Comparison of various concentration methods used in parasitological examination of the stool samples

In Turkey, where the prevalence of parasitic infections is high, various laboratories use only Direct Wet Mount Preparation (DWMP) for the routine parasitological examination of the stool samples. Some concentration methods and a permanent stain such as trichrom are also recommended to be used beside this method which may be insufficient in distinguishing some of the protozoa trophozoites and in diagnosis of organisms that are rare in stool samples. In this study, stool samples of 404 patients applied to Celal Bayar University Hafsa Sultan Hospital Medical Parasitology Laboratory in July 2012-July 2013 were examined. DWMP and Trichrome Staining Method (TSM) were applied to all of the stool samples. Additionally, two different sedimentation methods including Formol-Ethyl Acetate Sedimentation Method (FEASM) and Modified Formol-Ethyl Acetate Sedimentation Method (MFEASM), and four flotation methods including Modified Zinc Sulphate Flotation Method (MZSFM), Saturated Salt Flotation Method (SSFM), Sugar Flotation Method (SFM) and Salt and Sugar Flotation Method (SASFM) were applied to stool samples in order to identify the most efficient concentration methods that can be applied under different conditions such as field and laboratory conditions. Intestinal protozoa were determined in totally 72 of 404 cases (17.8%) by at least one of these methods. These protozoa and the number of the patients were as follows: Blastocystis species 61 (15%), Giardia intestinalis 7 (1.7%), Entamoeba coli 2 (0.5%), Dientamoeba fragilis 1 (0.3%) and Iodamoeba butschlii 1 (0.3%). While all of the 72 cases diagnosed with protozoa infection were identified by TSM, positive results by DWMP were obtained in 68 cases. FEASM, one of the sedimentation methods, was positive in 66 of 72 protozoa, while MFEASM was positive in 70 cases. MFEASM which is found to be more easy to perform, faster and more efficient than FEASM may be recommended as a routine concentration method for the stool examination laboratories. Parasite was determined in 12 stool samples by MZSFM, 11 by SSFM, 10 by SFM and 11 by SASFM. The data we obtained suggested that SSFM may be used when MZSFM cannot be used, considering that zinc in MZSFM is more expensive. As a result, our data suggested that DWMP was useful in parasitological examination of stool samples; however, a concentration method and a permanent stain should also be performed for an accurate examination. A sedimentation method should be preferred preferably if a centrifuge is available. Otherwise, MZSFM or SSFM may be used as a concentration method. TSM, especially Wheatley modification, was found to be very successful in the diagnosis and differentiation of the intestinal protozoa. Keywords: Concentration methods, sedimentation methods, flotation methods, stool examination.