Appropriateness of Assumed Versus Absolute White Blood Cell Counts for Estimation of Malaria Parasite Density in Children Population in Ibadan Southwest Nigeria

Abstract

Estimation of malaria parasite density is important in diagnosis and assessment of individuals on antimalarial drugs. The use of either patient’s actual white blood cell (WBC) counts or an assumed value of 8000/mm3 to calculate malaria parasite density is still controversially discussed in literature. This study was carried out to investigate the agreement between the two methods of calculating malaria parasite density in children. Data on parasite and WBC counts were extracted from 796 case record forms of children aged 3 to 120 months who participated in four antimalarial clinical trials conducted between 1998 and 2014. Criteria for enrolment into the clinical trials included symptoms compatible with acute uncomplicated malaria, microscopically confirmed malaria parasitaemia of at least 1000/μL and absence of danger signs of severe malaria. All the studies received relevant ethical approval. A Bland Altman plots was used to show level of agreement or bias between the two methods. Male participants constituted 54.9%. Overall mean age was 47±31 months and mean WBC was 7807±4888/mm3. Geometric mean parasite density using assumed and actual WBC were 15,870 parasite/μL and 14,139 parasite/μL (ρ<0.001) respectively. Bland Altman plots showed that mean differences between parasite densities calculated from assumed and actual WBC densities were close to zero suggesting no remarkable systematic bias. Using an assumed white blood cell counts for calculating parasite density appears appropriate in children aged 3 to 12months for in Southwest Nigeria.