Page 106 - Invited Paper Session (IPS) - Volume 2

IPS186 Fagbamigbe, A. F.
On the discriminatory and predictive accuracy of
RDT against the microscopy smear tests in the
diagnosis of malaria among under-five children
in Nigeria
Fagbamigbe, A. F.

Abstract
Accurate identification of malaria cases is very crucial to the management of
cases and to the success of malaria eradication agenda. This study is designed
to evaluate the discriminatory and predictive accuracy of Malaria Rapid
Diagnostic Tests (RDTs) in Nigeria. The data obtained during the 2015 Nigeria
Malaria Indicator Survey was used to quantify the discriminatory accuracy
through the analysis of its sensitivity, specificity, positive (LR+) and negative
(LR-) likelihood ratio. The positive (PPV), and negative (NPV) predictive values,
area under the receiver operating characteristic curve, and diagnostic odds
ratio were used to assess the predictive accuracy of the RDTs using expert
microscopy as a gold standard at p=0.05. The McNemar paired test and the
Kappa statistics were used to assess agreement between the diagnostic tests.
There was a significant but not an excellent agreement between the results of
the RDT and microscopy tests (p<0.001). The overall sensitivity of the RDT was
87.6%(85.9%-89.2%), specificity was 75.8%(74.4-77.1%) while the diagnostic
accuracy stood at 79.0%(77.9%-80.0%). The LR+, LR-, PPV and NPV were
3.6(3.4-3.8) and 0.16(0.14-0.19), 57.5%(56.1%-58.9%) and 94.2%(93.5%-94.9%)
respectively. The sensitivity of RDT increased as the age of the children
increased, from 85.7% among those aged 0-6 months to 86.1% in 7-23 month
olds to 88.1% among those aged 24-59 months but the reverse was the
specificity. For children with severe anaemia, the sensitivity of the RDT was
nearly 100% compared with a specificity of 39%. While the sensitivity and the
PPV reduced with children’s level of anaemia, the higher the severity of
anaemia the lower the NPV, specificity, the diagnostic accuracy of the RDT.
The odds of RDT been sensitive was about 50% (aOR=0.52(95% CI: 0.30-0.90))
lower among children aged 7-23 months compared with those aged 24-59
months while the odds of RDT been sensitive was 2 times (aOR=2.15 (95%
CI:1.67-2.77)) higher among those 7-23 months than among those aged 24-
59 months. Although there was a significant agreement in the outcomes of
RDT and Microscopy tests, the discriminatory accuracy of RDT was weak. Also,
the predictive accuracy, especially the PPV of the RDTS, were very low. These
measures of accuracies differed across the age of the children, level of
anaemia, and other characteristics. Without an accurate, efficient and reliable
diagnosis of malaria, the goal of eliminating malaria and reduction of malaria-
related deaths to zero by 2020 will only be a wide chase.

93 | I S I W S C 2 0 1 9