Haematological and biochemical indices in young African children: in search of reference intervals

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Abstract
The reference intervals of haematological and biochemical indices currently used in Africa are derived from data collected from populations living in industrialized countries. Few studies have been performed in Africa questioning the validity of these values when applied to local African populations. To provide reference intervals of haematological [haemoglobin (Hb), white blood cells (WBC), haematocrit (Htc) and platelets] and biochemical indices (ALT, creatinine and bilirubin) for children aged 1-4 from a rural area of southern Mozambique. Reference intervals were developed using the 2.5 and 97.5 centiles. Partition tests were performed to evaluate age and gender differences. Quantile regression models were estimated for those variables in which age partition was recommended. Deviances from linearity in the estimated models were evaluated using fractional polynomials of first or second degree. Agreement to classify normality, using the estimated reference intervals or values in use in a western paediatric hospital, was made using the kappa statistic. Reference intervals for Hb, WBC, Htc, platelets, ALT and creatinine show significant differences by age. Gender differences were observed for creatinine values, while for bilirubin there were no significant differences for age or gender. Estimated Hb and Htc reference intervals in African children were lower than the accepted western ones, while ALT values were higher in the former. Agreement between normal classification, using the estimated intervals or the western values, was from slight to fair. Reference intervals of haematological and biochemical indices based on results from western individuals of the same age are not in agreement with the estimated values for African children. These observed values should not be used as a rule to define normality, but are the ones usually found in this population where anaemia, malaria and high mortality rates are also common.