QJM Advance Access published online on April 8, 2008
QJM, doi:10.1093/qjmed/hcn047
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Reticulated platelets as a screening test to identify thrombocytopenia aetiology
From the 1Internal Medicine Department, 2Immunology Laboratory and 3Hematology Service, Hospital de Sabadell, Institut Universitari Parc Tauli—UAB, Sabadell, Barcelona, Spain
Address correspondence to M. Monteagudo, Internal Medicine Department, Hospital de Sabadell, Parc Taulí S/N, 08208 Sabadell, Barcelona, Spain. email: MMonteagudo{at}tauli.cat
Received 9 October 2007 and in revised form 11 March 2008
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Abstract |
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Background: Thrombocytopenia is a common haematological abnormality and no simple diagnostic test is available to diagnose thrombocytopenia pathogenesis.
Aim: To evaluate sensitivity and specificity of reticulated platelets (RP) as a diagnostic test for thrombocytopenia with increased thrombopoietic activity.
Design: Prospective observational study in thrombocytopenic patients.
Methods: A direct, whole-blood, dual-labelling flow cytometric method was used. Direct, whole-blood double coverage was achieved using a monoclonal anti-glycoprotein (GP)-III antibody (CD61 PerCP®) for platelet identification and thiazole orange (Retic-count®) as platelet mARN stain.
Results: RP were measured in 101 thrombocytopenic patients and 104 non-thrombocytopenic controls. The mean RP percentage in 60 thrombocytopenic patients with no increased thrombopoietic activity was 7.5% (CI for 95%: 5.2–9.7) and RP absolute number was 3.2 x 109/l (CI for 95%: 2.1–4.3). The mean RP percentage in 41 thrombocytopenic patients with increased thrombopoietic activity was 30.3% (CI for 95%: 25.1–35.5) and RP absolute number was 6.2 (CI for 95%: 4.8–7.7). The RP percentage cut-off for a diagnosis of thrombocytopenia with increased thrombopoietic activity was 11% [sensitivity 93%, specificity 85%, positive predictive value (PPV) 83%, negative predictive value (NPV) 95%].
Conclusions: RP measurement by flow cytometry, directly from whole-blood, is a useful screening test to differentiate between thrombocytopenia with high or low thrombopoietic activity. A RP percentage in excess of 11%, has a high sensitivity and good specificity for a diagnosis of thrombocytopenia with increased thrombopoietic activity.