Comparative analysis of malaria parasite density using actual and assumed white blood cell counts.

Aim: To compare malaria parasite densities, calculated using the white cell counts (WBC) of individual children with a standard WBC count of 8.0 x 10(9)/L.

Methods: In a cross-sectional study, the prevalence of malaria WBCs and malaria parasite densities were estimated in 240 healthy Nigerian children aged 1-8 years.

Results: Of 240 children, 75 (31.25%) were infected with malaria, 69 (28.75%) with P. falciparum and 9 (3.75%) with other species. The mean (SD) WBC count was 5.1 (2.0) x 10(9)/L. There was an age-related significant difference in the mean WBC counts (t=2.000, p<0.05), with values higher in the under-5s [5.6 (2.0) x 10(9)/L] than in the > or =5-years group [5.0 (1.8) x 10(9)/L]. No significant difference was observed with regard to gender and malaria infection. The mean (SD) parasite densities of P. falciparum obtained using the assumed value of 8.0 x 10(9)/L [1936 (1119.5)] was significantly higher than the parasite densities estimated using the individual WBC counts [1140 (862.8) for P. falciparum] (p<0.0001).

Conclusion: Parasite density estimation using the assumed count of 8.0 x 10(9)/L might result in over-estimation of the parasite burden. The WBCs of individual patients should always be estimated when parasite density is required.