Abstract
BackgroundDiagnosis of soil-transmitted helminths (STHs) in developing countries is commonly based on microscopic detection of eggs in stool samples, using the Kato-Katz (KK) method, which has a poor sensitivity for detecting light intensity infections. We compared the performance of the KK method and real-time PCR in the framework of a randomized trial, which evaluated four novel treatments against Trichuris trichiura and concomitant STH infections.ResultsTwo stool samples obtained from 320 participants were examined at baseline and follow-up with quadruplicate KK and PCR analyses of one of the two samples using “bead-beating” for DNA extraction. At follow-up, 80 samples were negative according to both PCR and KK and 173 were positive with both methods for any of the STHs. Relative to PCR, the calculated sensitivity of KK at follow-up was 83.6%, 43.0% and 53.8% for T. trichiura, for hookworm and for Ascaris lumbricoides, respectively. The sensitivity of PCR compared with KK at this time point was 89.1% for T. trichiura, 72.7% for hookworm and 87.5% for A. lumbricoides. Cure rates (CRs) for T. trichiura and A. lumbricoides were slightly lower with the PCR method. For hookworm CRs with KK were mostly significantly lower, namely 36.7%, 91.1%, 72.2% and 77.8% for moxidectin, moxidectin in combination with tribendimidine, moxidectin in combination with albendazole and albendazole in combination with oxantel pamoate, respectively, whereas with PCR the CRs were 8.3%, 82.6%, 37.1% and 57.1%, respectively.ConclusionsIn conclusion, a single real-time PCR is as sensitive as quadruplicate KK for T. trichiura and A. lumbricoides detection but more sensitive for hookworm, which has an influence on the estimated treatment efficacy. PCR method with DNA extraction using the “bead-beating protocol” should be further promoted in endemic areas and laboratories that can afford the needed equipment.The study is registered at ISRCTN (no. 20398469).
Highlights
Diagnosis of soil-transmitted helminths (STHs) in developing countries is commonly based on microscopic detection of eggs in stool samples, using the Kato-Katz (KK) method, which has a poor sensitivity for detecting light intensity infections
Cure rates for T. trichiura and A. lumbricoides were slightly lower with the polymerase chain reaction (PCR) method than with the KK method, these differences were not statistically significant
Our results show that a single PCR, based on the beadbeating extraction method, is as sensitive as quadruplicate KK for T. trichiura and A. lumbricoides detection but more sensitive than quadruplicate KK for hookworm, which is evident after treatment
Summary
Diagnosis of soil-transmitted helminths (STHs) in developing countries is commonly based on microscopic detection of eggs in stool samples, using the Kato-Katz (KK) method, which has a poor sensitivity for detecting light intensity infections. We compared the performance of the KK method and real-time PCR in the framework of a randomized trial, which evaluated four novel treatments against Trichuris trichiura and concomitant STH infections. The soil-transmitted helminths (STHs) Trichuris trichiura, Ascaris lumbricoides and the hookworms (Ancylostoma duodenale and Necator americanus) infect an estimated 1.5 billion people mostly in tropical and subtropical countries [1]. Diagnosis of STH is usually based on microscopic detection of STH eggs in stool samples, with Kato-Katz being the most widely used method in human parasitology [5, 6]. No quality control can be conducted in the diagnosis of hookworm eggs, since these are no more detectable after a couple of hours from sampleprocessing [7, 8]
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