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

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.

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.

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.

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.

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.