Seasonal and sex-specific variations in haematological parameters in 4 to 5.5-month-old infants in Guinea-Bissau, West Africa.

Objective: This study investigated seasonal and sex-specific variations in the haematological parameters and established reference ranges for these parameters in healthy 4 to 5.5-month-old infants in Guinea-Bissau. Methods: Within a randomised trial of early measles vaccination, over a period of 13 months blood samples were collected from infants aged 4 to 5.5 months. Haematological parameters were determined by an automated cell counter and compared in linear regression models providing geometric mean ratios (GMR). Results: Blood samples from 501 infants (n= 248 boys, 49.5%) were obtained, and 285 (56.9%) were collected in the rainy season. Median age was 4.7 months (range 3.7 to 7.2 months). Eosinophil and platelet counts were lower in the dry season (December to May) than in the rainy season (GMR 0.79 [95% CI 0.68-0.92]) and 0.93 [0.87-1.00], respectively). The calculated reference ranges were wider and generally higher than those from a US population of comparable age, but neutrophil levels were notably lower in Guinea-Bissau. Conclusions: The study indicated that eosinophil and platelet counts of infants were subject to seasonal variations. The reference ranges for haematological values were comparable to other African populations and corroborated that neutropenia regularly occurs in African infants.