IMPROVED PROTOCOL OF ISOPROPANOL PRECIPITATION TEST FOR HEMOGLOBIN E SCREEN

Abstract

Isopropanol precipitation test is the test established to screen for hemoglobin E (HbE). This test was tedious, requiring several steps to complete the protocol. This study was aimed to improve the protocol of isopropanol precipitation test so that it can simply and accurately screen for HbE. The incubation time, percentage of isopropanol, hemolysate preparing method, and volume of working isopropanol were re-optimized. The effect of hematocrit as well as the stability of the reagent and of the EDTA blood were also determined. The improved isopropanol precipitation test was found to work well with adding 50 mL hemolysate; prepared by mixing whole EDTA blood in 0.05% Triton-X 100, into 500 mL of 19% (v/v) isopropanol in 0.1 M Tris-HCl, pH 7.4 and incubated at 37oC for 20 min. This improved test was as effective as the traditional dichlorophenol indolphenol precipitation test and stable for at least 2 months at both 4oC and 30oC. The EDTA blood could be stored at 4oC for one month with no effect on test results. We concluded that this improved isopropanol precipitation test was effective and, coupling with the very low investing cost, could be the new choice for HbE screen.