Re: Fluoroquinolone use and risk of aortic aneurysm and dissection: nationwide cohort study
We read with interest the recent study by Pasternak and colleagues on vascular complications from fluoroquinolone use (1). Despite the huge number of patients included, we have serious doubts about the validity of the study results and its implicit causation.
The difference in event rates is so small (0.05%) that even the slightest imbalances in the populations studied could bear major confounding effects. Although the authors meticulously included 47 covariates as predictors in their propensity score matching covering demographic information, medical history, prescription drugs, and healthcare use, they omitted major factors such as indication for the antibiotic prescription and more importantly the site of infection. Having a few percentage points higher abdominal infections (e.g. gastrointestinal or pyelonephritis) in one group could alter (a) the detection rate of abdominal aneurysms by a more careful clinically focused examination, (b) the vulnerability by adjacent inflammatory processes and (c) the chance of a slightly higher misdiagnosis of abdominal symptoms as infectious than an aortic process. As the primary differences were found primarily in the abdominal aorta, the above effects should be considered carefully
Even though the information on side effects of different antibiotics is of utmost interest, we have serious concerns that the results of the study, which could well influence future recommendations by the National Institute of Health on prescription procedures, are heavily affected by the above-mentioned biases, and that the implicit causation is not as strong (if existing at all) as suggested.
(1) BMJ 2018;360:k678
Competing interests: No competing interests