Real-World Tumor Response of Palbociclib in Combination With an Aromatase Inhibitor as First-Line Therapy in Pre/Perimenopausal Women With Metastatic Breast Cancer.

BACKGROUND: Limited real-world data exist regarding the efficacy of palbociclib in combination with endocrine therapy in pre/perimenopausal women with metastatic breast cancer. OBJECTIVE: We aimed to compare real-world tumor responses among pre/perimenopausal women who initiated palbociclib plus an aromatase inhibitor (AI) or AI monotherapy as first-line treatment for hormone receptor-positive/human epidermal growth factor receptor 2-negative metastatic breast cancer. METHODS: This retrospective observational cohort study (NCT05012644) used electronic health record data from The US Oncology Network. Tumor responses were determined based on treating clinicians' assessments of radiologic evidence for changes in disease burden. Normalized inverse probability treatment weighting was used to balance baseline characteristics between treatment cohorts. RESULTS: Of 196 pre/perimenopausal women, 116 and 80 were in the palbociclib plus AI cohort and AI cohort, respectively. Real-world response rates (complete or partial response) were 52.1% and 46.2%, respectively (odds ratio, 1.27 [95% confidence interval 0.72‒2.24]). Among patients with one or more tumor assessments on treatment, real-world response rates were 60.0% in the palbociclib plus AI cohort (n = 103) and 49.9% in the AI cohort (n = 71; odds ratio, 1.51 [95% confidence interval 0.82‒2.77]). CONCLUSIONS: This real-world analysis suggests that pre/perimenopausal patients with hormone receptor-positive/human epidermal growth factor receptor 2-negative metastatic breast cancer appear more likely to respond to palbociclib plus AI versus AI alone as first-line therapy, which may support the combination as a standard-of-care treatment for this patient population.

Palbociclib (Ibrance^®) is a medicine for patients with metastatic breast cancer (MBC). Metastatic means that the cancer has spread to other places in the body. Patients take palbociclib with hormone therapy, such as an aromatase inhibitor (AI). Palbociclib plus an AI is a treatment for a type of MBC called HR+/HER2‒ MBC. HR+/HER2‒ stands for hormone receptor positive, human epidermal growth factor receptor 2 negative. Researchers wanted to observe responses to treatment in routine clinical practice among women with HR+/HER2­ MBC who had not reached menopause. A response is if a tumor shrinks or disappears after treatment. This study used healthcare information reported in electronic medical records of patients seen by doctors in The US Oncology Network. This study included 196 women with HR+/HER2­ MBC who had not reached menopause and had not received prior treatment for MBC. A total of 116 women received palbociclib plus an AI, and 80 women received an AI alone. Researchers used standard statistical approaches to balance baseline characteristics between the two treatment groups. These adjustments made the groups more similar so that researchers could compare treatment responses. Sixty percent of patients who took palbociclib plus an AI responded, compared with 50% of patients who took an AI alone. These results suggest that palbociclib plus an AI may benefit women with HR+/HER2‒ MBC who have not reached menopause.

COVID-19 Evidence Accelerator: A parallel analysis to describe the use of Hydroxychloroquine with or without Azithromycin among hospitalized COVID-19 patients.

BACKGROUND: The COVID-19 pandemic remains a significant global threat. However, despite urgent need, there remains uncertainty surrounding best practices for pharmaceutical interventions to treat COVID-19. In particular, conflicting evidence has emerged surrounding the use of hydroxychloroquine and azithromycin, alone or in combination, for COVID-19. The COVID-19 Evidence Accelerator convened by the Reagan-Udall Foundation for the FDA, in collaboration with Friends of Cancer Research, assembled experts from the health systems research, regulatory science, data science, and epidemiology to participate in a large parallel analysis of different data sets to further explore the effectiveness of these treatments. METHODS: Electronic health record (EHR) and claims data were extracted from seven separate databases. Parallel analyses were undertaken on data extracted from each source. Each analysis examined time to mortality in hospitalized patients treated with hydroxychloroquine, azithromycin, and the two in combination as compared to patients not treated with either drug. Cox proportional hazards models were used, and propensity score methods were undertaken to adjust for confounding. Frequencies of adverse events in each treatment group were also examined. RESULTS: Neither hydroxychloroquine nor azithromycin, alone or in combination, were significantly associated with time to mortality among hospitalized COVID-19 patients. No treatment groups appeared to have an elevated risk of adverse events. CONCLUSION: Administration of hydroxychloroquine, azithromycin, and their combination appeared to have no effect on time to mortality in hospitalized COVID-19 patients. Continued research is needed to clarify best practices surrounding treatment of COVID-19.

Real-world evidence of bariatric surgery and cardiovascular benefits using electronic health records data: A lesson in bias.

AIM: To reproduce and correct studies on bariatric surgery and the reduction in major adverse cardiovascular events (MACE) among patients with obesity and type 2 diabetes (T2D). METHODS: We used electronic healthcare records (EHR) from in and outpatient facilities around the United States to identify a cohort of patients with T2D, aged 18 to 80 years and with a body mass index (BMI) of 30 kg/m2 or higher undergoing bariatric surgery. We compared against hip/knee arthroplasty to establish an active comparison group that reduced bias from differential information and confounding. The main outcome was six-point MACE. Pre-exposure characteristics were adjusted in propensity score (PS) models with 1:2 matching plus high-dimensional PS matching. RESULTS: After a range of exclusions, the final cohort included 344 bariatric surgery patients (65% female; mean age 58 years) and 551 PS-matched patients undergoing arthroplasty (65% female; 59 years). Median follow-up was 2.5 years in both groups. Bariatric surgery patients showed a sustained 20% weight reduction and an HbA1c reduction by 1% point. We found no benefits of bariatric surgery for six-point MACE (HR = 0.99; 95% CI 0.76-1.30). We observed known increases in risks for vitamin B12 deficiency anaemia (HR = 3.06; 1.10-8.49) and cholelithiasis (HR = 1.72; 0.94-3.13). CONCLUSIONS: This real-world evidence study found reductions in HbA1c and BMI following bariatric surgery similar to trials, and no meaningful cardiovascular benefit compatible with the underpowered trials but in contrast to earlier EHR studies. We showed how information bias typical in EHR analyses and confounding may cause substantial bias.

Empirical assessment of case-based methods for identification of drugs associated with upper gastrointestinal bleeding in the French National Healthcare System database (SNDS).

PURPOSE: Upper gastrointestinal bleeding (UGIB) is a severe and frequent drug-related event. In order to enable efficient drug safety alert generation in the French National Healthcare System database (SNDS), we assessed and calibrated empirically case-based designs to identify drug associated with UGIB risk. METHODS: All cases of UGIB were extracted from SNDS (2009-2014) using two definitions. Positive and negative drug controls were used to compare 196 self-controlled case series (SCCS), case-control (CC) and case-population (CP) design variants. Each variant was evaluated in a 1/10th population sample using area under the receiver operating curve (AUC) and mean square error (MSE). Parameters that had major impacts on results were identified through logistic regression. Optimal designs were replicated in the unsampled population. RESULTS: Using a specific UGIB definition, AUCs ranged from 0.64 to 0.80, 0.44 to 0.61 and 0.50 to 0.67, for SCCS, CC and CP, respectively. MSE ranged from 0.07 to 0.39, 0.83 to 1.33 and 1.96 to 4.6, respectively. Univariate regressions showed that high AUCs were achieved with SCCS with multiple drug adjustment and a 30-day risk window starting at exposure. The top-performing SCCS variant in the unsampled population yielded an AUC = 0.84 and MSE = 0.14, with 10/36 negative controls presenting significant estimates. CONCLUSIONS: SCCS adjusting for multiple drugs and using a 30-day risk window has the potential to generate UGIB-related alerts in the SNDS and hypotheses on its potential population impact. Negative control implementation highlighted that low systematic error was generated but that protopathic bias and confounding by indication remained unaddressed issues.

Empirical assessment of case-based methods for drug safety alert identification in the French National Healthcare System database (SNDS): Methodology of the ALCAPONE project.

OBJECTIVES: To introduce the methodology of the ALCAPONE project. BACKGROUND: The French National Healthcare System Database (SNDS), covering 99% of the French population, provides a potentially valuable opportunity for drug safety alert generation. ALCAPONE aimed to assess empirically in the SNDS case-based designs for alert generation related to four health outcomes of interest. METHODS: ALCAPONE used a reference set adapted from observational medical outcomes partnership (OMOP) and Exploring and Understanding Adverse Drug Reactions (EU-ADR) project, with four outcomes-acute liver injury (ALI), myocardial infarction (MI), acute kidney injury (AKI), and upper gastrointestinal bleeding (UGIB)-and positive and negative drug controls. ALCAPONE consisted of four main phases: (1) data preparation to fit the OMOP Common Data Model and select the drug controls; (2) detection of the selected controls via three case-based designs: case-population, case-control, and self-controlled case series, including design variants (varying risk window, adjustment strategy, etc.); (3) comparison of design variant performance (area under the ROC curve, mean square error, etc.); and (4) selection of the optimal design variants and their calibration for each outcome. RESULTS: Over 2009-2014, 5225 cases of ALI, 354 109 MI, 12 633 AKI, and 156 057 UGIB were identified using specific definitions. The number of detectable drugs ranged from 61 for MI to 25 for ALI. Design variants generated more than 50 000 points estimates. Results by outcome will be published in forthcoming papers. CONCLUSIONS: ALCAPONE has shown the interest of the empirical assessment of pharmacoepidemiological approaches for drug safety alert generation and may encourage other researchers to do the same in other databases.

Measuring prevalence and incidence of chronic conditions in claims and electronic health record databases.

BACKGROUND: Health care databases are natural sources for estimating prevalence and incidence of chronic conditions, but substantial variation in estimates limits their interpretability and utility. We evaluated the effects of design choices when estimating prevalence and incidence in claims and electronic health record databases. METHODS: Prevalence and incidence for five chronic diseases at increasing levels of expected frequencies, from cystic fibrosis to COPD, were estimated in the Clinical Practice Research Datalink (CPRD) and MarketScan databases from 2011 to 2014. Estimates were compared using different definitions of lookback time and contributed person-time. RESULTS: Variation in lookback time substantially affected estimates. In 2014, for CPRD, use of an all-time vs a 1-year lookback window resulted in 4.3-8.3 times higher prevalence (depending on disease), reducing incidence by 1.9-3.3 times. All-time lookback resulted in strong temporal trends. COPD prevalence between 2011 and 2014 in MarketScan increased by 25% with an all-time lookback but stayed relatively constant with a 1-year lookback. Varying observability did not substantially affect estimates. CONCLUSION: This framework draws attention to the underrecognized potential for widely varying incidence and prevalence estimates, with implications for care planning and drug development. Though prevalence and incidence are seemingly straightforward concepts, careful consideration of methodology is required to obtain meaningful estimates from health care databases.

Selective Serotonin Reuptake Inhibitor Use and Perioperative Bleeding and Mortality in Patients Undergoing Coronary Artery Bypass Grafting: A Cohort Study.

INTRODUCTION: Several small studies have reported inconsistent findings about the safety of selective serotonin reuptake inhibitors (SSRIs) among patients undergoing coronary artery bypass grafting (CABG). We sought to investigate post-CABG bleeding and mortality outcomes related to antidepressant exposure. METHODS: We identified patients who underwent CABG between 2004 and 2008 in the Premier Perspective Comparative Database. We determined whether they received SSRIs, other antidepressants, or no antidepressants on any pre-CABG hospital day and used Cox proportional hazards models to compare bleeding and mortality rates among the exposure groups while adjusting for potential confounders based on administrative data, pre-CABG charge codes, and discharge diagnosis codes. RESULTS: We identified 132,686 eligible patients: 7112 exposed to SSRIs, 1905 exposed to other antidepressants, and 123,668 unexposed. As compared with no exposure, neither SSRIs (hazard ratio [HR] 0.98; 95 % confidence interval [CI] 0.90-1.07) nor other antidepressants (HR 1.11; 95 % CI 0.96-1.28) increased major bleeds, and neither SSRIs (HR 0.93; 95 % CI 0.80-1.07) nor other antidepressants (HR 0.84; 95 % CI 0.62-1.14) increased mortality. Both SSRIs (HR 1.14; 95 % CI 1.10-1.18) and other antidepressants (HR 1.11; 95 % CI 1.03-1.19) were associated with a slight increase in receipt of one or more packed red blood cell (pRBC) units, but neither were associated with substantial increases in receipt of three or more pRBC units (HR 1.06; 95 % CI 0.96-1.17 for SSRIs; HR 1.09; 95 % CI 0.91-1.31 for other antidepressants). CONCLUSION: In this large cohort study, neither SSRIs nor other antidepressants were associated with elevated rates of major bleed, or in-hospital mortality.

Near-real-time monitoring of new drugs: an application comparing prasugrel versus clopidogrel.

BACKGROUND: Methods for near-real-time monitoring of new drugs in electronic healthcare data are needed. OBJECTIVE: In a novel application, we prospectively monitored ischemic, bleeding, and mortality outcomes among patients initiating prasugrel versus clopidogrel in routine care during the first 2 years following the approval of prasugrel. METHODS: Using the HealthCore Integrated Research Database, we conducted a prospective cohort study comparing prasugrel and clopidogrel initiators in the 6 months following the introduction of prasugrel and every 2 months thereafter. We identified patients who initiated antiplatelets within 14 days following discharge from hospitalizations for myocardial infarction (MI) or acute coronary syndrome. We matched patients using high-dimensional propensity scores (hd-PSs) and followed them for ischemic (i.e., MI and ischemic stroke) events, bleed (i.e., hemorrhagic stroke and gastrointestinal bleed) events, and all-cause mortality. For each outcome, we applied sequential alerting algorithms. RESULTS: We identified 1,282 eligible new users of prasugrel and 8,263 eligible new users of clopidogrel between September 2009 and August 2011. In hd-PS matched cohorts, the overall MI rate difference (RD) comparing prasugrel with clopidogrel was -23.1 (95 % confidence interval [CI] -62.8-16.7) events per 1,000 person-years and RDs were -0.5 (-12.9-11.9) and -2.8 (-13.2-7.6) for a composite bleed event outcome and death from any cause, respectively. No algorithms generated alerts for any outcomes. CONCLUSIONS: Near-real-time monitoring was feasible and, in contrast to the key pre-marketing trial that demonstrated the efficacy of prasugrel, did not suggest that prasugrel compared with clopidogrel was associated with an increased risk of gastrointestinal and intracranial bleeding.

Type of stress ulcer prophylaxis and risk of nosocomial pneumonia in cardiac surgical patients: cohort study.

OBJECTIVE: To examine the relation between the type of stress ulcer prophylaxis administered and the risk of postoperative pneumonia in patients undergoing coronary artery bypass grafting. DESIGN: Retrospective cohort study. SETTING: Premier Research Database. PARTICIPANTS: 21,214 patients undergoing coronary artery bypass graft surgery between 2004 and 2010; 9830 (46.3%) started proton pump inhibitors and 11,384 (53.7%) started H2 receptor antagonists in the immediate postoperative period. MAIN OUTCOME MEASURE: Occurrence of postoperative pneumonia, assessed using appropriate diagnostic codes. RESULTS: Overall, 492 (5.0%) of the 9830 patients receiving a proton pump inhibitor and 487 (4.3%) of the 11,384 patients receiving an H2 receptor antagonist developed postoperative pneumonia during the index hospital admission. After propensity score adjustment, an elevated risk of pneumonia associated with treatment with proton pump inhibitors compared with H2 receptor antagonists remained (relative risk 1.19, 95% confidence interval 1.03 to 1.38). In the instrumental variable analysis, use of a proton pump inhibitor (compared with an H2 receptor antagonist) was associated with an increased risk of pneumonia of 8.2 (95% confidence interval 0.5 to 15.9) cases per 1000 patients. CONCLUSIONS: Patients treated with proton pump inhibitors for stress ulcer had a small increase in the risk of postoperative pneumonia compared with patients treated with H2 receptor antagonists; this risk remained after confounding was accounted for using multiple analytic approaches.

Cardiovascular risk in rheumatoid arthritis: comparing TNF-α blockade with nonbiologic DMARDs.

BACKGROUND: Elevated tumor necrosis factor (TNF)-α likely contributes to the excess cardiovascular risk observed in rheumatoid arthritis. We compared the cardiovascular risk in rheumatoid arthritis patients starting a TNF-α blocking agent versus a nonbiologic disease-modifying antirheumatic drug (nbDMARD). METHODS: Subjects with rheumatoid arthritis participating in several different US insurance programs between 1998 and 2007 who received methotrexate were eligible. Those who added a TNF-α blocking agent were compared with subjects who added a nbDMARD in Cox regression models stratified by propensity score decile and adjusted for oral glucocorticoid dosage. We examined the composite cardiovascular end point of myocardial infarction, stroke, or coronary re-vascularization after 6 months. RESULTS: We compared 8656 new users of a nbDMARD with 11,587 new users of a TNF-α blocking agent with similar baseline covariates. Incidence rates per 100 person-years for the composite cardiovascular end point were 3.05 (95% confidence interval [CI], 2.54-3.65) for nbDMARDs and 2.52 (95% CI, 2.12-2.98) for TNF-α blocking agents. The hazard ratio (HR) for the TNF-α blocking agent compared with nbDMARD carrying the first exposure forward was 0.80 (95%, CI 0.62-1.04), while the HR for the as-treated analysis was 0.71 (95% CI, 0.52-0.97). The potential cardiovascular benefit of TNF-α blocking agents was strongest among individuals ≥65 years of age (HR 0.52; 95% CI, 0.34 -0.77; P for interaction = 0.075). CONCLUSION: Among subjects with rheumatoid arthritis, TNF-α blocking agents may be associated with a reduced risk of cardiovascular events compared with an nbDMARD. Randomized controlled clinical trials should be considered to test this hypothesis.

Adjuvant vancomycin for antibiotic prophylaxis and risk of Clostridium difficile infection after coronary artery bypass graft surgery.

OBJECTIVE: The incidence of hospital-acquired Clostridium difficile infection (CDI) has increased rapidly over the past decade; patients undergoing major surgery, including coronary artery bypass grafting (CABG), are at particular risk. Intravenous vancomycin exposure has been identified as an independent risk factor for CDI, but this is controversial. It is not known whether vancomycin administered for surgical site infection prophylaxis increases the risk of CDI. METHODS: Using data from the Premier Perspective Comparative Database, we assembled a cohort of 69,807 patients undergoing CABG surgery between 2004 and 2010 who received either a cephalosporin alone (65.1%) or a cephalosporin plus vancomycin (34.9%) on the day of surgery. Patients were observed for CDI until discharge from the index hospitalization. In these groups, we evaluated the comparative rate of postoperative CDI with Cox models; confounding was addressed using propensity scores. RESULTS: In all, 77 (0.32%) of the 24,393 patients receiving a cephalosporin plus vancomycin and 179 (0.39%) of the 45,414 patients receiving a cephalosporin alone had postoperative CDI (unadjusted hazard ratio [HR], 0.73; 95% confidence interval [CI], 0.56-0.95). After adjusting for confounding variables with either propensity score matching or stratification, there was no meaningful association between adjuvant vancomycin exposure and postoperative CDI (HR, 0.85; 95% CI, 0.61-1.19; and HR, 0.85; 95% CI, 0.63-1.15, respectively). Results of multiple sensitivity analyses were similar to the main findings. CONCLUSIONS: After adjustment for patient and surgical characteristics, a short course of prophylactic vancomycin was not associated with an increased risk of CDI among patients undergoing CABG surgery.

Heart failure risk among patients with rheumatoid arthritis starting a TNF antagonist.

BACKGROUND: While heart failure (HF) is associated with elevations in tumor necrosis factor (TNF)α, several trials of TNF antagonists showed no benefit and possibly worsening of disease in those with known severe HF. We studied the risk of new or recurrent HF among a group of patients receiving these agents to treat rheumatoid arthritis (RA). METHODS: We used data from four different US healthcare programmes. Subjects with RA receiving methotrexate were eligible to enter the study cohort if they added or switched to a TNF antagonist or another non-biological disease modifying antirheumatic drug (nbDMARD). These groups were compared in Cox regression models stratified by propensity score decile and adjusted for oral glucocorticoid dosage, prior HF hospitalisations, and the use of loop diuretics. RESULTS: We compared 8656 new users of a nbDMARD with 11 587 new users of a TNF antagonist with similar baseline covariates. The HR for the TNF antagonists compared with nbDMARD was 0.85 (95% CI 0.63 to 1.14). The HR was also not elevated in subjects with a history of HF. But, it was elevated prior to 2002 (HR 2.17, 95% CI 0.45 to 10.50, test for interaction p=0.036). Oral glucocorticoids were associated with a dose-related gradient of HF risk: compared with no use, 1≤5 mg HR 1.30 (95% CI 0.91 to 1.85), ≥5 mg HR 1.54 (95% CI 1.09 to 2.19). CONCLUSIONS: TNF antagonists were not associated with a risk of HF hospital admissions compared with nbDMARDs in this RA population.

Comparative effectiveness of preventative therapy for venous thromboembolism after coronary artery bypass graft surgery.

BACKGROUND: Controversy exists regarding the optimal preventative therapy for venous thromboembolism (VTE) after coronary artery bypass graft (CABG) surgery. We sought to compare the effectiveness and safety of the most commonly used regimens. METHODS AND RESULTS: We assembled a cohort of 92 699 patients who underwent CABG between 2004 and 2008, using the Premier database. Patients were categorized by method of VTE prevention initiated within 48 hours of surgery, including no preventative therapy (n=55 400), mechanical preventative therapy (n=21 162), subcutaneous unfractio--nated or low-molecular-weight heparin (n=10 718), subcutaneous fondaparinux (n=88), and concurrent mechanical-chemical therapy (n=5331). The incidence of VTE and major bleeding events within 6 weeks of CABG were compared, using multivariable and propensity score adjustment. The overall incidence of VTE for the entire cohort was 0.74%, and the incidence of major bleeding was 1.43%. VTE and bleeding events occurred with similar incidence in each of the patient categories (VTE: 0.70%, 0.79%, 0.81%, 1.14%, and 0.73%; major bleeding: 1.36%, 1.45%, 1.69%, 3.41%, 1.50%; no prevention, mechanical prevention, subcutaneous heparin, subcutaneous fondaparinux, concurrent mechanical-chemical prevention, respectively). Compared with receiving no prevention, the use of mechanical prevention or subcutaneous heparin did not significantly reduce the risk of VTE or change the risk of major bleeding (P=NS). CONCLUSION: Venous thromboembolism occurs infrequently after CABG. Compared with the use of no prevention, the administration of chemical or mechanical preventative therapies to CABG patients does not appreciably lower the risk of VTE. These data provide support for the common practice of administering no VTE preventative therapy after CABG, used for nearly 60% of patients within this cohort.

The comparative safety of opioids for nonmalignant pain in older adults.

BACKGROUND: Severe nonmalignant pain affects a large proportion of adults. Optimal treatment is not clear, and opioids are an important option for analgesia. However, there is relatively little information about the comparative safety of opioids. Therefore, we sought to compare the safety of opioids commonly used for nonmalignant pain. METHODS: We devised a propensity-matched cohort analysis that used health care utilization data collected from January 1, 1996, through December 31, 2005. Study participants were Medicare beneficiaries from 2 US states who were new initiators of opioid therapy for nonmalignant pain, including codeine phosphate, hydrocodone bitartrate, oxycodone hydrochloride, propoxyphene hydrochloride, and tramadol hydrochloride; none had a cancer diagnosis, and none were using hospice or nursing home care. Our main outcome measures were incidence rates and rate ratios (RRs) with 95% confidence intervals (CIs) for cardiovascular events, fractures, gastrointestinal events, and several composite end points. RESULTS: We matched 6275 subjects in each of the 5 opioid groups. The groups were well matched on baseline characteristics. The risk of cardiovascular events was similar across opioid groups 30 days after the start of opioid therapy, but it was elevated for codeine (RR, 1.62; 95% CI, 1.27-2.06) after 180 days. Compared with hydrocodone, after 30 days of opioid exposure the risk of fracture was significantly reduced for tramadol (RR, 0.21; 95% CI, 0.16-0.28) and propoxyphene (0.54; 0.44-0.66) users. The risk of gastrointestinal safety events did not differ across opioid groups. All-cause mortality was elevated after 30 days for oxycodone (RR, 2.43; 95% CI, 1.47-4.00) and codeine (2.05; 1.22-3.45) users compared with hydrocodone users. CONCLUSIONS: The rates of safety events among older adults using opioids for nonmalignant pain vary significantly by agent. Causal inference requires experimental designs, but these results should prompt caution and further study.

Maximum potential benefit of implantable defibrillators in preventing sudden death after hospital admission because of heart failure.

BACKGROUND: Implantable defibrillators are recommended for the prevention of sudden cardiac death in patients with heart failure. However, criteria to identify those who would benefit most from this therapy are lacking. We assessed the maximum potential benefit of preventing sudden death in patients with repeated hospital admissions because of heart failure. METHODS: Using a cohort assembled from an administrative database, we identified 14,374 patients admitted to hospital for the first time because of heart failure between Jan. 1, 2000, and Dec. 31, 2004. We followed subsequent admissions related to heart failure as well as mortality and causes of death to Mar. 31, 2006. We regarded all out-of-hospital cardiac deaths as sudden deaths. We calculated the maximum potential benefit of preventing sudden death by subtracting the observed survival after each hospital admission from the hypothetical survival whereby all out-of-hospital cardiac deaths were assumed to be preventable. RESULTS: The mean age of the cohort was 77 years, 45% were women, 11% had cerebrovascular disease, and 21% had chronic kidney disease. Out-of-hospital cardiac deaths constituted 13.7% (1226/8967) of all deaths during 32,055 person-years of follow-up. The median survival declined with each subsequent hospital admission related to heart failure. The hypothetical prevention of all out-of-hospital deaths prolonged life by 0.63 (95% confidence interval [CI] 0.49 to 0.77) years after the first hospital admission. This potential benefit dropped to 0.28 (95% CI 0.10 to 0.46) years after 3 hospital admissions related to heart failure. Among patients less than 65 years old, and older patients without kidney disease, dementia or cancer, more than 50% survived longer than 2 years until they had 2 or 3 hospital admissions related to heart failure. INTERPRETATION: The use of implantable defibrillators to prevent sudden death would provide limited benefit among older patients with comorbidities and among patients with multiple hospital admissions related to heart failure.

Evaluating the validity of an instrumental variable study of neuroleptics: can between-physician differences in prescribing patterns be used to estimate treatment effects?

BACKGROUND: Postmarketing studies of prescription drugs are challenging because prognostic variables that determine treatment choices are often unmeasured. In this setting, instrumental variable (IV) methods that exploit differences in prescribing patterns between physicians may be used to estimate treatment effects; however, IV methods require strong assumptions to yield consistent estimates. We sought to explore the validity of physician-level IV in a comparative study of short-term mortality risk among elderly users of conventional versus atypical antipsychotic medications (APM). METHODS: We studied a cohort of patients initiating APMs in Pennsylvania who were eligible for Medicare and a state-funded pharmaceutical benefit plan. The IV was defined as the type of the APM prescription written by each physician before the index prescription. To evaluate whether the IV was related to other therapeutic decisions that could affect mortality, we explored the association between the instrument and 2 types of potentially hazardous coprescriptions: a tricyclic antidepressant (TCA) not recommended for use in the elderly or a long-acting benzodiazepine. To insure that the IV analysis was not biased by case-mix differences between physicians, we examined the associations between the observed patient characteristics and the IV. RESULTS: The cohort consisted of 15,389 new users of APMs. Our multivariable model indicated that physicians who had most recently prescribed a conventional APM were not significantly more or less likely to coprescribe a potentially hazardous TCA [odds ratio (OR), 0.78; 95% confidence interval (CI), 0.58-1.02] but were less likely to prescribe a long-acting benzodiazepine (OR, 0.57; 95% CI, 0.45-0.72) with their current APM prescription. The association between long-acting benzodiazepine prescribing and APM preference was no longer significant when the analysis was restricted to primary care physicians (OR, 0.84; 95% CI, 0.62-1.15). Multivariable regression indicated that important medical comorbidities (eg, cancer, hypertension, stroke) were unrelated to the IV. CONCLUSIONS: The previous APM prescription written by the physician was unassociated with major medical comorbidities in the current patient, suggesting that the IV estimates were not biased by case-mix differences between physicians. However, we did find that the IV was associated with the use of long-acting benzodiazepines. This association disappeared when the study was restricted to the patients treated by primary care physicians. Our study illustrates how internal validation approaches may be used to improve the design of quasi-experimental studies.