Use of the platelet histogram maximum in evaluating thrombocytopenia.

The purpose of this study was to compare the mean platelet volume (MPV) and the highest peak of the platelet volume distribution curve (maximum of the platelet histogram) with regard to their ability to discriminate between thrombocytopenia due to decreased platelet production or increased platelet destruction. A total of 156 children were studied. Twenty-eight had a diagnosis of idiopathic thrombocytopenic purpura (ITP) and 128 had a low platelet count due to decreased production. MPV and maximum of the platelet histogram were obtained by using the Coulter Counter Max M (Coulter Diagnostics, Hialeah, FL). A comparison of the sensitivity and specificity for the MPV and the maximum of the histogram has been made using the method of the receiver operating characteristic curves. The results show that the maximum of the histogram is superior to the MPV and is a highly effective test for the evaluation of thrombocytopenia. We recommend the use of the maximum rather than the MPV to help distinguish between ITP and thrombocytopenia secondary to decreased platelet production.