Assessment of the Indirect Immunofluorescence Antigen Test and Formol-Ether Concentration Technique in the Diagnosis of Schistosoma Mansoni at Lancet

Abstract

Schistosomiasis, caused by the Schistosoma mansoni parasite, is a neglected tropical disease with a significant burden in Zimbabwe. Accurate diagnosis is crucial for effective treatment and control strategies. This study aimed to compare the diagnostic performance and cost- effectiveness of the Indirect Immunofluorescent Antibody Test (IFAT) and the Formol-Ether Concentration (FEC) technique for detecting Schistosoma mansoni infections at Lancet Clinical Laboratories in Zimbabwe. A retrospective cross-sectional study was conducted using laboratory records from Lancet Clinical Laboratories in Harare, Zimbabwe from October 2022 to March 2023. Data on IFAT and FEC test results, along with demographic and clinical information, were collected for individuals suspected of Schistosoma mansoni infection. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and diagnostic accuracy were calculated for both techniques. McNemar's test was used to assess the discordance between IFAT and FEC results. Cost-effectiveness was evaluated by calculating the incremental cost- effectiveness ratio (ICER). Turnaround time (TAT) was evaluated by calculating the average TAT and determining the laboratory workload and workflow of FEC and IFAT. The study had total of 105 samples that were tested with IFAT and FEC method. FEC, the sensitivity was 39.5%, specificity was 100%, PPV was 100%, NPV was 70.4%, and diagnostic accuracy was 75.2% accordingly. While with IFAT, the sensitivity was 100%, specificity was 96.8%, PPV was 95.6%, NPV was 100%, and diagnostic accuracy was 98.1% accordingly. McNemar's test showed there is a significant discordance between the two techniques( pa + pb≠pa + pc and p- value < 0.05 significance level). This means there is a substantial difference in the performance of the two diagnostic methods FEC and IFAT. However, the significant discordance between the two techniques highlighted the need for accurate and sensitive diagnostic methods, like IFAT. Next was the cost-effectiveness analysis that showed the IFAT method had an incremental cost- effectiveness ratio (ICER) of 0.38 US dollars per additional case detected compared to FEC, suggesting that IFAT, though its more expensive, is a cost-effective option for Schistosoma mansoni diagnosis. Lastly the turnaround time analysis showed that the average TAT 1hour 38minutes for FEC and 36 hours 30minutes along with the workload and workflow of both methods were acceptable. Overall, IFAT demonstrated a superior diagnostic performance compared to FEC, with higher sensitivity and diagnostic accuracy in detecting Schistosoma mansoni infections though being expensive and having a longer TAT. FEC was seen to be more cost-effective than IFAT and time effective. The findings of this study provide valuable insights into the performance, cost-effectiveness, and operational considerations of IFAT and FEC techniques for Schistosoma mansoni diagnosis in Zimbabwe, informing decision-making and quality improvement initiatives in healthcare.