Efficacy of Absolute White Blood Cell Count in the Determination of Malaria Parasite Density among subjects presenting to University of Calabar Teaching Hospital.

Abstract

Malaria is a mosquito-borne infectious disease of animals and humans caused by parasitic protozoans in the genus Plasmodium. In 2016, there were an estimated 216 million cases of malaria in 91 countries, an increase of 5 million cases over 2015. The African region is home to 90% of malaria cases and 91% of malaria deaths. Children under 5 years and pregnant women are particularly susceptible to infection. White blood cells count (WBC) is used in the computation of malaria parasite density. Generally, in field surveys, standard WBC counts recommended by the WHO are used in the determination of malaria parasite density. Two microliter (2µl) and 6µl of capillary blood were used to make thin and thick blood smears respectively. The smears were stained with 2% Giemsa stain for 30 minutes and examined microscopically for malaria parasite. Venous blood was collected for the estimation of white blood cells count using Sysmex Automated Full blood count Analyzer. Of the 285 subjects examined, 178(62.5%) were infected with malaria. Subjects below 15 years of age had the highest prevalence rate of 26(78.8%) while subjects aged 49-59 years had the least prevalence of 7(50%). The mean (SD) WBC counts obtained in this study was 5.47 ± 1.080 (10 9 /l), while the mean (SD) malaria parasite densities were 256.99±394.271, 289.72±462.917 and 386.29±617.222 X 10 9 for absolute WBC count, Nigerian recommended WBC count and WHO recommended WBC count respectively. The difference in the mean malaria parasite density between Absolute WBC value and Nigerian accepted WBCs value was statistically significant (p=0.000). There was also a significant difference in the mean parasite density between Absolute WBC and WHO recommended WBC value (p=0.000). The difference in parasite densities obtained between Nigerian accepted WBC value and WHO recommended value was also significant (p=0.000). Overestimation of malaria parasite density can be reduced by using the corresponding individual’s WBC count to replace the 8.0x 10 9 /l WBC count set by WHO for the region. The corresponding WBC count should always be estimated when malaria parasite density is required to have a precise and accurate
malaria density.