The STIB score: a simple clinical test to predict clopidogrel resistance.

Background: High platelet reactivity (HPR) to clopidogrel is associated with an increased risk of ischaemic complications during and after coronary interventions and concerns up to 50% of patients undergoing PCI.

Aim Of The Study: The aim of the study was to identify patients with HPR to clopidogrel using bedside clinical information obtained in the Stent Thrombosis In Belgium (STIB) trial.

Methods: Data on platelet reactivity using the VerifyNow® point-of-care assay were obtained in 844 patients undergoing PCI for stable coronary artery disease 12 to 24 hours after a 600-mg loading dose of clopidogrel was given. Demographic, clinical and baseline routine biological tests were obtained and compared with P2Y12 reaction units (PRU). Patients with PRU>230 (HPR) were considered as non-responders to clopidogrel.

Results: HPR was observed in 424/844 pts. Age, weight, body mass index (BMI), HPR to aspirin, diabetes, renal failure (MDRD<60 ml/min), haemoglobin (Hb), haematocrit, fibrinogen, glycaemia and glycated haemoglobin were associated with HPR to clopidogrel. In multivariate analysis, only Hb (OR: 0.77), BMI (OR: 1.06) and diabetes (OR: 1.62) emerged as independent risk factors. Hb<13.9 g/dl, BMI>28 kg/m2 and presence of diabetes were equally associated to predict HPR and can be added to derive a simple score to predict clopidogrel resistance. Although 38.5% of patients without a single clinical predictor still have HPR, 2/3 patients with 2 or 3 risk factors are resistant to clopidogrel.

Conclusions: STIB HPR score allows identification of patients with a high probability of resistance to clopidogrel based on diabetes, Hb<13.9 g/dl and BMI>28 kg/m2. This bedside clinical test could be useful for the identification of patients in whom another P2Y12 inhibitor should be recommended before and after PCI.