Comparison of real-time PCR and the Kato-Katz method for the diagnosis of soil-transmitted helminthiasis and assessment of cure in a randomized controlled trial

Abstract

Background 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. Results Two 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. Conclusions In 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).

Evaluation of the Allplex™ GI-Helminth(I) Assay, the first marketed multiplex PCR for helminth diagnosis

“…For each parasite targeted, we compared our results to those in the literature ( Table 3 ) [ 3 , 5 , 10 , 13 , 15 , 17 , 18 , 20 , 25 ]. Overall, the performances of the Allplex™ GIPH assay were similar to other PCR techniques, except for hookworm and T. trichiura detection, the latter being improved when applying bead-beating pretreatment.…”

“…The rates of false-negative results for S. stercoralis detection were variable, as they ranged from 12% to 50%, but this was mainly reported in old studies using S. stercoralis PCRs with poor performances [ 5 , 6 , 25 ]. It should be noted that in many comparisons of PCR to microscopy, egg detection relied on the Kato-Katz method [ 3 , 5 , 13 , 15 ]. In our study, eggs were mostly detected using the merthiolate-iodine-formalin concentration method, which is known to be more sensitive as it uses a higher amount of sample [ 12 ].…”

Preclinical and Clinical Characteristics of the Trichuricidal Drug Oxantel Pamoate and Clinical Development Plans: A Review

“…It is likely that differences in infection intensity, as well as the different diagnostic methods used in the different studies (e.g. Kato Katz, formol-ether, Stoll) have an impact on the observed cure rates (CRs) and egg reduction rates (ERRs) [ 19 , 20 ].…”

The role of diagnostic technologies to measure progress toward WHO 2030 targets for soil-transmitted helminth control programs

“…There is a lot of controversy around the performance of the KK procedure, and often the lack of sensitivity, reproducibility, and error-prone manual readout are considered major shortcomings [14]. Surprisingly enough, specificity of KK has not been seen as a drawback, while it is exactly that performance requirement that is crucial in low prevalence and elimination settings [3].…”