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.