Hematology Lessons Best Lab: Glucose-6-Phosphate Dehydrogenase Qualitative Screening

Glucose-6-Phosphate Dehydrogenase (G6PDH) Qualitative Screening

BackGround Information

G-6-PDH deficiency in RBCs have been demonstrated to be the basis for certain drug-induced
haemolytic anaemias. Hence, Severe haemolytic anaemia may result in these individuals when they are given many commonly used drugs.This emphasized the importance of identifying individuals with this biochemical defect as an aid in the selection of therapeutic agents.  The majority of
patients who have demonstrated G-6-PDH deficiency are clinically normal until exposed to one of
several oxidant drugs (anti-malarial drugs, sulfa drugs, ascorbic acid and others).

This defect should be considered whenever an otherwise unexplained case of haemolytic anaemia is

Red cell G-6-PDH deficiency has been found in about 13% of African-American males and in
about 3% of African-American females. The incidence is also high among other racial and ethnic
groups, such as Sardinians, Greeks and Sephardic Jews.

Principle of Fluorescence-Based Test Kit

For semi-quantitative purposes, the highly suggested method is to
estimate G6PDH in terms of visual appearance of fluorescence in red cell
substrate mixtures. Many diagnostic kits in the commercial market
involves the reaction:


  1. Whole blood is usually collected with EDTA, heparin or acidcitratedextrose.
  2. Incubate a small amount of blood with glucose-6-phosphate and nicotinamide adenine dinucleotide phosphate (NADP). 
  3. Drops of the mixture are removed at 5-minute intervals, spotted on filter paper 
  4. Viewed under long-wave ultraviolet light in a viewing box or a darkened room

* Fluorescence is clearly evident in mixtures prepared from normal blood, whereas deficient
samples yield little or no fluorescence.

Expected Results

  • Normal sample: demonstrate moderate to strong fluorescence after 5 minutes, and strong fluorescence after 10 minutes.
  • Intermediate level sample: demonstrate weak fluorescence after 5 minutes and
  • Moderate level sample: fluorescence after 10 minutes.
  • Deficient Level Sample: very faint or no fluorescence even after 10 minutes

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