Comparison of four rapid diagnostic tests, ELISA, microscopy and PCR for the detection of Giardia lamblia, Cryptosporidium spp. and Entamoeba histolytica in feces

•We examine four rapid diagnostic tests for Giardia, Cryptosporidium and Entamoeba.•Sensitivities are good for Cryptosporidium and E. histolytica, variable for Giardia.•Specificities are excellent for G. lamblia and Cryptosporidium.•Differentiation between E. histolytica/dispar by PCR remains necessary.•When microscopic expertise is poor, this can be a valuable tool to replace microscopy.

PurposeMicroscopy is the diagnostic reference standard for the detection of parasites, but it is labor-intensive and requires experience. Rapid diagnostic tests (RDTs) can provide an alternative to microscopy.MethodsRDTs from four different manufacturers were compared to enzyme-linked immunosorbent assay (ELISA), microscopy and/or parasite-specific real-time PCR: ImmunoCardSTAT!®CGE (Meridian Bioscience Inc., Cincinnati, Ohio, USA) (A), Crypto/Giardia Duo-Strip (Coris Bioconcepts, Gembloux, Belgium) (B), RIDA®QUICK Cryptosporidium/Giardia/Entamoeba Combi (R-BioPharm, Darmstadt, Germany) (C) and Giardia/Cryptosporidium Quik Chek (Techlab Inc., Blacksburg, Virginia, USA) (D).ResultsThirty frozen samples were analyzed retrospectively. For Giardia lamblia (n = 12) and Cryptosporidium (n = 12) sensitivities ranged from 58% (B), over 83% (A, C) to 100% (D) and from 92% (B) to 100% (A, C, D), respectively. Specificity for both G. lamblia and Cryptosporidium was 100% for all RDT brands. Sensitivity for Entamoeba histolytica (n = 5) was 100%, while specificity reached 80% (A) to 88% (C). In a prospective study, fresh samples were tested. For G. lamblia (n = 30), sensitivity ranged from 66% (B), over 79% (A) and 83% (C) to 100% (D) and specificity varied between 94% (D) and 100% (A, B, C). For Cryptosporidium (n = 3), sensitivity was 100% for all brands except (B) (67%) and specificities were 95% (A, B), 98% (C) and 100% (D). E. histolytica (n = 1) was detected by both (A) and (C), while specificity was 81% and 87% respectively.ConclusionRDTs can be a valuable tool when microscopic expertise is poor and in remote and outbreak settings where other techniques are often not available and rapid diagnosis is required.