High Specificity but Low Sensitivity of Lab-on-a-Disk Technique in Detecting Soil-Transmitted Helminth Eggs among Pre- and School-Aged Children in North-Western Tanzania

Abstract

An estimated 1.5 billion people are infected with soil-transmitted helminths (hookworms, Ascaris lumbricoides and Trichuris trichiura). These infections are targeted for elimination by the World Health Organization (WHO) by 2030, with the main interventions being mass drug administration using albendazole or mebendazole. Tanzania is one of the endemic countries; it has been implementing MDA to school-aged children for more than a decade and the infection prevalence and intensity of infection have declined. Thus, at this point, the monitoring and evaluation of infection prevalence and intensity of infections, and assessing drug efficacy is crucial and requires accurate diagnostic tests. The currently used standard diagnostic test, the Kato–Katz (KK) technique, has several limitations and the WHO is calling for the development and evaluation of new diagnostic tests. The Lab-on-a-disk (LOD) was developed and tested in the endemic areas of north-western Tanzania to evaluate its sensitivity and specificity using KK and the formol-ether concentration technique. The results showed that when using a duplicate KK slide, the LOD had a sensitivity and specificity of 37.2% (95% CI: 30.7–43.9) and 67.3% (95% CI: 63.1–71.3%). Using four KK slides as a standard technique, the overall sensitivity and specificity were 37.7% (95% CI: 33.1–42.6) and 70.7% (95% CI: 65.5–75.6). The LOD attained high specificity but low sensitivity especially in detecting eggs of Trichuris trichiura. The LOD technique has potential as a promising diagnostic test, but its sensitivity still requires improvement.

Keywords

• soil-transmitted helminths
• diagnosis
• sensitivity
• specificity
• Lab-on-a-disk
• Tanzania