Comparison of Ritchie and Kato-Katz methods for the detection of intestinal helminths in humans: a systematic review and meta-analysis

BACKGROUND: Comparative evidence on the diagnostic performance of Formalin-Ether Concentration (FEC) versus the Kato-Katz thick smear (KK) for detecting intestinal helminths in humans remains inconsistent. This systematic review and meta-analysis compared the odds of detecting intestinal helminths using FEC versus the single-slide KK.

METHODS: A systematic search was conducted across six databases (PubMed, Scopus, EMBASE, Web of Science, Nursing and Allied Health Premium, and Ovid). Eligible studies directly compared FEC with single-slide KK for stool examination. Data was extracted using a standardized template, and risk of bias was assessed using the Joanna Briggs Institute (JBI) tools. Pooled odds ratios (ORs) were estimated using fixed-effect and random-effects models. Heterogeneity (I 2), subgroup analyses, meta-regression, and assessments of publication bias (funnel plots, Harbord tests, and trim-and-fill) were performed where appropriate.

RESULTS: A total of 40 studies met the inclusion criteria. For overall intestinal helminths (27 studies; 11,198 samples), the random-effects model produced a nonsignificant pooled OR of 0.76 (95% confidence interval [CI]: 0.55-1.05, I 2  = 94.2%), whereas the fixed-effect model indicated higher detection by KK (OR = 0.84; 95% CI 0.78-0.91). For soil-transmitted helminth infections (STHs) (12 studies; 3615 samples), pooled estimates were 0.98 (95% CI 0.61-1.55, I 2  = 71.3%; random-effects) and 0.84 (95% CI 0.74-0.97; fixed-effect). Species-specific pooled ORs were nonsignificant for hookworm (0.75; 95% CI 0.48-1.18, I 2  = 83.2%), Ascaris lumbricoides (0.94; 95% CI 0.63-1.40, I 2  = 80.8%), and Trichuris trichiura (0.65; 95% CI 0.40-1.07, I 2  = 68.2%). FEC detected Strongyloides stercoralis significantly more frequently (OR = 5.02; 95% CI 1.75-14.41, I 2  = 0%), while KK detected Schistosoma mansoni more often (OR = 0.59; 95% CI 0.39-0.90, I 2  = 93.7%). For Opisthorchis viverrini, no difference was observed between the two detection methods (OR = 1.09; 95% CI 0.61-1.92, I 2  = 86.7%). Subgroup analyses revealed notable regional and species-level variation. Meta-regression indicated minimal influence of study design, continent, or participant type. Publication bias assessments suggested minimal small-study effects.

CONCLUSIONS: The diagnostic performance varied substantially between FEC methods and KK, depending on helminth species, region, and study design. KK was more sensitive at detecting S. mansoni and often performed similarly to or better than other methods for STHs, particularly in low-intensity settings. In contrast, FEC methods showed superior detection of S. stercoralis and preserved hookworm eggs. These findings support the use of integrated diagnostic strategies that combine KK with sedimentation or molecular methods to enhance surveillance in the era of helminth control and elimination.