Propensity score matching and randomization

• Published in: Journal of clinical epidemiology Vol. 68; no. 7; pp. 760 - 768
• Main Authors: Mnatzaganian, George, Davidson, David C., Hiller, Janet E., Ryan, Philip
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.07.2015; Elsevier Limited
• Subjects: Aged; Ageism - statistics & numerical data; Arthritis; Arthroplasty, Replacement, Hip - utilization; Case-Control Studies; Channeling bias; Comorbidity; Confounding; Confounding Factors (Epidemiology); Elective Surgical Procedures - utilization; Elective total joint arthroplasty; Epidemiology; Health risk assessment; Humans; Internal and external validity; Internal Medicine; Joint surgery; Longitudinal Studies; Male; Mortality; Osteoarthritis, Hip - therapy; Patient Selection; Prognosis; Propensity Score; Propensity score matching; Random Allocation; Randomization; Risk Factors; Selection Bias; Socioeconomic Factors; Channeling bias; Internal and external validity; Randomization; Propensity score matching; Confounding; Elective total joint arthroplasty; Selection bias
• ISSN: 0895-4356; 1878-5921; 1878-5921
• DOI: 10.1016/j.jclinepi.2015.01.002

We used elective total joint replacement (TJR) as a case study to demonstrate selection bias toward offering this procedure to younger and healthier patients. Longitudinal data from 2,202 men were integrated with hospital data and mortality records. Study participants were followed from recruitment (1996–1999) until TJR, death, or 2007 (end of follow-up). A propensity score (PS) was constructed to quantify each subject's likelihood of undergoing TJR. TJR recipients were later matched to their non-TJR counterparts by PS and year of hospitalization. Ten-year mortality from index admission was compared between cases and controls. Overall, 819 (37.2%) had TJR. Those were younger, healthier, and belonged to higher socioeconomic classes compared with those who were not proposed for surgery. Of the TJR recipients, 718 were matched to 1,109 controls. Cases and controls had similar characteristics and similar years of follow-up from recruitment till index admission. Nonetheless, controls were more likely to die (39.5%) compared with 14.5% in TJR cases (P < 0.001). Selection for elective procedures may introduce bias in prognostic features not accounted for by PS matching. Caution must be exercised when long-term outcomes are compared between surgical and nonsurgical groups in a population at risk for that surgical procedure.