[Value of reticulated platelet counts in identifying thrombocytopenia aetiology]

This study was to evaluate the role of reticulated platelets (RP) assay in the distinguishing the different causes of thrombocytopenia. The RP and immature platelet fraction (IPF) were stained by a nucleic acid-specific dye oxazine, and assayed by XE-2100 blood cell counter with an upgraded software in the reticulocyte/optical platelet channel. RP and IPF were measured in 137 thrombocytopenic patients and 187 normal controls. The results showed that the mean IPF was 1.07% in normal controls, and 10.28% in 109 patients with immune thrombocytopenia (p<0.01), RP absolute value in ITP group was higher than that in control group, there was significant difference between them (p=0.036). The mean IPF was 10.47% in patients with primary immune thrombocytopenia (PITP), and 9.45% in patients with secondary ITP (SITP). There was no significant difference of IPF between PITP and SITP group (p=0.635), but IPF in these 2 groups both were significantly higher than the normal controls. The mean IPF in 28 thrombocytopenic patients with hypocellular marrow was 2.37%. There was no difference of IPF between thrombocytopenic patients with hypocellular marrow and the normal controls (p=0.252), but the absolute counts of RP in the former was significantly lower than in the latter (p<0.05). The IPF cut-off for a diagnosis of thrombocytopenia with hypercellular marrow was 2.45%, the sensitivity was 92.7% and specificity 94.1%. It is concluded that the whole-blood IPF measurement by XE-2100 blood cell counter is an useful screening test to differentiate patients with thrombocytopenia of different causes. An IPF above 2.45% has both a high sensitivity and specificity for a diagnosis of thrombocytopenia with a hypercellular marrow.