Diabetic patients have a higher prevalence of inadequate platelet response to Clopidogrel. However, determinants of this low response remain uncertain.

We analyzed ADP-induced platelet aggregation (ADP-Ag), and Platelet Reactivity Index of Vasodilatator- Stimulated Phosphoprotein (PRI VASP) in 124 diabetic patients treated with Clopidogrel, and repeated them after glycemic optimization in 15 uncontrolled patients.

Platelet tests did not correlate with glycemic control and did not change after glycemic optimization. Type 2 diabetics had higher ADP-Ag and PRI VASP than type 1 (49±19 vs 33±19 %, p = 0.008; 62±16 vs 48±27 %, p = 0.02, respectively). On adjustment for studied variables ADP-Ag but not PRI VASP remained statistically associated with the type of diabetes (p = 0.007; p=0.11 respectively). Also fibrinogen was an independent predictor of ADP-Ag and clopidogrel non responders had elevated plasma fibrinogen, compared with responders: 8.2 ± 0.5 versus 3.8 ± 0.1g/L (p<10⁻⁴). A threshold of 3.57g/L led to a negative predictive value of 94.7 %.

Platelet response to clopidogrel, mainly ADP-Ag was not related to glycemic control but to the type of diabetes. Moreover fibrinogen strongly predicted ADP-Ag in diabetics.