[Platelet reference values in healthy children living in Mexico City]. / Valores plaquetarios de referencia en niños sanos residentes de la Ciudad de México.

INTRODUCTION: There are few studies on normal values of platelet parameters (number of plate-lets, mean platelet volume [MPV], thrombocytocrit, and platelet distribution width [PDW]) in children. The objective of this study was to determine the normal values of these platelet indices in healthy children who live in Mexico City, located 2240 meters above sea level. MATERIAL AND METHODS: 642 healthy children, between 2 and 16 years old, who had normal growth and developmental features and no history of treatment with drugs that alter platelets, were selected. The children fasted for 12 hours before their blood was collected by venipuncture of the arm. Platelet values, determined in an automatic counter (Cell Dyn 3000), were used in the statistical analysis to calculate the mean, standard deviation, and the 3, 50, and 97 percentiles of each data distribution, stratified by age and sex. Correlations between platelet count, MPV, PcT, and PDW, according to age and sex, were evaluated with linear regression statistics. RESULTS: The number of platelets presented a negative correlation with age (r = -0.31, p = 0.001), whereas the mean platelet volume showed a positive correlation (r = 0.29, p = 0.001). The platelet distribution width correlated positively (r = 0.13, p = 0.001) and thrombocytocrit, negatively (r = -0.08, p = 0.05), with no evident variation in relation to age or sex. CONCLUSIONS: The decrease of platelet number with the subsequent increase of mean platelet volume in relation to age possibly resulted from the platelets having become more efficient in carrying out their haemostatic function. The values of platelet indices obtained in this study were similar to those of children living at sea level and, therefore, may be used as reference values in pediatric patients with clinical problems related to these cells.