Increased plasma concentrations of soluble CD40 ligand in acute coronary syndrome depend on in vitro platelet activation.
BACKGROUND
Soluble CD40 ligand (sCD40L) was suggested as a novel biomarker of cardiovascular risk. We examined the effect of preanalytical variation on the measurement of sCD40L concentration.


METHODS
From healthy control individuals (n = 20) and patients with acute coronary syndrome (ACS) (n = 20) or sepsis (n = 20), we obtained blood drawn into 5 tubes containing citrate or a mixture of citrate, theophylline, adenosine, and dipyridamole (CTAD). The tubes were incubated for 30 min at room temperature or 0 degrees C before a single or double centrifugation (15 min, 2500 g) at room temperature or 4 degrees C, respectively. sCD40L, beta-thromboglobulin (betaTG), and platelet factor 4 (PF4) concentrations were measured using immunoassays.


RESULTS
Concentrations of sCD40L were very low in all CTAD and citrated samples maintained at 0 degrees C (median < or = 0.076 microg/L). Although increased betaTG and PF4 confirmed disease-related in vivo platelet activation, sCD40L was not higher in patients than in controls. In contrast, if the samples were processed at room temperature, sCD40L was significantly higher in ACS patients than in controls (P <0.02 in CTAD and citrated plasma at room temperature). Moreover, the betaTG:PF4 ratio decreased in patient but not control CTAD samples, suggesting a greater susceptibility of patient platelets to in vitro activation.


CONCLUSIONS
Increased sCD40L concentrations resulted from in vitro platelet activation during sample preparation. Disease-related in vivo activation did not contribute to sCD40L concentrations in plasma. Therefore, published studies of sCD40L demand cautious interpretation, because their preanalytical conditions were not standardized.
Ivandic
Boris T
BT
Department of Medicine III, University of Heidelberg, Heidelberg, Germany. boris.ivandic@med.uni-heidelberg.de
Spanuth
Eberhard
E
Haase
Detlef
D
Lestin
Heiko-Gundmar
HG
Katus
Hugo A
HA
D000208:Acute Disease; D000368:Aged; D015415:Biomarkers / Q000097:blood; D001800:Blood Specimen Collection; D023201:CD40 Ligand / Q000097:blood*; D003324:Coronary Artery Disease / Q000175:diagnosis*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010949:Plasma; D015539:Platelet Activation; D010978:Platelet Factor 4 / Q000032:analysis; D012995:Solubility; D013577:Syndrome; D001620:beta-Thromboglobulin / Q000032:analysis
D015415:Biomarkers; D001620:beta-Thromboglobulin; D023201:CD40 Ligand; D010978:Platelet Factor 4