Background: The importance of the role of monocytes in coronary artery disease (CAD) is well documented. An increased number of circulating monocytes is associated with higher incidence of CAD. Both environmental and genetic factors influence monocytosis. The latter have been extensively studied since the development of high-throughput genome-wide association studies. Several associations between polymorphisms and monocytosis were found among healthy individuals; the first example was rs7023923. The magnitude of the association of studied polymorphisms with the trait of interest is often confounded by environmental factors and may therefore differ between patient and healthy populations. It is very important to determine the magnitude of the association among patients to predict outcome of the disease, e.g. myocardial infarction.

Aim: To determine whether the magnitude of association of rs7023923 with monocytosis, previously reported among healthy volunteers, is similar in patients in whom diagnosis of CAD was determined during elective coronarography.

Methods and results: Leucocytosis and neutrophilocytosis were higher among patients with CAD, while thrombocytosis was lower. Monocyte count did not differ among the studied groups (p = 0.25). We confirmed the association of rs7023923 with monocytosis among healthy blood donors (p = 0.0156) but not among patients admitted for elective coronarography (p = 0.61). Inclusion of the age and sex of patients in the statistical model did not modify the results.

Conclusions: Our data suggest that translation of the results of genetic association with the studied traits from healthy to patient population should be implemented with caution. It is possible that numerous environmental factors, which discriminate healthy volunteers from CAD patients, confound the magnitude of genetic associations and make interpretation of the data in patients less clear.