Which semi-quantitative tests are performed in the workup of glucose-6-phosphate dehydrogenase (G6PD) deficiency?

Updated: Jun 25, 2020
  • Author: Lawrence C Wolfe, MD; Chief Editor: George T Griffing, MD  more...
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Answer

Semi-quantitative tests:

  • Fluorescent spot test: This is a direct test that measures the generation of reduced nicotinamide adenine dinucleotide phosphate (NADPH) from nicotinamide adenine dinucleotide phosphate (NADP+); the test is positive if the blood spot fails to show fluorescence under ultraviolet light. It is rapid, simple, sensitive, and inexpensive. [6, 7, 8]  A variant of the spot test that can be interpreted by simple color change with naked eye examination is used for screening large populations in tropical areas and before starting treatment with antimalarial drugs, such as primaquine, in countries where G6PD deficiency and malaria are both endemic. The test is not reliable in heterozygous females.
  • Methemoglobin reduction test: This is a rapid indirect test that measures the reduced methemoglobin levels produced after NADPH oxidation. G6PD activity is assessed by first treating red blood cells with nitrite (converting oxyhemoglobin [red] to methemoglobin [brown]), and then examining the rate of NADPH-dependent methemoglobin reduction in the presence of an appropriate redox catalyst (Nile blue or methylene blue) and substrate (glucose). [6]
  • Cytofluorimetric method: This is a cytochemical typing assay that provides a fluorometric readout of the classic methemoglobin reduction test at the level of an individual red blood cell. This assay represents a useful addition to the screening and research toolkit for G6PD deficiency, especially in malaria-endemic areas. [7]

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