RESUMEN
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.