Comparison between Quantitative Polymerase Chain Reaction and Sodium Nitrate Flotation Microscopy in Diagnosing Soil-Transmitted Helminth Infections

Adam W. Bartlett, Rebecca Traub, Salvador Amaral, Sze Fui Hii, Naomi E. Clarke, Alexander Matthews, Patsy A. Zendejas-Heredia, Paul Arkell, Merita Antonia Armindo Monteiro, Virginia da Conceicao, Carolina da Costa Maia, Maria Imaculada Soares, Josefina D. Prisca Guterres, Joshua R. Francis, Susana Vaz Nery

There is evolving interest in alternate microscopy techniques and quantitative polymerase chain reaction (qPCR) to evaluate soil-transmitted helminth (STH) burden. Using data from a cross-sectional survey of 540 schoolchildren across six primary schools in three municipalities of Timor-Leste, we compared the performance of microscopy using sodium nitrate flotation (SNF) and qPCR in determining STH prevalence and infection intensity. Prevalence by qPCR was higher than SNF for Ascaris lumbricoides (17.5% versus 11.2%), hookworm (8.3% versus 1.2%), and Trichuris trichiura (4.7% versus 1.6%). Agreement between SNF and qPCR was fair for hookworm (κ = 0.21) and moderate for A. lumbricoides (κ = 0.59) and T. trichiura (κ = 0.44). Moderate or heavy intensity infections were identified in 15.9% of infections detected by SNF, whereas qPCR identified 36.1% as moderate or heavy infections using cycle threshold to eggs per gram conversion formulas. Quantitative PCR is a promising diagnostic technique, though further studies validating infection intensity correlates are required.