title: The Quasi-cohort approach in pharmacoepidemiology: upgrading the nested case-control.
abstract: Observational studies of drug effects conducted using health care mega-databases often involve large cohorts with multiple time-varying exposures and covariates. These present formidable technical challenges in data analysis, necessitating sampling approaches such as nested case-control designs. The nested case-control approach is, however, baffling to medical journal readers, particularly the comparisons involving "cases" versus "controls" and the convoluted way in which forward-looking relations from exposure to outcome are extracted from backward-looking data. I propose a "quasi-cohort" approach involving alternative ways of data presentation and analysis that are more in line with the underlying cohort design, including the computation of quasi-rates, rate ratios, and quasi-rate differences. I illustrate the quasi-cohort approach using data from a study of pneumonia risk associated with inhaled corticosteroid use in a cohort of 163,514 patients with chronic obstructive pulmonary disease, including 20,344 who had the outcome event of pneumonia hospitalization during more than 304 million person-days of follow-up.
authors.affiliation: From the aDepartment of Epidemiology and Biostatistics, McGill University, Montreal, Quebec, Canada; and bMcGill Pharmacoepidemiology Research Unit, Centre for Clinical Epidemiology, Jewish General Hospital, Montreal, Quebec, Canada.
authors.forename: Samy
authors.initials: S
authors.lastname: Suissa
mesh_terms: D000305:Adrenal Cortex Hormones / Q000009:adverse effects / Q000627:therapeutic use; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000893:Anti-Inflammatory Agents / Q000009:adverse effects / Q000627:therapeutic use; D016022:Case-Control Studies; D015331:Cohort Studies; D003627:Data Interpretation, Statistical; D015340:Epidemiologic Research Design; D005260:Female; D006760:Hospitalization; D006801:Humans; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D017891:Pharmacoepidemiology / Q000379:methods*; D011014:Pneumonia / Q000139:chemically induced / Q000628:therapy; D029424:Pulmonary Disease, Chronic Obstructive / Q000188:drug therapy; D012307:Risk Factors
chemical_list: D000305:Adrenal Cortex Hormones; D000893:Anti-Inflammatory Agents