Comparison of stool examination techniques to detect Opisthorchis viverrini in low intensity infection

Opisthorchiasis, caused by Opisthorchis viverrini, remains the public health significance in Thailand, particularly in the northeastern region. Number of parasitological techniques is available for diagnosis. However, the detection the parasite's eggs in stool still referred as gold standard. Today, most people living in the endemic areas harbored the light infection. In this study, we compared the performance of formalin-ethyl acetate concentration technique (FECT), Kato-Katz technique, fecal parasite concentrator kit (FPCK) and direct simple smear technique for O. viverrini egg examination in stool. The results revealed that the FECT gave the best sensitivity (91.0%) followed by Kato-Katz technique, FPCK and direct simple smear techniques. Interestingly, the FECT showed the highest sensitivity in both groups of egg per gram (EPG) <50 (94.3%) and EPG ≥ 50 (100%). The FPCK and direct simple smear technique exhibited the higher sensitivity in EPG ≥ 50 group compared with EPG < 50 group (p <  0.05). However, the sensitivity of FPCK was not statistically differed from that direct simple smear in EPG <50 and EPG ≥50 group. In conclusion, the FECT showed the highest efficiency to detect O. viverrini egg in stool, followed by Kato-Katz technique, FPCK and direct simple smear technique. Substituting FPCK (Mini Parasep® Kit) for FECT and Kato-Katz method is not recommended for low intensity infection.