Objectives: We sought to examine the role of complement component C4 deficiencies on the effect of antibiotic treatment in patients with acute coronary syndrome (ACS).
Design: Patients with ACS (n=144) were randomly divided to receive a three-month treatment of clarithromycin or placebo and followed for major adverse coronary and cerebrovascular events (MACCEs) for 404.5 median days (range 138-924 days). The primary results indicated that clarithromycin prevented recurrent cardiovascular attacks. For the present study we performed serum C4 allotyping of C4A and C4B. The clarithromycin response was reanalyzed taking into account the deficiencies in the C4 allotypes.
Results: The prevalence of C4A deficiency, C4B deficiency or these combined were 29.2% (42/144), 39.6% (57/144) and 66.0% (95/144), respectively. In patients with C4 deficiencies clarithromycin treatment resulted in a reduced number of MACCEs and the best cumulative survival as compared with the placebo group (MACCE 18.8% versus 39.1%, respectively; Log rank test, p=0.015).
Conclusions: Only patients with ACS and C4 deficiencies seem to benefit from antibiotic treatment. This may explain the controversial results of secondary prevention trials of coronary artery disease and possibly serve as a pharmacogenomic marker for clarithromycin treatment.