Use of micro samples of finger prick blood dried on filter paper for a quick and simple dipstick dot-EIA for diagnosis of amebic liver abscess (ALA)

Abstract

Filter paper was used as a support to absorb micro samples of finger prick blood for detection of antibodies to Entamoeba histolytica (causative organism of amebiasis) by a rapid dipstick dot-EIA technique; 8 μl of blood was sufficient to saturate discs (diameter 6 mm) of Whatman paper No. 3. Conditions of elution of blood from the discs were optimized and the best results were obtained when 0.4 ml of buffer was used for elution for 30 minutes at room temperature. The filter paper technique is extremely useful for field use and for diagnosis of amebic liver abscess on a large scale since it does not involve centrifugation of blood and use of sterile vials because blood dried on paper can be stored in polythene bags at room temperature for up to 3 months and for a week at 42°C without significant loss of antibody activity, thereby eliminating the need of refrigeration of samples for storage or transportation to a reference laboratory. Elution of blood from different discs of the same patient was found to be highly reproducible without appreciable loss of sensitivity or specificity. Twenty-four confirmed ALA, 29 non-ALA, and 25 apparently normal healthy controls, with no previous history of amebiasis, were tested. Sensitivity and specificity of the test was found to be 96% and 92%, respectively.