In patients with malaria, parasitaemia is usually estimated by assuming 8000 white cell counts (WCC) per microlitre of blood. In a sample of 3044 African children under 5 years of age with uncomplicated falciparum malaria, parasitaemia estimated using standardised WCC was compared to parasitaemia calculated based on each child's own WCC. The two methods produced comparable results. However, WCC were >8000 in under-fives with an inverse relationship with age, resulting in the standard approximation method significantly underestimating parasitaemia in the youngest age group and overestimating parasitaemia in the oldest age groups.
Olliaro, P.; Djimdé, A.; Karema, C.; Mårtensson, A.; Ndiaye, J.L.; Sirima, S.B.; Dorsey, G.; Zwang, J. Standardised versus actual white cell counts in estimating thick film parasitaemia in African children under five. Tropical Medicine and International Health (2011) 16 (5) 551-554. [DOI: 10.1111/j.1365-3156.2011.02738.x]