed 25 studies from the past 25 years. Analysing the effect of methodological characteristics showed that variation of reported ADR frequency mainly depends on differing study bases and the concepts of ADR monitoring. Investigations that thoroughly screened all members of the study population for the presence of adverse drug reactions (comprehensive ADR monitoring) generally yielded highest ADR proportions. Studies that concentrated screening on selected high-risk patients (preselective ADR monitoring) and those applying spontaneous or intensified spontaneous reporting detected lower ADR proportions (2.9% and 2.5%). The ADR proportion among admissions to departments of internal medicine was higher than among mixed hospital populations including surgical patients. In conclusion 4.2-6.0% (lower and upper quartile) and in median 5.8% of all admissions to medical departments are caused by adverse drug reactions. A two-step preselective ADR monitoring appears to be appropriate and efficient for both signal generation and signal validation as compared to spontaneous reporting and comprehensive monitoring. In conclusion, adverse drug reactions are a common cause of hospital admissions. As hospital care is expensive, attempts to prevent ADR and thus hospital admission need active encouragement.

Adverse drug reaction monitoring--cost and benefit considerations. Part I: frequency of adverse drug reactions causing hospital admissions

In an era of health care cost containment it is of particular interest to identify measures that reduce costs and at the same time improve health care quality. One of these cost cutting measures might be the reduction of the frequency of Adverse Drug Reactions (ADR). The objective of this paper is to summarize all original work on ADR frequencies at hospital admission and to come up with a valid estimate for the actual frequency of ADR-related hospital admissions. Additionally, we compared established concepts of ADR monitoring with respect to their utility for drug safety monitoring and pharmacoepidemiologic research. We reviewed 25 studies from the past 25 years. Analysing the effect of methodological characteristics showed that variation of reported ADR frequency mainly depends on differing study bases and the concepts of ADR monitoring. Investigations that thoroughly screened all members of the study population for the presence of adverse drug reactions (comprehensive ADR monitoring) generally yielded highest ADR proportions. Studies that concentrated screening on selected high-risk patients (preselective ADR monitoring) and those applying spontaneous or intensified spontaneous reporting detected lower ADR proportions (2.9% and 2.5%). The ADR proportion among admissions to departments of internal medicine was higher than among mixed hospital populations including surgical patients. In conclusion 4.2-6.0% (lower and upper quartile) and in median 5.8% of all admissions to medical departments are caused by adverse drug reactions. A two-step preselective ADR monitoring appears to be appropriate and efficient for both signal generation and signal validation as compared to spontaneous reporting and comprehensive monitoring. In conclusion, adverse drug reactions are a common cause of hospital admissions. As hospital care is expensive, attempts to prevent ADR and thus hospital admission need active encouragement.

Frequency and predictors of drug therapy interruptions after hospital discharge under physician drug budgets in Germany

OBJECTIVE

We sought to study how frequently prescription drug therapy at hospital discharge was discontinued or changed by general practitioners under physician drug budgets in Germany and explore reasons and predictors for such discontinuations.

METHODS

This cohort study was part of a larger project on clinical outcomes of acute hospital care in patients with 5 groups of medical diagnoses, including conditions of the heart, lung and brain, gastroduodenal ulcer disease and diabetes. Patients entered the study cohort at hospital admission and were followed throughout their stay until they had their first encounter with a primary care physician responsible for follow-up treatment after hospital discharge. Nurse practitioners and physicians assessed patient characteristics at admission and discharge. A 1-page questionnaire on continuity of care, including drug therapy, was provided to primary care physicians at the first patient encounter. The primary study endpoint was discontinuation of drug therapy by the primary care physician. Data were analyzed by multivariate logistic regression.

RESULTS

A total of 3,267 patients in 22 primary care hospitals were eligible for the study. Standardized questionnaires on continuation of drug therapy were returned by 890 patients (27%); 846 patients (95%) used prescription drugs at discharge. Of those, drug therapy was interrupted in 122 (14%). Reasons for discontinuations included excessive costs of drugs in 66 patients (54%), excessive number of drugs prescribed (32, 26%) and differences in judgment on the clinical appropriateness of a drug (23, 19%). In a multivariate logistic regression, gastroduodenal ulcer disease was a significant predictor for discontinuation (OR = 3.1; 95% CI 1.5 - 6.5). Discontinuation tended to be more likely in older patients (69 - 76 years vs. < or = 58: OR = 2.0; 1.0 - 3.9) but slightly less likely in male patients (OR = 0.7; 0.4 - 1.1).

CONCLUSION

Discontinuation of drug therapy after hospital discharge is common. The high costs of prescription drugs were the most common reason. Elderly patients seem to be particularly affected.

Performance of comorbidity scores to control for confounding in epidemiologic studies using claims data

Comorbidity is an important confounder in epidemiologic studies. The authors compared the predictive performance of comorbidity scores for use in epidemiologic research with administrative databases. Study participants were British Columbia, Canada, residents aged >or=65 years who received angiotensin-converting enzyme inhibitors or calcium channel blockers at least once during the observation period. Six scores were computed for all 141,161 participants during the baseline year (1995-1996). Endpoints were death and health care utilization during a 12-month follow-up (1996-1997). Performance was measured by using the c statistic ranging from 0.5 for chance prediction of outcome to 1.0 for perfect prediction. In logistic regression models controlling for age and gender, four scores based on the International Classification of Diseases, Ninth Revision (ICD-9) generally performed better at predicting 1-year mortality (c = 0.771, c = 0.768, c = 0.745, c = 0.745) than medication-based Chronic Disease Score (CDS)-1 and CDS-2 (c = 0.738, c = 0.718). Number of distinct medications used was the best predictor of future physician visits (R(2) = 0.121) and expenditures (R(2) = 0.128) and a good predictor of mortality (c = 0.745). Combining ICD-9 and medication-based scores improved the c statistics (1.7% and 6.2%, respectively) for predicting mortality. Generalizability of results may be limited to an elderly, predominantly White population with equal access to state-funded health care.

A case-control study of the effect of infant feeding on celiac disease

AIMS

The aim of this study was to investigate the association between the duration of breast-feeding and the age at the first gluten introduction into the infant diet and the incidence and age at onset of celiac disease.

METHODS

In a case-control study, 143 children with celiac disease and 137 randomly recruited gender- and age-matched control children were administered a standardized questionnaire. Multivariate-adjusted odds ratios (OR) as estimates of the relative risk and corresponding 95% confidence intervals (95% CI) were calculated.

RESULTS

The risk of developing celiac disease decreased significantly by 63% for children breast-fed for more than 2 months (OR 0.37, 95% CI 0.21-0.64) as compared with children breast-fed for 2 months or less. The age at first gluten introduction had no significant influence on the incidence of celiac disease (OR 0.72, 95% CI 0.29-1.79 comparing first gluten introduction into infant diet >3 months vs. < or =3 months).

CONCLUSIONS

A significant protective effect on the incidence of celiac disease was suggested by the duration of breast-feeding (partial breast-feeding as well as exclusive breast-feeding). The data did not support an influence of the age at first dietary gluten exposure on the incidence of celiac disease. However, the age at first gluten exposure appeared to affect the age at onset of symptoms.

First results from an intensified monitoring system to estimate drug related hospital admissions

AIMS

An intensified monitoring system was set up to identify drug related hospital admissions and estimate population-based incidences for commonly prescribed medications.

METHODS

Pharmacovigilance-centres systematically screened nonelective admissions to emergency rooms or departments of internal medicine for drug related hospitalizations (DRH). Clinical pharmacologists used standardized causality assessment. Service areas of each acute care hospital were defined by 5 digit postal codes that covered 60% of all admissions. Drug dispensing information was available through claims processed by regional pharmacy computing centres. Quarterly incidences were estimated by dividing the number of events by the number of treated patients.

RESULTS

435 DRHs were reported during five quarters. The incidence of ADRs leading to admissions varied for specific drug groups from 1.5/10 000 treated patients to 24/10 000. Quarterly variation of incidences was moderate except for insulin and calcium antagonists. 95% confidence intervals overlap for all quarters within each group. Incidences are sensitive to changes in the definition of the source population.

CONCLUSIONS

Our pharmacovigilance monitoring system allows comparisons of population-based incidences of drug-related hospitalizations among drugs and over time. It provides important information for risk management and monitoring outcomes of pharmaceutical quality management programmes.

Patientenzentrierte Evaluation des Gesundheitszustands in einem longitudinalen Qualitätsmanagementsystem im Krankenhaus (QMK)

OBJECTIVE

The objective was to assess the value of self-reported health status as an indicator of outcomes of acute hospital care, to identify potential practical limitations, and develop strategies for future applications.

METHODS

180 patients from 4 acute care hospitals in Germany participated in a comprehensive and longitudinal assessment of outcome of care in general internal medicine between 8/1/99 and 10/31/99. Self-administered SF-36 surveys were completed at admission and 4 weeks after discharge. Additionally, nurses and physicians answered questions regarding the patients' health status. Linear relations between health status assessments were quantified as correlation coefficients. Odds ratios (OR) and 95% confidence limits from multivariate logistic regression models were reported for predictors of non-returned questionnaires.

RESULTS

33% of SF-36 surveys handed out at discharge were returned. Patients with impairments and referred patients were more likely not to return the survey (OR = 1.3 [1.09; 1.66] and OR = 3.7 [1.37; 9.87]). The linear relation of SF-36 and SF-12 scores in the same patients were r = 0.95 [0.91; 0.97] for physical health and r = 0.91 [0.85; 0.94] for mental health. Physicians and nurses moderately agreed in their assessment of patients' health (r = 0.38 [0.22; 0.52]) but both professional groups showed poor agreement with self-reported health (r = 0.15 [-0.08; 0.36] and r = -0.01 [-0.23; 0.21]).

CONCLUSIONS

1. Self-reported health status should be considered in the assessment of outcomes of acute care as a dimension that is to some extent independent of health status assessment by professionals, 2. shorter instruments, i.e., the SF-12, can be used instead of the SF-36, 3. a self-reported health status assessment is feasible 4 weeks after discharge, and 4. patients with multiple impairments or those who are transferred should get specific support in the completion of questionnaires to increase response or to receive at least minimal information about their health status.

Sensitivity analysis of the diagnostic value of endoscopies in cross-sectional studies in the absence of a gold standard

OBJECTIVES

The evaluation of the diagnostic value of endoscopic procedures usually lacks a gold standard when performed in cross-sectional studies. The objective is to demonstrate an easily applicable method to assess the possible range of sensitivity, specificity, and predictive values of endoscopic procedures in the absence of a gold standard method.

METHODS

Data from a study of 328 endoscopies comparing two different methods to diagnose superficial bladder cancer were used as a numerical example. Both endoscopic procedures were performed in the same patients in one session. Under the assumption of a systematic misclassification process, a model to correct sensitivity estimates is developed.

RESULTS

The lowest possible sensitivity estimate for a new fluorescence endoscopy technique (FE) was 78%, the maximum 97.5%. Depending on realistic assumptions made upon the misclassification, a reasonable estimate for sensitivity was 93.4% (95% confidence interval [CI]: 90%-97.3%) for the FE technique. The sensitivity of the traditional white-light endoscopy method ranged from 47.2% to 53%, with a reasonable estimate of 46.7% (95% CI: 39.4%-54.3%).

CONCLUSIONS

This method to determine the theoretically possible range of sensitivity estimates in endoscopic procedures is helpful in cross-sectional studies with a missing gold standard method. It is easily applicable for a variety of endoscopic procedures, including upper and lower gastro-intestinal tract, urogenital tract, or diagnostic laparoscopic surgery.

On the evaluation of drug benefits policy changes with longitudinal claims data: the policy maker's versus the clinician's perspective

Cost containment in pharmaceutical-benefit plans are often controversially debated for their potential of unintended consequences on health and overall expenditures. Thorough evaluations are needed but hypotheses and design considerations are complex. Our objective is to provide a structured framework for the evaluation of drug-benefit changes using longitudinal claims data. Differential cost sharing (DCS) will serve as a recent example. Benefit-plan managers are mainly interested in the overall performance of their plan. In a policy model, any observed policy-related effects may be compared with what would have happened had the intervention not been implemented by extrapolating the pre-policy trend from the same patients. These estimates will reflect the global consequences of the policy maker's decision. However, such estimates represent summary effects of benefits and harms, separately identifiable in those complying with the intended policy and those not complying. Results from a policy model apply only to a specific policy implementation and tend to underestimate effects when non-compliance is high. Clinical-decision makers and patients, by contrast, are interested in the consequences of patients' actual compliance to the policy. A clinical model assesses the effects of DCS depending on the actual treatment in contrast to the treatment intended by the policy. However, this model must sometimes make, unprovable assumptions about the appropriate control of selection factors. In conclusion, both policy and clinical models should be tested with a clear understanding of their perspectives, hypotheses, and interpretations, using quasi-experimental time-series designs to evaluate the effects of drug cost-containment policies.

[An update of the German version of AEP (Appropriateness Evaluation Protocol): metric properties and practical experiences]

The development of a German version of the Appropriateness Evaluation Protocol (AEP) allows for the first time the evaluation of hospital admissions and bed days in Germany. The instrument is based on international experience and has been adopted in cooperation with acknowledged members of German surgical and medical societies. The AEP showed excellent reliability in general internal medicine as well as in surgery. The validity is comparable to international studies, although further research is necessary. Approximately 90% of surgical cases could be evaluated according to the criteria of the AEP; the remaining patients were evaluated using the "override option". The majority of inappropriate care is due to poor documentation in medical records and management deficiencies during inpatient care.