Evaluation of the blue formazan spot test for screening glucose 6 phosphate dehydrogenase deficiency

Several screening tests for glucose 6 phosphate dehydrogenase (G6PD) defici ency have been reported thus far, and a standardized method of testing was proposed by the International Council for Standardization in Hematology (IC SH). The screening test used in any particular laboratory depends upon a nu mber of factors such as cost, time required, temperature, humidity, and ava ilability of reagents. In this study, a direct comparison between three dif ferent G6PD screening methods has been undertaken. In 71 cases (50 hematolo gically normal volunteers, 9 hemizygous G6PD-deficient males, and 12 hetero zygous deficient females), the blue formazan spot test (BFST) was compared with the conventional methemoglobin reduction test (HiRT) and the ICSH-reco mmended fluorescent spot test (FST-ICSH). In all cases, the results obtaine d with the three screening tests were correlated with the enzyme activity a ssayed spectrophotometrically. In hemizygous G6PD-deficient males, all case s were equally detected with the three methods: BFST (4.7-6.64, controls: 1 1.1-13.4), BMRT (score +3 in all 9 cases), and FST (no fluorescence in 9 ca ses). In heterozygous G6PD-deficient females, two methods detected 7 out of 12 cases (BFST: 8.71-11.75, controls: 11.1-13.4; and BMRT: score +3 in 7 c ases), whereas the FST-ICSH missed all 12 cases that presented a variable d egree of fluorescence, Although the sensitivity for G6PD-deficient carrier detection is the same fur the BMRT and the BFST, the latter has the advanta ge of being semiquantitative and not merely qualitative. Unfortunately, non e of the three screening tests compared here allowed the detection of the 1 00% heterozygote carrier state of G6PD deficiency. (C) 1999 The Japanese So ciety of Hematology.