Background Aspirin inhibits platelet aggregation by blocking thromboxane synthesis and has an antithrombotic effect. Patients with systemic lupus erythematosus (SLE) are at increased risk for thrombotic events and are frequently on aspirin treatment.

Objectives The aim of this study is to investigate the presence of aspirin resistance in SLE patients.

Methods Aspirin resistance is determined by Multiplate^R impedance aggregometer (Dynabyte GmbH, Munich, Germany). If the arachidonic acid induced testwas positive then it was repeated in presence of 1 mg/ml acetylic salicylic acid in the medium (ASA control, Dynabyte GmbH, Munich, Germany). Aspirin resistance was defined if TRAP induced and ASPI induced aggregation test values were between 800-1300 area under the curve and 300 AUC respectively. Disease activity in SLE patients were determined by using SELENA-Systemic Lupus Erythematosus Disease Activity Index (SLEDAI).

Results Twenty-six SLE patients (F/M: 24/2) who were on regular aspirin treatment were enrolled into the study. Mean age of the patients was 37,8±12,9 years. Twenty-five patients were on 100/day aspirin and one was on alternate day 100 mg aspirin. Aspirin resistance were determined in 5(19,2%) SLE patients. When the tests were performed by adding acetylic salicylic acid in the medium, all of these patients were responsive to the aspirin. The mean SELENA-SLEDAI score or the mean body mass index value was not different between the SLE patients with aspirin resistance and the SLE patients without aspirin resistance (p=NS for all).

Conclusions Aspirin resistance is not infrequent in SLE. Patient’s compliance to the aspirin treatment should be checked periodically.

Disclosure of Interest None Declared