Comparing the efficiency of four diagnostic concentration techniques performed on the same group of intestinal parasites

Abstract

Background: Intestinal parasites are a major public health problem, and their accurate diagnosis is important. The purpose of this study was to evaluate and compare the efficiency of four concentration techniques for the detection of intestinal parasites under laboratory conditions.

Methods: A total of 800 suspension specimens including 200 samples for each technique were simultaneously and parallel processed for comparing the diagnostic efficiency of the formalin-tween (FTC), formalin-ether (FEC), formalin-acetone (FAC), and formalin-gasoline concentration (FGC) techniques.

Results: Sensitivity of FTC, FEC, FAC, and FGC techniques for diagnosis of intestinal parasites was 71.7%, 55.8%, 70.0% and 56.7%; and their negative predictive values (NPV) were 70.2%, 60.2%, 69.0% and 60.6%, respectively. FTC and FAC techniques with equivalent recovery rates were significantly more sensitive than FEC and FGC techniques for diagnosing helminth ova, but for diagnosis of protozoan cysts they were reversed. Overall diagnostic k agreement for FTC and FAC techniques was substantial, while for FEC and FGC techniques it was moderate. The k statistic indicated low to moderate agreement for diagnosis of helminths and moderate to substantial agreement for protozoa.

Conclusion: Tween, acetone and gasoline reagents are more stable, safer, less flammable and of lower cost than that of ether; and promise to be a useful alternative to ether- concentration. Our results demonstrated that the combined use of parasitological techniques is important for the diagnosis of all intestinal parasites. FTC and FGC techniques are superior for the diagnosis of helminth ova and protozoan cysts in stool, respectively. Additional studies are suggested, using a larger sample size and different parasites in the field.

Keywords: Concentration technique, Diagnosis, Intestinal parasite, Sensitivity, NPV, FAC, FTC, FEC, FGC