Risk of acute pancreatitis among new users of empagliflozin compared to sulfonylureas in patients with type 2 diabetes: A post-authorization safety study.

PURPOSE: This study was undertaken to evaluate the potential risk of acute pancreatitis with empagliflozin in patients with type 2 diabetes (T2D) newly initiating empagliflozin. METHODS: Data from two large US claims databases were analyzed in an observational study of patients with T2D receiving metformin who were newly prescribed empagliflozin versus sulfonylurea (SU). Because dipeptidyl peptidase-4 inhibitors and glucagon-like peptide-1 receptor agonists have been associated with the risk of acute pancreatitis in some studies, patients on these agents were excluded. Using pooled analyses of data from the two databases (2014-2021), patients initiating empagliflozin were matched 1:1 within database to patients initiating SU using propensity scores (PS) that incorporated relevant demographic and clinical characteristics. Prespecified sensitivity analyses were performed for design parameters. RESULTS: The analyses identified 72 661 new users of empagliflozin and 422 018 new users of SUs, with both patient groups on concurrent metformin therapy. Baseline characteristics within treatment groups appeared to be similar across the 72 621 matched pairs. After mean follow-up of ~6 months, incidence rates of acute pancreatitis in the pooled matched cohort were 10.30 (95% confidence interval [CI] 9.29-11.39) events per 1000 patient-years (PY) for empagliflozin and 11.65 (95% CI 10.59-12.77) events per 1000 PY for SUs. On a background of metformin, patients newly initiating empagliflozin did not have an increased risk of acute pancreatitis compared with those initiating an SU (pooled PS matched hazard ratio 0.88 [0.76-1.02]) across 75621.42 PY of follow-up. CONCLUSIONS: The results of this voluntary post-approval safety study provide additional evidence that the use of empagliflozin for the treatment of T2D is not associated with an increased risk of acute pancreatitis.

Clarifying the causal contrast: An empirical example applying the prevalent new user study design.

PURPOSE: The prevalent new user design extends the active comparator new user design to include patients switching to a treatment of interest from a comparator. We examined the impact of adding "switchers" to incident new users on the estimated hazard ratio (HR) of hospitalized heart failure. METHODS: Using MarketScan claims data (2000-2014), we estimated HRs of hospitalized heart failure between patients initiating GLP-1 receptor agonists (GLP-1 RA) and sulfonylureas (SU). We considered three estimands: (1) the effect of incident new use; (2) the effect of switching; and (3) the effect of incident new use or switching, combining the two population. We used time-conditional propensity scores (TCPS) and time-stratified standardized morbidity ratio (SMR) weighting to adjust for confounding. RESULTS: We identified 76 179 GLP-1 RA new users, of which 12% were direct switchers (within 30 days) from SU. Among incident new users, GLP-1 RA was protective against heart failure (adjHRSMR = 0.74 [0.69, 0.80]). Among switchers, GLP-1 RA was not protective (adjHRSMR = 0.99 [0.83, 1.18]). Results in the combined population were largely driven by the incident new users, with GLP-1 RA having a protective effect (adjHRSMR = 0.77 [0.72, 0.83]). Results using TCPS were consistent with those estimated using SMR weighting. CONCLUSIONS: When analyses were conducted only among incident new users, GLP-1 RA had a protective effect. However, among switchers from SU to GLP-1 RA, the effect estimates substantially shifted toward the null. Combining patients with varying treatment histories can result in poor confounding control and camouflage important heterogeneity.

Characterizing Imbalance in the Tails of the Propensity Score Distribution.

Understanding characteristics of patients with propensity scores in the tails of the propensity score (PS) distribution has relevance for inverse-probability-of-treatment-weighted and PS-based estimation in observational studies. Here we outline a method for identifying variables most responsible for extreme propensity scores. The approach is illustrated in 3 scenarios: 1) a plasmode simulation of adult patients in the National Ambulatory Medical Care Survey (2011-2015) and 2) timing of dexamethasone initiation and 3) timing of remdesivir initiation in patients hospitalized for coronavirus disease 2019 from February 2020 through January 2021. PS models were fitted using relevant baseline covariates, and tails of the PS distribution were defined using asymmetric first and 99th percentiles. After fitting of the PS model in each original data set, values of each key covariate were permuted and model-agnostic variable importance measures were examined. Visualization and variable importance techniques were helpful in identifying variables most responsible for extreme propensity scores and may help identify individual characteristics that might make patients inappropriate for inclusion in a study (e.g., off-label use). Subsetting or restricting the study sample based on variables identified using this approach may help investigators avoid the need for trimming or overlap weights in studies.

Can Weight of Evidence, Quantitative Bias, and Bounding Methods Evaluate Robustness of Real-world Evidence for Regulator and Health Technology Assessment Decisions on Medical Interventions?

PURPOSE: High-quality evidence is crucial for health care intervention decision-making. These decisions frequently use nonrandomized data, which can be more vulnerable to biases than randomized trials. Accordingly, methods to quantify biases and weigh available evidence could elucidate the robustness of findings, giving regulators more confidence in making approval and reimbursement decisions. METHODS: We conducted an integrative literature review to identify methods for determining probability of causation, evaluating weight of evidence, and conducting quantitative bias analysis as related to health care interventions. Eligible studies were published from 2012 to 2021, applicable to pharmacoepidemiology, and presented a method that met our objective. FINDINGS: Twenty-two eligible studies were classified into 4 categories: (1) quantitative bias analysis; (2) weight of evidence methods; (3) Bayesian networks; and (4) miscellaneous. All of the methods have strengths, limitations, and situations in which they are more well suited than others. Some methods seem to lend themselves more to applications of health care evidence on medical interventions than others. IMPLICATIONS: To provide robust evidence for and improve confidence in regulatory or reimbursement decisions, we recommend applying multiple methods to triangulate associations of medical interventions, accounting for biases in different ways. This approach could lead to well-defined robustness assessments of study findings and appropriate science-driven decisions by regulators and payers for public health.

Strategy for Generating Blinded Evidence for Single-Arm Trials with External Controls Using Expert Review of Home Video.

INTRODUCTION: Neurodegenerative diseases cause developmental delays and loss of milestones in infants and children. However, scalable outcome measures that quantify features meaningful to parents/caregivers (P/CGs) and have regulatory precedence are lacking for assessing the effectiveness of treatments in clinical trials of neurodegenerative disorders. To address this gap, we developed an innovative, blinded strategy for single-arm trials with external controls using expert panel review of home video. METHOD: We identified meaningful, observable, and objective developmental milestones from iterative interviews with P/CGs and clinical experts. Subsequently, we standardized video recording procedures and instructions to ensure consistency in how P/CGs solicited each activity. In practice, videos would be graded by an expert panel blinded to treatment. To ensure blinding and quality control, video recordings from interim time points would be randomly interspersed. We conducted a pilot study and a pretest of grading to test feasibility and improve the final strategy. RESULTS: The five P/CGs participating in the pilot study found the instructions clear, selected activities important and reflective of their children's abilities, and recordings at-home preferrable to in-clinic assessments. The three grading experts found the videos easy to grade and the milestones clinically meaningful. CONCLUSION: Our standardized strategy enables expert panel grading of developmental milestone achievements using at-home recordings, blinded to treatment and post-baseline time points. This rigorous and objective scoring system has broad applicability in various disease contexts, with or without external controls. Moreover, our strategy facilitates flexible, continued data collection and the videos can be archived for future analyses.

Assessment of Codispensing Patterns of Mirabegron and Prespecified CYP2D6 Substrates in Patients with Overactive Bladder.

BACKGROUND: Patients with overactive bladder (OAB) experience sudden, intense urges to urinate, which may include urge urinary incontinence and nocturia. Pharmacotherapy includes ß3-adrenergic receptor agonists such as mirabegron; however, mirabegron contains a label warning for cytochrome P450 (CYP) 2D6 inhibition, making coadministration with CYP2D6 substrates require monitoring and dose adjustment to avoid unintended increases in substrate concentration. OBJECTIVE: To understand the codispensing patterns of mirabegron among patients using ten predefined CYP2D6 substrates with and before mirabegron dispensing. METHODS: This retrospective claims database analysis used the IQVIA PharMetrics® Plus Database to assess codispensing of mirabegron with ten predefined CYP2D6 substrate groups identified on the basis of medications most frequently prescribed in the United States, those with high susceptibility to CYP2D6 inhibition, and those with evidence for exposure-related toxicity. Patients had to be ≥ 18 years old before initiation of the CYP2D6 substrate episode that overlapped with mirabegron. The cohort entry period was November 2012 to September 2019, and the overall study period was 1 January 2011 to 30 September 2019. Comparisons of patient profiles at dispensing were made between time periods with and before mirabegron use in the same patient. Descriptive statistics were used to assess the number of exposure episodes, total duration of exposure, and median duration of exposure of CYP2D6 substrate dispensing with and before mirabegron. RESULTS: CYP2D6 substrate exposure periods totaling ≥ 9000 person-months were available before overlapping exposure to mirabegron for all ten CYP2D6 substrate cohorts. Median codispensing duration for chronically administered CYP2D6 substrates was 62 (interquartile range [IQR] 91) days for citalopram/escitalopram, 71 (105) days for duloxetine/venlafaxine, and 75 (115) days for metoprolol/carvedilol; median codispensing duration for acutely administered CYP2D6 substrates was 15 (33) days for tramadol and 9 (18) days for hydrocodone. CONCLUSIONS: In this claims database analysis, the dispensing patterns of CYP2D6 substrates with mirabegron displayed frequent overlapping of exposure. Thus, a need exists to better understand the outcomes experienced by patients with OAB who are at increased risk for drug‒drug interactions when taking multiple CYP2D6 substrates concurrently with a CYP2D6 inhibitor.

CYP2D6 Substrate Dispensing Among Patients Dispensed Mirabegron: An Administrative Claims Analysis.

BACKGROUND: Overactive bladder (OAB) is characterized by the presence of bothersome urinary symptoms. Pharmacologic treatment options for OAB include anticholinergics and ß3-adrenergic agonists. Use of ß3-adrenergic agonists may result in similar treatment efficacy with a decreased side effect profile compared with anticholinergics because high anticholinergic burden is associated with cardiovascular and neurologic side effects. However, the ß3-adrenergic agonist mirabegron, one of two approved drugs within this class, is a moderate cytochrome P450 (CYP) 2D6 inhibitor, and coadministration of drugs that are CYP2D6 substrates with mirabegron may lead to adverse drug effects. OBJECTIVE: The aim of this study was to quantify how often CYP2D6 substrates were dispensed in patients receiving mirabegron among adults of any age and among those ≥ 65 years of age. METHODS: In this retrospective descriptive analysis, a deidentified administrative claims database in the United States, IQVIA PharMetrics® Plus, was used to identify dispensing claims for CYP2D6 substrates and mirabegron from November 2012 to September 2019. Prevalence of CYP2D6 substrate dispensing was assessed in patients dispensed mirabegron among all adults ≥ 18 years old and additionally among a cohort of those ≥ 65 years old. Patient baseline profiles at the time of mirabegron and CYP2D6 substrate codispensing and at the time of mirabegron dispensing were compared. CYP2D6 substrates were categorized as those with the potential for increased risk of QT prolongation, with anticholinergic properties, with narrow therapeutic index (NTI), contraindicated or having a black box warning when used with CYP2D6 inhibitors, or used for depression or other psychiatric disease. Dispensing data and patient profiles were summarized descriptively. RESULTS: Overall, 68.5% of adults ≥ 18 years old dispensed mirabegron had overlapping dispensings for one or more CYP2D6 substrate; 60.6% and 53.6% had overlapping dispensings for CYP2D6 substrates with anticholinergic properties or risk of QT prolongation, respectively. CYP2D6 substrates with NTI, contraindicated with CYP2D6 inhibitors, or for psychiatric use were codispensed in 17.7%, 16.6%, and 38.0% of adult mirabegron users, respectively. Mirabegron users receiving one or more concurrent CYP2D6 substrate were more likely to be older, have more comorbidities and baseline polypharmacy, and have increased healthcare resource utilization compared with those without concurrent CYP2D6 substrates. Commonly codispensed CYP2D6 substrates included hydrocodone, oxycodone, tramadol, metoprolol, and tamsulosin. Findings were similar for patients in the older cohort (≥ 65 years old), with 72.1% receiving overlapping CYP2D6 substrates. CONCLUSIONS: Codispensing of CYP2D6 substrates, especially those with anticholinergic properties or risk of QT prolongation, was common among adults and older adults receiving mirabegron. Results highlight the need for improved awareness of CYP2D6 substrate prescribing among patients receiving pharmacologic treatment for OAB that inhibits the CYP2D6 pathway.

Risk of bias in non-randomized observational studies assessing the relationship between proton-pump inhibitors and adverse kidney outcomes: a systematic review.

BACKGROUND: Proton-pump inhibitors (PPIs) are widely prescribed as acid-suppression therapy. Some observational studies suggest that long-term use of PPIs is potentially associated with certain adverse kidney outcomes. We conducted a systematic literature review to assess potential bias in non-randomized studies reporting on putative associations between PPIs and adverse kidney outcomes (acute kidney injury, acute interstitial nephritis, chronic interstitial nephritis, acute tubular necrosis, chronic kidney disease, and end-stage renal disease). METHODS: We searched the medical literature within 10 years of 17 December 2020. Pre-specified criteria guided identification of relevant English language articles for assessment. Risk of bias on an outcome-specific basis was evaluated using the Risk of Bias in Non-randomized Studies of Interventions (ROBINS-I) tool by two independent reviewers. RESULTS: Of 620 initially identified records, 26 studies met a priori eligibility criteria and underwent risk of bias assessment. Nineteen studies were judged as having a moderate risk of bias for reported adverse kidney outcomes, while six studies were judged as having a serious risk of bias (mainly due to inadequate control of confounders and selection bias). We were unable to determine the overall risk of bias in two studies (one of which was assessed as having a moderate risk of bias for a different adverse kidney outcome) due to insufficient information presented. Effect estimates for PPIs in relation to adverse kidney outcomes varied widely (0.24-7.34) but associations mostly showed increased risk. CONCLUSION: Using ROBINS-I, we found that non-randomized observational studies suggesting kidney harm by PPIs have moderate to serious risk of bias, making it challenging to establish causality. Additional high-quality, real-world evidence among generalizable populations are needed to better understand the relation between PPI treatment and acute and chronic kidney outcomes, accounting for the effects of varying durations of PPI treatment, self-treatment with over-the-counter PPIs, and potential critical confounders.

Interpretation of the Meaningfulness of Symptom Reduction with Vibegron in Patients with Overactive Bladder: Analyses from EMPOWUR.

INTRODUCTION: Reductions in bothersome symptoms of overactive bladder (OAB) demonstrate improvement in clinical trials, but patient perception of meaningfulness of such improvement is lacking. In the 12-week phase 3 EMPOWUR trial, vibegron significantly reduced average daily number of micturitions, urgency episodes, and urge urinary incontinence (UUI) episodes vs placebo (P < 0.01 each). This analysis assessed meaningfulness of reductions in clinical endpoints observed in EMPOWUR using patient perception of improvement. METHODS: An anchor-based approach using Patient Global Impression of Change (PGI-C) applied to phase 2 data allowed predefining phase 3 responder definitions. To confirm in phase 3, median change from baseline at week 12 in average daily number of micturitions, urgency episodes, and UUI episodes was generated for each PGI-C category and pooled across treatments. Based on predefined meaningful responder definitions, percentages of patients achieving ≥ 15% reduction in micturitions (post hoc), ≥ 50% reduction in urgency episodes (predefined), and ≥ 75% (predefined) and ≥ 90% (post hoc) reduction in UUI episodes were determined for patients receiving vibegron or placebo. RESULTS: Across treatments, for micturitions, urgency episodes, and UUI episodes, median change from baseline to week 12 increased with greater subjective improvement based on PGI-C scores, and median reductions pooled across treatment groups were higher than the responder definitions that patients perceived as improved. Significantly more patients receiving vibegron vs placebo achieved ≥ 15% reduction in micturitions (56.3% vs 44.6%, respectively), ≥ 50% reduction in urgency episodes (39.5% vs 32.8%), ≥ 75% reduction in UUI episodes (49.3% vs 32.8%), and ≥ 90% reduction in UUI episodes (35.2% vs 23.5%) at week 12 (P < 0.05 each). CONCLUSION: Significantly more patients treated with vibegron vs placebo in EMPOWUR achieved meaningful reductions in micturitions, urgency episodes, and UUI episodes that were associated with patient-perceived improvement. Results of these analyses support the meaningfulness of reductions in clinical endpoints observed in the 12-week EMPOWUR trial. CLINICAL TRIALS REGISTRATION: ClinicalTrials.gov identifier, NCT03492281.

Efficacy of Vibegron and Mirabegron for Overactive Bladder: A Systematic Literature Review and Indirect Treatment Comparison.

BACKGROUND: In the absence of head-to-head trials, we performed an indirect treatment comparison of the ß3-adrenergic agonists vibegron and mirabegron in the treatment of overactive bladder (OAB). METHODS: PubMed, Embase, and Cochrane Library were searched for articles related to phase 3, double-blind, controlled trials of vibegron 75 mg and mirabegron 25/50 mg in patients with OAB. Efficacy outcomes included change from baseline at weeks 4, 12, and 52 in mean daily number of total urinary incontinence episodes and micturitions and mean volume voided/micturition. Effect size was computed as placebo-subtracted change from baseline (weeks 4, 12) or active control (tolterodine)-subtracted change from baseline (week 52) for each treatment group. Adverse events (AEs) are presented descriptively. RESULTS: After removal of duplicates, 49 records were identified, and after screening 9 met inclusion criteria for analysis. Vibegron showed significantly greater reduction in mean daily number of total incontinence episodes than mirabegron 25 mg at week 4, mirabegron 50 mg (weeks 4, 52), and tolterodine (weeks 4, 12) (P < 0.05, each) and significantly greater improvement in volume voided versus mirabegron 25 mg (week 12), mirabegron 50 mg (weeks 12, 52), and tolterodine (week 4) (P < 0.05, each). Confidence intervals of point estimates overlapped zero for all other comparisons of vibegron and mirabegron (25 or 50 mg) or tolterodine, indicating no significant differences between treatments for these time/endpoints. Urinary tract infection, hypertension, and dry mouth were the most commonly occurring AEs for vibegron, mirabegron, and tolterodine, respectively, in the short-term trials; hypertension was the most commonly occurring AE with all three treatments in the long-term trials. CONCLUSIONS: Vibegron was associated with significant improvement in total incontinence episodes versus mirabegron at 4 and 52 weeks and volume voided at 12 and 52 weeks. Improvement in micturitions was similar between vibegron and mirabegron or tolterodine. Incidence of AEs was generally comparable between vibegron and mirabegron.

Demonstrating that Real World Evidence Is Fit-For-Purpose to Support Labeling: Parallels to Patient Reported Outcomes in the Pursuit of Labeling Claims.

INTRODUCTION: In December 2021, U.S. Food & Drug Administration (FDA) will issue guidance on the use of real-world evidence (RWE) to support new indications or expanded product labeling. While difficult to foresee what FDA will require, learnings can be gleaned from previous paradigm shifts at FDA, such as for patient reported outcomes (PROs) in 2006-2009. METHODS: We contrast published requirements for justifying PROs as fit-for-purpose for a specific labeling claim with a potential approach to justify RWE as fit-for-purpose to support expanded labeling or a new indication. RESULTS: PRO labeling claims require a PRO Evidence Dossier that includes: specific wording of claim, clinical trial hypothesis structure and endpoint model, and justification that the PRO is relevant and meaningful to patients in the target population (content validity) with adequate psychometric properties. FDA's 2018 RWE Framework outlined critical considerations for using RWE to support regulatory decisions, including data quality, relevancy, provenance, and transparency. Strong parallels exist between the evidence required to justify that PROs are fit-for-purpose to support specific labeling claims and evidence to justify RWE as fit-for-purpose for specific research questions and labeling. Early discussion with FDA is encouraged. CONCLUSION: Drawing on parallels with use of PROs in labeling, RWE for regulatory purposes should be evaluated within the context of specific labeling or indication, specific study design and analysis plans, and the data attributes of data source. Sponsors seeking a new indication or labeling expansion based on RWE should justify that a specific data source and specific study design are fit-for-purpose.

Evaluating the Feasibility of Electronic Health Records and Claims Data Sources for Specific Research Purposes.

Data collected in real-world clinical settings are increasingly being used to evaluate therapeutic options. While in its infancy for research assessing effectiveness, especially comparative effectiveness in the regulatory environment, electronic health records (EHR) and administrative insurance claims data are used extensively by both manufacturers and regulators to evaluate post-marketing safety of products in the real world. The feasibility of using these data for analysis in a research study depends on the specific research question and the availability, quality and relevance of the collected data to address the scientific question. It is unlikely that any specific database could be 'qualified' for use across all research questions, even within a specific therapeutic area, due to dependence of feasibility on the elements of the specific research question. This paper describes considerations for determining whether EHR or claims data can be used for specific research purposes. A new structured approach for assessing the feasibility of these data in research is proposed. The framework builds on and considers whether each element of the PICOTS framework for well-structured research questions is adequately captured to allow for viable reliance on EHR and claims data for that specific scientific question. Practical examples and discussion of the limitations of RWD for research are given along with approaches for interpretation of analyses using RWD.

Masking in Pragmatic Trials: Who, What, and When to Blind.

Masking (or blinding) of treatment assignment is routinely implemented in classical randomized clinical trials (RCTs) to isolate the effect of the intervention itself and to minimize the potential for bias that could occur with traditional trials. Such biases could be introduced with the conduct, assessment of endpoints, management of conditions, analysis, and reporting when the treatment assignments are known. However, masking of treatments is not only complex but it hinders how generalizable the findings are to the "real world" clinical setting. Pragmatic RCTs (pRCTs) are intended to evaluate the effects of interventions within routine medical care, and as such, do not typically mask treatment groups; moreover, pRCTs assess comparators that are available in routine medical practice, not masked placebos. Whether pRCTs should be masked if intended for regulatory or other purposes has recently been questioned. The literature on pRCTs, while extensive, does not address how much actual benefit is gained from masking outcomes and how masking may affect the "real world" nature of a study. Here, we propose an approach to evaluate sources of bias, describe stakeholders in the conduct of pRCTs who are most likely affected, and offer a framework for considering how masking may be implemented effectively while maintaining generalizability.

Symptoms and Dietary Impact in Hypertriglyceridemia-Associated Pancreatitis: Development and Content Validity of Two New Measures.

BACKGROUND: Severe hypertriglyceridemia (sHTG) is a rare condition, complicated by episodes of acute pancreatitis (AP), which can cause pain and/or life-threatening multi-organ dysfunction. Currently, there are no disease-specific patient-reported outcome (PRO) measures evaluating symptoms or dietary impact for this condition. OBJECTIVE: The objective of this study was to explore patient-reported symptoms and impacts of sHTG and AP and develop new measures to capture the symptoms and dietary impacts of this condition using patient language. METHODS: In-depth, semi-structured concept elicitation interviews were conducted with 12 US-based participants to explore their experience and identify key symptoms and impact on dietary behavior, both during and between episodes of AP. Participants had a range of AP severity with a previous triglyceride reading > 1000 mg/dL, and at least one attack of AP within the last 12 months. Transcripts were coded using thematic analysis. RESULTS: Qualitative data analysis revealed the substantial burden of AP associated with sHTG. Participants reported experiencing symptoms, especially abdominal pain, both during and between attacks of AP, and discussed considerable diet changes to prevent or minimize future attacks. A conceptual model was refined, based on patient input, and reviewed by clinical experts to determine key concepts for inclusion within two PRO measures, one evaluating symptoms and another evaluating impact on dietary behavior. Items were drafted using patient-derived language. A 19-item symptoms measure [Hypertriglyceridemia and Acute Pancreatitis Symptom Scale (HAP-SS)] and a 6-item dietary impact measure (Hypertriglyceridemia and Acute Pancreatitis Dietary Behavior (HAP-DB) measure) were developed, both with a 24-h recall period. CONCLUSIONS: The qualitative analysis confirmed the substantial burden of AP associated with sHTG. This research resulted in development of two disease-specific PRO measures for use during and between attacks of AP. These measures are being utilized in a clinical trial, which will confirm content, structure, and psychometric properties.

Real-World Evidence: What It Is and What It Can Tell Us According to the International Society for Pharmacoepidemiology (ISPE) Comparative Effectiveness Research (CER) Special Interest Group (SIG).

On December 8, 2016, the New England Journal of Medicine published a sounding board on Real World Evidence (RWE)1 by the US Food and Drug Administration (FDA) leadership. While the value of RWE based on nonrandomized observational studies was appreciated, such as for hypothesis generating, safety, and measuring quality in healthcare delivery, the authors expressed concerns on the quality of data sources and the ability of methodologies to control for confounding. In response, we offer a few considerations regarding these concerns.

Variation in adherence to medications across the healthcare system in two comparative effectiveness research cohorts.

AIM: To assess heterogeneity in adherence to medications in two example comparative effectiveness research studies. PATIENTS & METHODS: We analyzed data from commercially insured patients initiating a statin or anticoagulant during 2005-2012. We calculated the cross-validated R2 from a series of hierarchical linear models to assess variation in 1-year adherence. RESULTS: There was less heterogeneity in adherence in the statin cohort compared with the anticoagulant cohort, where patient characteristics explained 7.2% of variation in adherence, and adding therapy and provider characteristics increased the proportion of variation explained to 8.0 and 8.5%, cumulatively. Random effects provided essentially no explanatory power, even in the statin cohort with large numbers of patients clustered within each pharmacy, prescriber and provider. CONCLUSION: The dependence of adherence on the healthcare system was stronger when the healthcare system influenced treatment choice and patient access to medication and when indications for treatment were strong.

Regression coefficient-based scoring system should be used to assign weights to the risk index.

OBJECTIVE: Some previously developed risk scores contained a mathematical error in their construction: risk ratios were added to derive weights to construct a summary risk score. This study demonstrates the mathematical error and derived different versions of the Charlson comorbidity score (CCS) using regression coefficient-based and risk ratio-based scoring systems to further demonstrate the effects of incorrect weighting on performance in predicting mortality. STUDY DESIGN AND SETTING: This retrospective cohort study included elderly people from the Clinical Practice Research Datalink. Cox proportional hazards regression models were constructed for time to 1-year mortality. Weights were assigned to 17 comorbidities using regression coefficient-based and risk ratio-based scoring systems. Different versions of CCS were compared using Akaike information criteria (AIC), McFadden's adjusted R2, and net reclassification improvement (NRI). RESULTS: Regression coefficient-based models (Beta, Beta10/integer, Beta/Schneeweiss, Beta/Sullivan) had lower AIC and higher R2 compared to risk ratio-based models (HR/Charlson, HR/Johnson). Regression coefficient-based CCS reclassified more number of people into the correct strata (NRI range, 9.02-10.04) compared to risk ratio-based CCS (NRI range, 8.14-8.22). CONCLUSION: Previously developed risk scores contained an error in their construction adding ratios instead of multiplying them. Furthermore, as demonstrated here, adding ratios fail to even work adequately from a practical standpoint. CCS derived using regression coefficients performed slightly better than in fitting the data compared to risk ratio-based scoring systems. Researchers should use a regression coefficient-based scoring system to develop a risk index, which is theoretically correct.