Background: Diabetes mellitus type 2 (DM2) is associated with high platelet reactivity both in patients who do not receive antiplatelet drugs and in those treated with acetylsalicylic acid (ASA). The pathomechanism of this phenomenon has not beenfully understood.

Aim: 1. To evaluate variability of platelet reactivity in patients with DM2 treated with oral antidiabetic drugs and receivingchronic ASA therapy. 2. To identify independent predictors of high platelet reactivity during ASA therapy in patients with DM2.

Methods: We studied 171 patients with DM2 treated with oral antidiabetic drugs and receiving long-term treatment with75 mg of ASA daily, selected among the participants of the prospective AVOCADO study. Platelet function was simultaneously evaluated using 4 methods: 1. measurement of serum thromboxane B2 (TXB2) concentration; 2. measurement of urinary11-dehydrothromboxane B2 (11-dhTXB2) concentration; 3. VerifyNow® automated analyser; 4. PFA-100® automated analyser.High platelet reactivity was defined as at least 3 of the following criteria: 1. serum TXB2 concentration in the upper quartile;2. urinary 11-dhTXB2 concentration in the upper quartile; 3. value ≥ 550 aspirin reaction units (ARU) by VerifyNow®;4. collagen-epinephrine closure time (CEPI-CT) below median of readings other than 300 s by PFA-100®. In all patients, DM2 control was evaluated, insulin resistance was measured using HOMA-IR, and routine laboratory tests were performed, including full blood count, renal function parameters, and inflammation markers.

Results: Mean patient age was 67.8 years, and median duration of DM2 was 5 years. We found poor agreement between different tests of platelet function. ARU ≥ 550 (VerifyNow®) was found in 14.0% of patients, and CEPI-CT below median of readings other than 300 s (PFA-100®) was found in 32.8% of patients. Our criteria of high platelet reactivity were met by 9.9% of patients. In multivariate logistic regression analysis, independent predictors of high platelet reactivity despite ASA therapy included chronic heart failure, current smoking, and higher leukocyte count.

Conclusions: 1. Patients with DM2 are characterised by large variability of platelet reactivity, with little agreement between various methods. 2. Smoking, chronic heart failure, and subclinical inflammation may be associated with high platelet reactivity in patients with DM2 treated with ASA.