Evaluation of the diagnostic performance of platelet-derived indices for the differential diagnosis of thrombocytopenia in pediatrics

摘要

Antecedentes. Los índices plaquetarios tienen buena correlación con la etiología de la trombocitopenia en estudios realizados en adultos. Estos son: volumen plaquetario medio, ancho de distribución plaquetaria y porcentaje de plaquetas grandes. Objetivo. Determinar las características de los índices plaquetarios en población pediátrica con trombocitopenia y su posible correlación etiológica. Materiales y métodos. Estudio de prueba diagnóstica observacional analítico. Realizado con pacientes entre 6 meses y 18 años ingresados en un período de 18 meses con trombocitopenia 100x109/L. Resultados. 54 pacientes: 18 (33,3%) con púrpura trombocitopénica inmune y 36 (66,7%) con leucemia aguda. Edad media para púrpura trombocitopénica inmune 7,4 años y 6,8 para leucemia aguda. Valores de ancho de distribución plaquetaria con media de 15,08 fL en púrpura trombocitopénica inmune y 10,73 para leucemia aguda. Media del volumen plaquetario medio para púrpura trombocitopénica inmune 11,7 fL y de 9,8 fL para leucemia aguda. Porcentaje de plaquetas grandes la media para púrpura trombocitopénica inmune 38,26% y 24,97% para leucemia aguda. Las diferencias de los tres índices para cada una de las enfermedades fueron estadísticamente significativas (p=0,00). Las curvas de Característica Operativa del Receptor de los índices plaquetarios fueron parámetros suficientes para distinguir las causas de trombocitopenia: volumen plaquetario medio y porcentaje de plaquetas grandes con un área bajo la curva de 0,89 y 0,88 y ancho de distribución plaquetaria 0,903. Conclusiones. Los índices plaquetarios fueron útiles para el acercamiento inicial al diagnóstico diferencial de trombocitopenias en niños. Palabras clave: Trombocitopenia; Púrpura Trombocitopénica Idiopática; Volumen Plaquetario Medio (DeCS). Aponte-Barrios NH, Linares-Ballesteros A, Sarmiento-Urbina IC, Uribe-Botero GI. Evaluación del rendimiento diagnóstico de los índices plaquetarios en el diagnóstico diferencial de las trombocitopenias en pediatría. Rev Fac Med. 2014;62(4):547-52. http://dx.doi.org/10.15446/revfacmed.v62n4.43754. Introduction Among the studies that evaluate the usefulness of platelet-derived indices for the differential diagnosis of the causes of thrombocytopenia, some can be found that show how mean platelet volume (MPV), platelet distribution width (PDW), and platelet-large cell ratio (P-LCR) have a good diagnostic correlation when compared to findings from the study of bone marrow. Among the studies carried out to determine differential diagnoses, it is worth mentioning thrombocytopenia secondary to disease of the bone marrow or to diseases that reduce platelet life-span (1,2), immune thrombocytopenic purpura and aplastic anemia (3-5), or thrombocytopenia due to megaloblastic anemia and other causes (6). These studies have been performed on the adult population, but never on the pediatric population. Diagnostic methods for the study of blood cells and their assessment has advanced greatly: the techniques for their analysis have been simplified, and new methods have been developed that allow us to evaluate the different parameters that, today, are highly useful for the diagnosis of diverse pathologies (7). At present, we have hematology analyzers at our disposition that provide quick and very precise results that, in addition, have the capacity to measure blood cell parameters automatically. Among these parameters are the platelet-derived indices that generally are not used in the clinical context mainly because of an ignorance of their possible usefulness and, occasionally, because of difficulties encountered between laboratories related to the standardization of values. It is important to be aware of the reference interval that could be useful for the diagnosis of certain pathologies (3, 6-10, 12). The cut-off points used to define the indices in the studies of adult populations that were reviewed are: MPV of 8.4-12 femtoliters, 8-14 femtoliters for the platelet distribution width, and greater than 12 fL for the platelet-large cell ratio (3,6,9). The platelet-derived indices available in automated equipment are: mean platelet volume, platelet distribution width, and the platelet-large cell ratio. The mean platelet volume is a parameter that measures the average platelet size just as mean corpuscular volume does for red blood cells (3,6,10). The platelet distribution width expresses the variation in the size of the platelets and has shown usefulness in the differential diagnosis between reactive thrombocytosis and thrombocytosis associated with myeloproliferative disease. Furthermore, it works to differentially diagnose thrombocytopeni