The predictive value of syndromic approach to diagnosis of malaria among adults attending the outpatient clinic of a tertiary hospital in Ikeja, Lagos

Abstract

Background: Malaria is a major cause of morbidity and mortality in Nigeria-a country known for high prevalence of malaria. Available records show that ≥ 50% of the population of the country suffers from at least one episode of malaria each year. In all settings, ideally clinical suspicion of malaria should be confirmed with a parasitological diagnosis. However, in settings where parasitological diagnosis is not possible, the use of detailed weighting and scoring systems for clinical symptoms and signs of malaria may improve the accuracy of clinical diagnosis. This study evaluated the complementary role of a syndromic approach to the diagnosis of malaria with the use of a structured algorithm as a tool to improve upon the presumptive diagnosis of malaria.

Methods: A hospital based descriptive cross-sectional study was done. Participants were selected using a systematic sampling method. A total of 386 adult participants with subjective experience of fever who had presumptive diagnosis of malaria were studied. Common presenting symptoms and signs were evaluated for those associated with positive malaria microscopy in order to determine their utility in syndromic diagnosis of malaria. The clinical predictors of malaria were determined by the logistic regression model. The level of statistical significance was set at p ≤ 0.05. Sensitivity, specificity, and predictive values were calculated for the various clinical predictors and the algorithm score.

Results: The data of 386 participants who presented with complaint of fever were analysed. There were 49.48% male and 50.52% female respondents. The respondents aged 31-40 years were in the majority (44.82%). The prevalence of malaria as indicated by positive malaria microscopy was 71.76%. The clinical features significantly associated with positive malaria microscopy in the bivariate analysis were joint pains, reduced appetite, and normal chest examination, however, following logistic regression, reduced appetite (OR 1.65; 95% CI: 1.04- 2.64, p value = 0.035) and normal chest examination (OR 3.07; 95% C.I: 1.41-6.70, p value= 0.005) were features found to be significant. Syndromic positivity for malaria assigned to total scores >7, had a sensitivity of 97.5%, specificity of 7.3%, positive predictive value of 72.8%, and negative predictive value of 53.3%.

Conclusion: A total score > 7 as syndromic positivity for malaria in this study had a very high sensitivity (97.5%) but low specificity (7.3%) for malaria infection. A respondent with a history of fever who had been presumed to have malaria, and has a total score > 7, is three times more likely to have malaria infection. Such patient should be treated for malaria in settings with no facility for parasitological diagnosis. However, on account of the low specificity of this syndromic approach, it is important for clinicians to examine patients properly to rule out other causes of fever such as urinary tract infection, gastrointestinal infection.

Keywords: Syndrome, Malaria, Adult, Outpatient, Hospital