Comparison And Evaluation Of The Three Detection Methods Of G6pd Deficiency

Objective: To compare and evaluate the common locally available spectrophotometric enzyme assay methods, the NBT and methemoglobin reduction test (M-Hb) methods to the internationally recommended WHO-37 method in the detection of glucose-6-phosphate dehydrogenase (G6PD) deficiency. Method: 243 Venous blood samples randomly selected from those sent to the laboratory for routine G6PD enzyme assay were each assayed by the three methods. Results got by the two local methods were then compared to those of the WHO-37 method for concordance, accuracy, sensitivity and specificity. For the NBT and WHO-37 methods, a graph of the relationship between absorbance and enzyme activity was compared for different levels of enzyme activities. The detection rate for female heterozygotes by the 3 methods were also compared. Results: Both the NBT and M-Hb methods have a medium to good concordance to the WHO-37. The NBT method however has a better crude accuracy (79.01% to 69.14%) and a higher K value (0.66 to 0.52) to WHO-37 than the M-Hb method. The NBT method particularly has an excellent concordance (K=0.81) and high sensitivity (98.3%) in detection of deficient enzyme activity and also high accuracy for detection normal activity (95.4%). The M-Hb method in detection of deficient activity has a medium to good concordance (K=0.65) and sensitivity of 87.9%. Both methods only have medium concordance to theWHO-37 in detection of intermediate enzyme activity; for NBT method K=0.47, sensitivity 45.7%, M-Hb method K=0.46, sensitivity 65.7%. There was a poor direct relationship in the graph of absorbance verse enzyme activity especially for hemolysate with intermediate enzyme activity for the NBT method as compared to the WHO-37, which may explain the low concordance of the NBT to the WHO-37 in detection of intermediate enzyme activity. Conclusions: We found that the NBT method has a good concordance to the WHO-37 method and is suitable for detection of normal and deficient enzyme activities but not reliable in detection of intermediate enzyme activity, because of the poor direct relationship in the graph of absorbance verses enzyme activity for hemolysates with intermediate enzyme activity. The NBT method being more economical, requiring just a simple spectrophotometer and less expensive reagents and locally available in lower hospitals is basically suitable for clinical and laboratory purposes.