Immune thrombocytopenia (ITP) is an autoimmune disorder characterized by abnormally low platelet count in the peripheral blood. It most commonly occurs when circulating antiplatelet antibodies attack and destroy platelets in the patient's blood. ITP can affect all age groups, with the incidence increasing with age. The diagnosis is formally made by eliminating all other known causes of secondary thrombocytopenia. The purpose of this research was to establish the role of antiplatelet antibodies in the diagnostic algorithm of thrombocytopenia, specifically whether specific antiplatelet antibodies test can be used to make the diagnosis of ITP. A retrospective research including 116 patients observed for thrombocytopenia was conducted in the period from January 1st to December 31st 2020 in the Clinical Hospital Centre Zagreb. Antiplatelet antibodies test was performed in every patient and the findings were used to determine specificity of the test in the diagnosis of ITP. Established diagnoses of thrombocytopenia and findings from the antiplatelet antibodies test were compared thus leading to sensitivity and specificity of the test in making the diagnosis of ITP. The test showed sensitivity of 13.8% and specificity of 95.8%. Positive antiplatelet antibodies test specific for ITP has a great value in making the diagnosis, and a negative test does not rule out the possibility of immune-mediated aetiology of the disease.