RETICULATED PLATELET COUNTS IN THE DIAGNOSIS OF ACUTE IMMUNE THROMBOCYTOPENIC PURPURA

Purpose: Bone marrow aspiration is often performed to diagnose childho od acute immune thrombocytopenic purpura (ITP) because no non-invasive investigation to confirm the diagnosis is routinely available. Reticu lated platelets (RPs)-young platelets characterized by a high RNA cont ent-increase with increased platelet production and may be useful in t he diagnosis of ITP. Methods: To assess the role of RP counts in disti nguishing ITP, we compared counts from 15 consecutive patients with IT P with counts from 20 patients with acute lymphoblastic leukemia (ALL) , 10 with aplasia, and 27 healthy normal children. Whole blood in edet ic acid (EDTA) was labelled with a platelet-specific monoclonal antibo dy and incubated with thiazole orange (TO). A standard gate was set to achieve a fluorescence value of 1.3 +/- 0.5% for control lyophilized platelets. Results: Patients with ITP had a mean (+/- 1 standard devia tion) RP level of 32.9 +/- 10.2%; patients with ALL, 6.6 +/- 3.1%; pat ients with aplasia, 3.4 +/- 2.0%; and normal patients, 7.9 +/- 2.9%. T he difference in RPs between the ITP group and the ALL, aplasia, and n ormal groups was highly significant (p <0.0001 each), with no signific ant difference between the non-TTP groups (p = 0.12). Conclusions: Mea suring RPs by this simple whole-blood cytometric technique discriminat ed very well between the acute ITP and non-ITP groups. This test has a strong positive predictive value and may prove very useful in the ass essment of childhood acute ITP and the screening of candidates for bon e marrow aspiration.