Journal Club Summary
Ray WA, Murray KT, Hall K, Arbogast PG, Stein CM. N Engl J Med. 2012 May 17;366(20):1881-90
This retrospective cohort study found that there was a slight increased risk of cardiovascular death in patients who received a 5-day course of azithromycin compared to propensity-score matched controls who took either no antibiotics or a 10-day course of amoxicillin (cumulative incidence = 85.2 cardiovascular deaths/ million courses of azithromycin, NNH = 18549, HR 2.88, 95% CI 1.79-4.63 and HR 2.49, 95% CI 1.38-4.50). JC attendees agreed that this study may not have adequately balanced cardiovascular risk between cohorts as there was no documentation of several cardiovascular risk factors relevant to the occurrence of arrhythmias.
By: Dr. Joanna Moore
(Presented March 2013)
Large population cohort studies are really the only method available for searching for associations between drugs and rare but serious adverse effects. Because there are so many potential confounders, high quality studies will attempt to adjust for these – propensity score matching is one method of confounder adjustment. Propensity score matching involves calculating conditional probabilities of having a certain outcome given the presence of pre-selected covariates (e.g. risk factors for a given outcome) and matching exposed and control subjects with similar propensity scores.
By: Dr. Lisa Calder