Staging and clean room: Constructs designed to facilitate transparency and reduce bias in comparative analyses of real-world data.

PURPOSE: We describe constructs designed to protect the integrity of the results from comparative analyses using real-world data (RWD): staging and clean room. METHODS: Staging involves performing sequential preliminary analyses and evaluating the population size available and potential bias before conducting comparative analyses. A clean room involves restricted access to data and preliminary results, policies governing exploratory analyses and protocol deviations, and audit trail. These constructs are intended to allow decisions about protocol deviations, such as changes to design or model specification, to be made without knowledge of how they might affect subsequent analyses. We describe an example for implementing staging with a clean room. RESULTS: Stage 1 may involve selecting a data source, developing and registering a protocol, establishing a clean room, and applying inclusion/exclusion criteria. Stage 2 may involve attempting to achieve covariate balance, often through propensity score models. Stage 3 may involve evaluating the presence of residual confounding using negative control outcomes. After each stage, check points may be implemented when a team of statisticians, epidemiologists and clinicians masked to how their decisions may affect study outcomes, reviews the results. This review team may be tasked with making recommendations for protocol deviations to address study precision or bias. They may recommend proceeding to the next stage, conducting additional analyses to address bias, or terminating the study. Stage 4 may involve conducting the comparative analyses. CONCLUSIONS: The staging and clean room constructs are intended to protect the integrity and enhance confidence in the results of analyses of RWD.

Migraine and risk of hypertensive disorders of pregnancy: A population-based cohort study.

BACKGROUND: Migraine is associated with hypertensive disorders of pregnancy through common pathophysiological features. This study evaluates the association between migraine diagnosis and treatment, and risk of hypertensive disorders of pregnancy. METHODS: We conducted a prospective cohort study in the Clinical Practice Research Datalink GOLD, a large longitudinal database of patient records in the UK. We analyzed data from liveborn or stillborn singleton deliveries from 1993-2020 with at least 24 months of medical history and no history of cardiovascular disease (n = 1,049,839). We ascertained migraine through diagnosis or prescription codes before 20 weeks of gestation and hypertensive disorders of pregnancy through diagnosis codes between 20 weeks of pregnancy and delivery. We used log-binomial regression models to estimate the risk ratio and 95% confidence intervals, comparing risk of hypertensive disorders of pregnancy among individuals with migraine to those without migraine, adjusting for confounders. CONCLUSIONS: A history of migraine prior to pregnancy was associated with an increased risk of hypertensive disorders of pregnancy (RR = 1.17, 95% CI: 1.09-1.26). The greatest risk was among those with pre-pregnancy migraine that persisted into the first trimester (RR = 1.84, 95% CI: 1.35-2.50). Use of migraine medication was associated with a higher risk of hypertensive disorders of pregnancy compared to non-migraineurs (RR = 1.50, 95% CI: 1.15-1.97). Results from this study indicate that migraine is a potential risk factor for hypertensive disorders of pregnancy.

Quality of rheumatoid arthritis recording in United Kingdom Clinical Practice Research Datalink Aurum.

PURPOSE: While several studies have assessed quality and completeness of recording acute medical events in Clinical Practice Research Datalink (CPRD) Aurum, evaluation of additional chronic conditions is warranted. METHODS: We selected patients with a first diagnosis of rheumatoid arthritis (RA) coded in their CPRD Aurum record between 2005 and 2019. We assessed quality of RA diagnosis by evaluating additional information in the patient record that would corroborate the diagnosis. We report recording of diagnoses, prescriptions, labs, and referrals expected to be present based on NICE guidelines for RA management. RESULTS: There were 53 083 patients with a first recorded RA diagnosis during the study period: 43606 (82%) patients had RA drug treatments in their record, 7596 (14%) had supporting codes without drug treatment, and 1881 (4%) patients had only a RA diagnoses recorded in their medical record with no supporting codes or RA treatments. Patients with RA diagnosis only were more likely to be first diagnosed in the earliest time period of study. Labs for diagnosing and monitoring RA were most common among patients with RA treatment. Analgesic and glucocorticoid prescriptions were common in all study patients but were highest among patients with RA treatment. Among patients with RA diagnosis only, the overwhelming majority had only one RA diagnosis recorded (76%). CONCLUSIONS: Our findings suggest that codes expected for monitoring and treatment of RA are routinely recorded in CPRD Aurum. These results support previous assessments, which found data recorded in CPRD Aurum to be of good quality for use in research.

Association between glycemic control and risk of venous thromboembolism in diabetic patients: a nested case-control study.

BACKGROUND: Previous studies suggested an elevated risk of venous thromboembolism (VTE) among patients with type 2 diabetes mellitus (T2DM), with a possible sex difference. The impact of glycemic control on the risk of VTE is unclear. Our objective was to analyze the association between glycemic control and the risk of unprovoked (idiopathic) VTE in men and women with T2DM. METHODS: We conducted a nested case-control analysis (1:4 matching) within a cohort of patients with incident T2DM between 1995 and 2019 using data from the CPRD GOLD. We excluded patients with known risk factors for VTE prior to onset of DM. Cases were T2DM patients with an unprovoked treated VTE. The exposure of interest was glycemic control measured as HbA1c levels. We conducted conditional logistic regression analyses adjusted for several confounders. RESULTS: We identified 2'653 VTE cases and 10'612 controls (53.1% females). We found no association between the HbA1c level and the risk of VTE in our analyses. However, when the most recent HbA1c value was recorded within 90 days before the index date, women with HbA1c levels > 7.0% had a 36-55% increased relative risk of VTE when compared to women with HbA1c > 6.5-7.0%. CONCLUSIONS: Our study raises the possibility that female T2DM patients with HbA1c levels > 7% may have a slightly higher risk for unprovoked VTE compared to women with HbA1c levels > 6.5-7.0%. This increase may not be causal and may reflect differences in life style or other characteristics. We observed no effect of glycemic control on the risk of VTE in men.

Characterization of the deterioration of diabetes control in patients with a subsequent diagnosis of pancreatic cancer: A descriptive study.

BACKGROUND: Deterioration of diabetes control can be the first harbinger of pancreatic cancer. However, little is known about how to distinguish patients with pancreatic cancer-related diabetes deterioration from those with type 2 diabetes progression. We aimed to characterize the glycated hemoglobin (HbA1c) and body weight profile of pancreatic cancer patients with deteriorating diabetes before the cancer diagnosis. METHODS: Using data from the UK-based Clinical Practice Research Datalink (CPRD) GOLD, we established a study population including pancreatic cancer patients with diabetes deterioration in the >0.5-3 years before the cancer diagnosis and non-cancer patients with deterioration of type 2 diabetes (comparison group). Patients were considered to have diabetes deterioration if their glucose-lowering treatment was intensified. We characterized the longitudinal trajectories of HbA1c and body weight in pancreatic cancer patients compared with non-cancer patients before and after treatment intensification. RESULTS: The mean absolute increase in HbA1c from the pre-deterioration period, i.e. the time >1-2 years before treatment intensification, to the time of treatment intensification, was 1.5% ± 1.6% in pancreatic cancer patients vs. 0.9% ± 1.4% in non-cancer patients. After treatment intensification, mean HbA1c remained elevated in pancreatic cancer patients, while it returned to the pre-deterioration level in non-cancer patients. Body weight decreased by 1.9% ± 6.4% in cancer patients and increased by 0.3% ± 5.2% in non-cancer patients between the pre-deterioration period and treatment intensification, on average. CONCLUSIONS: Pancreatic cancer-related diabetes deterioration may frequently be characterized by pronounced increases in HbA1c, persistent elevation of HbA1c after treatment intensification, and concomitant weight loss.

Pre-pregnancy migraine diagnosis, medication use, and spontaneous abortion: a prospective cohort study.

BACKGROUND: Migraine is common among females of reproductive age (estimated prevalence:17-24%) and may be associated with reproductive health through underlying central nervous system excitability, autoimmune conditions, and autonomic dysfunction. We evaluated the extent to which pre-pregnancy migraine diagnosis and medication use are associated with risk of spontaneous abortion (SAB). METHODS: We analyzed data from a preconception study of pregnancy planners (2013-2021). Eligible participants self-identified as female, were aged 21-45 years, resided in the USA or Canada, and conceived during follow-up (n = 7890). Participants completed baseline and bimonthly follow-up questionnaires for up to 12 months or until a reported pregnancy, whichever occurred first. Pregnant participants then completed questionnaires during early (~ 8-9 weeks) and late (~ 32 weeks) gestation. We defined migraineurs as participants who reported a migraine diagnosis or use of a medication to treat migraine. Preconception questionnaires elicited migraine medication use during the past 4 weeks, and SAB on follow-up and pregnancy questionnaires. We used Cox regression models with gestational weeks as the time scale to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for associations among preconception migraine, migraine medication use, and SAB, controlling for potential demographic, medical, and lifestyle confounders. RESULTS: Nineteen percent of study pregnancies ended in SAB. History of migraine before conception was not appreciably associated with SAB risk (HR = 1.03, 95% CI: 0.91-1.06). Use of any migraine medication was associated with a modest increase in SAB risk overall (HR = 1.14, 95% CI: 0.96-1.36). We observed the greatest increase in risk among those taking migraine medications daily (HR = 1.38, 95% CI: 0.81-2.35) and those taking prescription migraine prophylaxis (HR = 1.43, 95% CI: 0.72-2.84) or combination analgesic and caffeine medications (HR = 1.42, 95% CI: 0.99-2.04). CONCLUSIONS: Migraine medication use patterns suggesting greater underlying migraine severity were associated with increased risk of SAB. This research adds to the limited information available on the reproductive effects of migraine.

The Risk of Muscular Events Among New Users of Hydrophilic and Lipophilic Statins: an Observational Cohort Study.

BACKGROUND: Statins are effective lipid-lowering drugs for the prevention of cardiovascular disease, but muscular adverse events can limit their use. Hydrophilic statins (pravastatin, rosuvastatin) may cause less muscular events than lipophilic statins (e.g. simvastatin, atorvastatin) due to lower passive diffusion into muscle cells. OBJECTIVE: To compare the risk of muscular events between statins at comparable lipid-lowering doses and to evaluate if hydrophilic statins are associated with a lower muscular risk than lipophilic statins. DESIGN/SETTING: Propensity score-matched cohort study using data from the United Kingdom-based Clinical Practice Research Datalink (CPRD) GOLD. PATIENTS: New statin users. Cohort 1: pravastatin 20-40 mg (hydrophilic) vs simvastatin 10-20 mg (lipophilic), cohort 2: rosuvastatin 5-40 mg (hydrophilic) vs atorvastatin 10-80 mg (lipophilic), and cohort 3: simvastatin 40-80 mg vs atorvastatin 10-20 mg. MAIN MEASURES: The outcome was a first record of a muscular event (myopathy, myalgia, myositis, rhabdomyolysis) during a maximum follow-up of 1 year. KEY RESULTS: The propensity score-matched cohorts consisted of 1) 9,703, 2) 7,032, and 3) 37,743 pairs of statin users. Comparing the risk of muscular events between low-intensity pravastatin vs low-intensity simvastatin yielded a HR of 0.86 (95% CI 0.64-1.16). In the comparison of moderate- to high-intensity rosuvastatin vs equivalent doses of atorvastatin, we observed a HR of 1.17 (95% CI 0.88-1.56). Moderate- to high-intensity simvastatin was associated with a HR of 1.33 (95% CI 1.16-1.53), when compared with atorvastatin at equivalent doses. LIMITATIONS: We could not conduct other pairwise comparisons of statins due to small sample size. In the absence of a uniform definition on the comparability of statin doses, the applied dose ratios may not fully match with all literature sources. CONCLUSIONS: Our results do not suggest a systematically lower risk of muscular events for hydrophilic statins when compared to lipophilic statins at comparable lipid-lowering doses.

Antiseizure drugs and risk of developing smoking-related chronic obstructive pulmonary disease or lung cancer: A population-based case-control study.

AIMS: To determine whether enzyme-inducing antiseizure drugs (ASDs) affect the risk of developing chronic obstructive pulmonary disease (COPD) or lung cancer in smokers. METHODS: Cases of COPD and lung cancer and matched controls without these conditions were identified from a population of smokers with ≥1 prescription for any type of ASD in the Clinical Practice Research Datalink UK database of patients managed in primary care (1995-2016). A matched case-control study was performed utilising multivariate logistic regression analyses of exposure to enzyme-inducing ASDs compared to non-enzyme-inducing ASDs. The duration of ASD exposure and level of tobacco exposure were also assessed. RESULTS: We identified 5952 incident COPD and 1373 incident lung cancer cases, and 59 328 and 13 681 matched controls, respectively. Compared with never use, ever use of enzyme-inducing ASDs was associated with slightly decreased risk estimates of COPD (adjusted odds ratio: 0.85, 95% confidence interval: 0.81-0.89) and lung cancer (adjusted odds ratio: 0.82, 95% confidence interval: 0.73-0.92). These risk estimates were attenuated in heavy smokers. CONCLUSION: We found slightly decreased risk estimates of COPD and lung cancer among smokers taking enzyme-inducing ASDs and hypothesise that this may be related to induction of detoxification of tobacco-specific lung toxins.

Validity of bariatric surgery codes in the UK Clinical Practice Research Datalink (CPRD) GOLD compared with Hospital Episodes Statistics.

OBJECTIVES: To assess completeness and validity of bariatric surgery codes in the UK Clinical Practice Research Datalink (CPRD) GOLD compared with Hospital Episodes Statistics (HES). METHODS: We conducted a validation study among patients in the UK-based CPRD GOLD with linkage to HES (1998 to 2017). Since the same surgery codes are used for bariatric and other gastrointestinal surgery we assessed code distribution patterns used in patients with bariatric versus other gastrointestinal surgery by presence of other conditions such as obesity and gastrointestinal cancer. We developed algorithms to identify bariatric surgery and calculated validity measures (ie, positive/negative predictive value [PPV/NPV], sensitivity, and specificity) of each in CPRD GOLD compared with HES (gold standard). RESULTS: Among 7 357 007 available patients we identified 10 190 patients who had a total of 14 046 potential bariatric surgery codes in CPRD GOLD and/or HES. Surgery code patterns differed between bariatric surgery and assumed other gastrointestinal surgery. The sensitivity of CPRD GOLD bariatric surgery coding improved from an overall of 56% to 69-71% when applying stricter algorithms (ie, in obese patients or obese, gastrointestinal disease/complication free patients) but PPVs remained at 53%-55%. NPVs and specificities of CPRD GOLD bariatric surgery coding achieved ≥99.8% for all algorithms. CONCLUSION: Our results suggest that using CPRD GOLD and HES data and a wide selection of surgery codes will result in the most complete and accurate capture of bariatric surgery events. Validity measures of CPRD GOLD bariatric surgery codes were identical in obese patients and more restrictive populations.

CPRD Aurum database: Assessment of data quality and completeness of three important comorbidities.

PURPOSE: The Clinical Practice Research Datalink (CPRD) now provides a new medical record database, CPRD Aurum. This is the second of several studies being undertaken to assess the quality of CPRD Aurum data for research. METHODS: We included patients aged 20+, with at least one lab test result of any type from a random sample of 50 000 patients in CPRD Aurum. We assessed whether diagnosis codes for type 2 diabetes, hyperlipidemia, and iron deficiency or unspecified anemia were accompanied by supporting codes including lab results and treatments (correctness) and whether lab results, treatments, or other codes indicate a missing diagnosis record (completeness). RESULTS: Among 37 502 patients in CPRD Aurum, correctness of type 2 diabetes, hyperlipidemia, and anemia diagnoses was high (99%, 93%, and 97%, respectively). Completeness was only high for type 2 diabetes (94%-98%); completeness for hypercholesterolemia and anemia diagnoses was modest even when the presence of treatments and lab results indicated the conditions were likely present (51%-59% and 58%-70%, respectively). CONCLUSIONS: Our findings indicate that for studies of type 2 diabetes, hyperlipidemia, and iron deficiency or unspecified anemia, the diagnosis code is likely to be correct where present. However, a significant proportion of cases of hyperlipidemia or anemia will be missed if only diagnosis codes are used to select patients with these conditions. Researchers should consider using treatments, supporting codes, and, when available, lab data to supplement diagnosis codes and enhance case capture when including these conditions in studies using CPRD Aurum.

Quality and completeness of diagnoses recorded in the new CPRD Aurum Database: evaluation of pulmonary embolism.

PURPOSE: The Clinical Practice Research Datalink (CPRD) now provides a new medical record database, CPRD Aurum. This is the first of several studies being undertaken to assess the quality and completeness of CPRD Aurum data for research endeavors. METHODS: We identified patients with a pulmonary embolism (PE) diagnosis from a random sample of 50 000 patients in CPRD Aurum and compared the diagnoses using data from Hospital Episode Statistics (HES). We calculated the proportion of PE cases recorded in CPRD Aurum who also had a PE diagnosis recorded in HES. We also evaluated completeness by identifying all PE diagnoses in HES and calculating the proportion also present in CPRD Aurum. RESULTS: The study included 781 PE patients: 580 had a PE in CPRD Aurum, 632 had a PE in HES, and 431 had a PE in both. The proportion of patients with anticoagulated PE in CPRD Aurum confirmed by HES was 76.8%. The completeness of primary hospitalized PE HES events compared to CPRD Aurum was 79.1%. In most instances, there was a plausible explanation for the presence of a PE in only one of the two data sources. CONCLUSIONS: The results of this study are reassuring and suggest that the correctness (eg, quality, accuracy) and completeness of diagnosis information in CPRD Aurum are promising with respect to serious acute conditions that require medical attention. Evaluation of other data elements will provide additional insight into this new data resource and its utility for medical research.

Parkinson disease and the risk of epileptic seizures.

OBJECTIVE: To assess the association between incident Parkinson disease (PD) and subsequent incident epileptic seizures. METHODS: We conducted a retrospective cohort study with a nested case-control analysis using data from the U.K. Clinical Practice Research Datalink. We identified patients aged ≥40 years with an incident diagnosis of PD between 1995 and 2016 and a matched comparison group of PD-free individuals. We calculated crude incidence rates (IRs) with 95% confidence intervals (CIs) of epileptic seizures in PD patients and the PD-free comparison group, and corresponding crude incidence rate ratios (IRRs). In the nested case-control analysis, we calculated adjusted odds ratios (adj. ORs) of incident PD among cases with incident epileptic seizures and seizure-free controls overall and stratified by various seizure-provoking comorbidities. RESULTS: Among 23,086 incident PD patients and 92,343 PD-free individuals, we identified 898 patients with incident epileptic seizures. The crude IR of epileptic seizures in PD patients was 266.7/100,000 person-years (95% CI = 235.6-297.7), and in PD-free individuals it was 112.4/100,000 person-years (95% CI = 103.5-121.3; IRR = 2.37, 95% CI = 2.06-2.73). The adj. OR of epileptic seizures was 1.68 (95% CI = 1.43-1.98) in PD patients compared with PD-free individuals. PD patients with comorbid brain disorders (adj. OR = 12.36, 95% CI = 8.74-17.48) or with > 1 seizure-provoking comorbidity (adj. OR = 13.24, 95% CI = 10.15-17.25) were at the highest risk of epileptic seizures compared with PD-free individuals with no seizure-provoking comorbidities. INTERPRETATION: This study suggests that incident PD is associated with an increased risk of incident epileptic seizures. Ann Neurol 2018;83:363-374.

Weight change and blood glucose concentration as markers for pancreatic cancer in subjects with new-onset diabetes mellitus: A matched case-control study.

OBJECTIVES: To evaluate the potential of blood glucose levels and weight change before the onset of diabetes as predictors of pancreatic cancer among subjects with new-onset diabetes, that is, cancer-related diabetes versus normal type 2 diabetes. METHODS: We conducted a case-control study among subjects with new diabetes in the United Kingdom-based Clinical Practice Research Datalink. Cases were pancreatic cancer subjects with diabetes for ≤2 years before the cancer diagnosis (i.e., cancer-related diabetes). Controls were cancer-free, type 2 diabetic subjects matched to cases on age, sex, and diabetes duration. We calculated adjusted odds ratios (aORs) for pancreatic cancer as a function of both weight change and blood glucose before the onset of diabetes. RESULTS: Weight loss of 10.0%-14.9% at diabetes onset was associated with an aOR for pancreatic cancer of 3.58 (95% CI 2.31-5.54), loss of ≥15.0%, with an aOR of 4.56 (95% CI 2.82-7.36), compared with stable weight. Blood glucose levels of ≤5.1 mmol/L or 5.2-5.6 mmol/L before diabetes onset were associated with an increased risk of a pancreatic cancer diagnosis, with aORs of 2.42 (95% CI 1.60-3.66) and 2.20 (95% CI 1.45-3.35), respectively, when compared with blood glucose levels ≥6.3 mmol/L within >2-3 years before cancer detection. CONCLUSIONS: Weight loss as well as blood glucose levels in the normal range (and thus rapid development of hyperglycemia) before diabetes onset may be predictive of pancreatic cancer-related diabetes and may help target which subjects with new diabetes to refer for pancreatic cancer screening examinations.

Adverse events profile of oral corticosteroids among asthma patients in the UK: cohort study with a nested case-control analysis.

BACKGROUND: To evaluate the adverse events profile of oral prednisolone among adult asthma patients in the UK. METHODS: Using data from the UK-based Clinical Practice Research Datalink, we conducted a series of cohort studies to quantify incidence rates and incidence rate ratios, and a series of nested case-control analyses to estimate crude and adjusted odds ratios, of 11 different potential corticosteroid-related adverse events (bone-related conditions, hypertension, peptic ulcer, severe infections, herpes zoster, diabetes mellitus type 2, cataract, glaucoma, chronic kidney disease, affective disorders, and cardiovascular events). RESULTS: Between 165,900 and 269,368 asthma patients were included in each of the 11 cohorts, of whom between 836 and 16,192 developed an outcome of interest. Incidence rates per 1000 person-years of potential corticosteroid-related adverse events in patients with new current use of oral prednisolone ranged from 1.4 (95% confidence interval [CI], 1.0-1.8) for peptic ulcer to 78.0 (95% CI, 74.8-81.2) for severe infections. After adjusting for confounding, current oral prednisolone use was most strongly associated with an increased risk of severe infection, compared with non-use of prednisolone; OR 2.16 (95% CI, 2.05-2.27). There were smaller elevated risks of peptic ulcer, affective disorders, and cataract at higher doses, and marginally increased risks of herpes zoster, cardiovascular events, diabetes mellitus type 2, and bone related conditions, compared with non-use of prednisolone. We did not observe an association between oral prednisolone use and glaucoma, chronic kidney disease, or hypertension. CONCLUSION: Oral prednisolone use is associated with infections, gastrointestinal, neuropsychiatric, ocular, cardiovascular, metabolic, and bone-related complications among adult asthma patients.

Selective Serotonin Reuptake Inhibitors and Cataract Risk: A Case-Control Analysis.

PURPOSE: Use of selective serotonin reuptake inhibitors (SSRIs) has been associated with an increased cataract risk. We aimed to assess cataract risk after exposure to SSRI or to other antidepressant drugs in a large electronic primary care database. DESIGN: Case-control study. PARTICIPANTS: The study population was derived from the UK-based Clinical Practice Research Datalink (CPRD). We included patients with first-time cataract aged ≥40 years between 1995 and 2015 and an equal number of cataract-free controls matched on age, sex, general practice, date of cataract recording (i.e., index date), and years of history in the CPRD before the index date. METHODS: We conducted conditional logistic regression analyses adjusted for body mass index, smoking, hypertension, diabetes, and systemic steroid use. Exposure of interest was the number of SSRI prescriptions and prescriptions for other antidepressant drugs. We further explored mutually exclusive use of single SSRI substances. In sensitivity analyses, we shifted the index date backwards by 2 years, and we restricted our analyses to cases and controls without a prior glaucoma diagnosis. MAIN OUTCOME MEASURES: Relative risk estimates as odds ratios (ORs) with 95% confidence intervals (CIs). RESULTS: We identified 206 931 cataract cases and the same number of matched controls. Current long-term use of SSRI (≥20 prescriptions) was not associated with an increased cataract risk (adjusted OR, 0.99; 95% CI, 0.94-1.03). However, in a subset of patients aged 40 to 64 years, we found a slightly increased risk of cataract for long-term SSRI users (adjusted OR, 1.24; 95% CI, 1.15-1.34) compared with nonusers. CONCLUSIONS: In these data, use of SSRI was not associated with an increased risk of cataract. The slightly increased OR for individuals younger than 65 years of age in association with long-term SSRI use needs to be investigated in further studies.

The risk of Stevens-Johnson syndrome and toxic epidermal necrolysis in new users of antiepileptic drugs.

OBJECTIVE: Older antiepileptic drugs (AEDs) are known to cause Stevens-Johnson syndrome and toxic epidermal necrolysis (SJS/TEN). However, evidence for newer AED is sparse. We quantified risks of SJS/TEN in association with use of all AEDs in the United Kingdom. METHODS: In a matched case-control study of 480 previously validated SJS/TEN cases (1995-2013) we used conditional logistic regression to calculate odds ratios (ORs) with 95% confidence intervals (CIs), and calculated absolute risks of SJS/TEN within separate cohorts of new users of 28 AEDs. We assessed causality between drugs and SJS/TEN in each exposed case, using an adapted version of the algorithm of drug causality for epidermal necrolysis (ALDEN) score. RESULTS: We observed a strong association between SJS/TEN and new use of carbamazepine (OR 92.57, 95% CI 19.89-∞), phenytoin (OR 49.96, 95% CI 10.13-∞), and lamotrigine (OR 26.90, 95% CI 4.88-∞), where causality, according to the ALDEN score, was very probable or probable for most exposed cases. Absolute risks for SJS/TEN were highest for phenytoin (45.86 cases/100,000 exposed), lamotrigine (44.17 cases/100,000 exposed), and carbamazepine (20.38 cases/100,000 exposed). Despite increased ORs for valproate (40,941 exposed), gabapentin (116,037 exposed), pregabalin (59,967 exposed), and clobazam (4,300 exposed), ALDEN suggested no causal association. There were no observed cases of SJS/TEN among new users of levetiracetam (n = 96,77), clonazepam (n = 18,075), or topiramate (n = 11,307). SIGNIFICANCE: The results of our study are consistent with those of previous studies of SJS/TEN, which found increased risks of SJS/TEN in new use of carbamazepine, phenytoin, and lamotrigine. Despite frequent use, no ALDEN-score confirmed cases were observed in new users of valproate, gabapentin, pregabalin, levetiracetam, topiramate, or clonazepam.

Population-Based Study on the Epidemiology of Ménière's Disease.

BACKGROUND AND OBJECTIVE: Ménière's disease (MD) is a disorder of the inner ear typically showing recurrent acute episodes of vertigo, hearing loss, and tinnitus. Epidemiologic studies on MD are scarce. We assessed the incidence rates (IRs) of MD and describe the characteristics of MD cases, comparing them to control patients without recorded evidence of MD. STUDY DESIGN: We conducted a retrospective population-based follow-up study and a nested case-control analysis using data from the UK-based Clinical Practice Research Datalink. METHODS: We identified patients between 18 and 79 years of age with an incident MD diagnosis between January 1993 and December 2014. We assessed the IRs of betahistine-treated MD. In the nested case-control analysis, we matched 4 controls to each MD case on sex, age, general practice, years of active history in the database, and calendar time. We conducted a χ2 test to present p values in order to compare the prevalence of demographics, comorbidities, and co-medication between cases and controls. RESULTS: We identified 5,508 MD cases and 22,032 MD-free controls (65.4% females). The overall IR for MD in the UK was 13.1 per 100,000 person-years. More cases were female, and the mean age at diagnosis was 55.4 ± 13.7 years. Smoking and alcohol consumption were less prevalent among MD cases. Depression, other affective disorders, sleeping disorders, anxiety, and migraine were more prevalent among MD cases than among controls. CONCLUSIONS: MD is uncommon in primary care in the UK with a preponderance among females.

Validation of Stevens-Johnson syndrome or toxic epidermal necrolysis diagnoses in the Clinical Practice Research Datalink.

PURPOSE: To evaluate the validity of recorded diagnoses of Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) in the Clinical Practice Research Datalink (CPRD). METHODS: We identified patients with a diagnosis of SJS or TEN between 1995 and 2013 in the CPRD. We reviewed information from patient records, free text, and hospital episode statistics (HES) data, and excluded patients with no indication of a secondary care referral. Remaining patients were classified as probable, possible, or unlikely cases of SJS/TEN by two specialised clinicians or based on pre-defined classification criteria. We quantified positive predictive values (PPV) for all SJS/TEN patients and for patients categorised as 'probable/possible' cases of SJS/TEN, based on a representative subsample of 118 patients for whom we had unequivocal information (original discharge letters or HES data). RESULTS: We identified 1324 patients with a diagnosis of SJS/TEN, among whom 638 had a secondary care referral recorded. Of those, 565 were classified as probable or possible cases after expert review. We calculated a PPV of 0.79 (95% CI, 0.71-0.86) for all SJS/TEN patients with a recorded secondary care referral, and a PPV of 0.87 (95% CI, 0.81-0.93) for probable/possible cases. After excluding 14 false positive patients, our study population consisted of 551 SJS/TEN patients. CONCLUSIONS: Diagnoses of SJS/TEN are recorded with moderate diagnostic accuracy in the CPRD, which was substantially improved by additional expert review of all available information. We established a large population-based SJS/TEN study population of high diagnostic validity from the CPRD. Copyright © 2016 John Wiley & Sons, Ltd.

The risk of new onset depression in association with influenza--A population-based observational study.

IMPORTANCE: Case-reports provided evidence that influenza infections, particularly severe episodes, may exert neuronal damage in the CNS and thereby increase the risk of depression. OBJECTIVE: It was the aim of this study to analyse the association between influenza infections and the risk of developing incident depression. DESIGN: We conducted a case-control analysis between 2000 and 2013 using the large UK-based primary care database Clinical Practice Research Datalink (CPRD). SETTING: This database contains anonymous longitudinal data from primary care. At present, it contains over 100 million person-years of data from some 10 million active patients. PARTICIPANTS: We encompassed 103307 patients below the age of 80 years with an incident major depression diagnosis between 2000 and 2013, and matched each case to one control patient on age, sex, general practice, number of medical encounters, and years of history in the CPRD prior to the index date. EXPOSURE: Major depression diagnosis was identified by READ-codes based on ICD-10 codes (F32), with a minimum of three prescriptions for antidepressant drugs recorded after the diagnosis. MAIN OUTCOME: We calculated relative risk estimates of developing depression in association with previous influenza infections, stratified by the number, timing and severity of such events, and we adjusted for a variety of comorbidities, smoking status, alcohol intake, body mass index, use of oral corticosteroids, and benzodiazepines. RESULTS: Patients with a previous influenza infection had an increased risk of developing depression (OR 1.30, 95%CI 1.25-1.34) compared to patients with no history of influenza infections. A recent influenza infection recorded within 30-180 days prior to the index date yielded an adjusted 1.57 (95%CI 1.36-1.81), and an increasing number of previous influenza infections was associated with increasing odds ratios (⩾ 3 recorded influenza infections, adjusted OR 1.48, 95%CI 1.22-1.81). CONCLUSION: This study suggests that influenza infections are associated with a moderately increased risk of developing depression.

Influenza infections and risk of Alzheimer's disease.

Influenza may cause neuropsychiatric disorders, including confusion, delirium, convulsions, and encephalopathy. We conducted a case-control study to evaluate the association between diagnosed influenza and the risk of developing Alzheimer's disease (AD) using the UK-based Clinical Practice Research Datalink (CPRD). We identified 19,463 patients who developed an incident AD diagnosis between 1998 and 2013 and matched them 1:1 to dementia-free controls on age, sex, general practice, calendar time and number of years of recorded history. We calculated adjusted odds ratios (aORs) with 95% confidence intervals (CIs) of developing AD in association with previous influenza infections and stratified by number of infections prior to the AD diagnosis date. Patients with a previous influenza infection were not at an increased risk of developing AD as compared to those with no previous infection (aOR, 95% CI 0.94, 0.87-1.02) overall. Nor was increasing number of infections related to an increased risk of developing AD; the aOR (95% CI) for those with 1, 2, or ⩾3 episodes was 0.98 (0.90-1.07), 0.70 (0.56-0.88), and 0.92 (0.63-1.34), respectively. Presence of an underlying chronic inflammatory disease in those with an influenza infection did not increase the risk of developing AD (aOR, 95% CI 0.83, 0.71-0.96), either, and there was no association between the severity of influenza infections (based on recorded neurological or bacterial complications) and the risk of AD. In conclusion, considering the limitations of this large observational study, we found no association between influenza infections and the risk of developing AD.