Diurnal variation of soluble CD40 ligand in patients with acute coronary syndrome. Soluble CD40 ligand and diurnal variation.

Introduction: We sought to investigate whether day-night variations occur in the concentration of circulating soluble CD40 ligand in patients with acute coronary syndrome, as this may have practical implications.

Materials And Methods: We assessed 70 consecutive ST-segment elevation myocardial infarction patients admitted into the Coronary Care Unit and 50 control subjects. Each subject was studied under strictly controlled light/dark conditions. Blood samples were drawn at 09:00 h (light phase) and 02:00 h (dark phase). Nocturnal blood samples were drawn by a trained nurse, with the help of a minute torch with a dim red light in order to avoid any direct lighting on the patient during sleep. The soluble CD40 ligand was measured using a commercially available ELISA.

Results: Soluble CD40 ligand levels showed no diurnal variations in control subjects. In the ST-segment elevation myocardial infarction group, however, soluble CD40 ligand concentration (pg/mL) in the light phase was significantly higher than that in the dark phase (167.3+/-63.2 vs 118.9+/-48.3 pg/mL, p<0.001).

Conclusions: The study shows for the first time the existence of diurnal variations in soluble CD40 ligand levels in ST-segment elevation myocardial infarction patients, which indicates the need for standardizing the time of blood sampling for the assessment of this molecule, at least in studies involving ST-segment elevation myocardial infarction patients.