Challenges of malaria diagnosis in paediatric patients at a Nigerian hospital
Errors in routine microscopy make it difficult to assess the performance of new malaria diagnostic tests in routine settings. This study compares the performance of routine malaria diagnostic tests, and explores the challenges of malaria diagnosis in paediatric patients in an endemic setting in South West Nigeria.
METHODS: The proportion of children classified as having malaria by clinical diagnosis, Rapid Diagnostic Test (RDT) and blood smear microscopy were compared. Test efficiency, the proportion of all tests that gave a correct result was determined relative to routine microscopy. Possible inaccuracies were explored
RESULTS: By clinical diagnosis 45.2% of children were diagnosed as having malaria, 37.6% tested positive to malaria parasite on RDT and 19.3% had positive blood smears on microscopy. Test efficiency of clinical diagnosis when compared to RDT and routine microscopy was 61.5% and 60.5% respectively. RDTs had a test efficiency of 80.7% when compared with routine microscopy. Based on expected malaria prevalence of 50.3% in South West Nigeria, clinical diagnosis of malaria was found to have a probability of a false positive/negative of 0.51 and 0.52 respectively. RDTs had a probability of a false positive result of 0.19 and a probability of a false negative result of 0.026.
CONCLUSIONS: With an expected malaria positivity of 50.3% for South west Nigeria, the true malaria morbidity among these paediatric patients remains questionable due to the differences in the results produced by the different diagnostic methods. The clinical implication of RDT-positive but microscopy-negative samples may be grave if microscopy results are erroneous. Quality control systems and surveillance of routine malaria diagnostics are imperative to limit misdiagnosis of malaria.