Changes in haemoglobin and haematocrit values in children aged 6 to 13 1/2 years in Mexico city

Abstract

Levels of Hb, hematocrit (Ht) and mean corpuscular Hb concentration (MCHC) were determined in 523 boys and 350 girls, clinically healthy, ages 6.0-13.5 yrs, middle socio-economic class, living in Mexico City [Mexico]. In girls, no significant differences according to age were observed in Hb or MCHC; Ht was significantly greater at 10.5 than at 10.0 yr, without subsequent modifications. In boys, Hb and Ht had a 1st increase between 10.5 and 11.0 yr and a 2nd rise from 12.5 yr on; MCHC remained unchanged. Boys were 6-12 mo. behind girls in regard to Ht increase; Ht increased when boys and girls reached similar mean weights (34 kg), heights (138 cm) and surface areas (1.15 m2); concomitantly, they had progressed to stage 2 of sexual development. Clear sex differences began to appear at age 11.5 when boys had higher Hb and Ht values than girls. Hb and Ht changes in these children are apparently not related to chronological age but can be better interpreted if compared to weight, height, surface area or stage of sexual development.