Performance of rapid DiaMed OptiMal-IT^® malaria test in an endemic Ghanaian setting

At peripheral health facility levels, the diagnosis of malaria is difficult due to lack of infrastructure. In the study reported here, the diagnostic performance of a batch of 'DiaMed OptiMAL-IT' (Cressier, Switzerland) rapid antigen tests were examined in parallel with routine microscopy for a select population of high risk individuals: 202 pregnant women and 200 children less than 5 years old in an endemic setting in Ghana. Results of both diagnostic methods were compared to that of cross-checking microscopy, taken as gold standard, at the Navrongo Health Research Centre. Of the 402 patients, 218 (54.2%) were confirmed with Plasmodium falciparum infections by cross-checking. All 218 patients (100%) were accurately diagnosed with malaria by routine microscopy. Of these, 151 (69.3%) were positive by DiaMed OptiMAL-IT test (26 false positives, 67 false negatives). DiaMed OptiMAL-IT had the following performance indicators for detection of P. falciparum among pregnant women and children less than 5 years respectively: Sensitivity-50.5% [95% CI (40.6-60.3)], 87.7% [95% CI (78.7-92.1)]; Specificity-82.5% [95% CI (73.1-89.1)], 89.6% [95% CI (80.8-94.8)]; Predictive values for positive tests-75.7% [95% CI (63.7-84.8)], 91.6% [95% CI(85.2-95.8%)]; Predictive values for negative tests-60.6% [95% CI (51.7-68.9)], 83.8% [95% CI (74.5-90.3)]; Likelihood ratio for positive tests-2.88, 10.8; Likelihood ratio for negative tests-0.59, 0.19; Cohens Kappa values-0.33 [95% CI (0.20-0.43), 0.76 [95% CI (0.65-0.83)]. Our results suggest that DiaMed OptiMAL-IT tests should not replace microscopy in our endemic setting.