QUESTION: What is the best lab for me to run to test G6PD before I administer HDIVC?
ANSWER: G6PD testing is complex but the basics are as follows:
If you have a negative test of any of the three kinds you are free to proceed with oxidative therapies.
The three test modalities are:
1. Qualitative (“Normal / Abnormal”)
2. RBC-G6PD or Total-G6PD
3. Quantitative G6PD [i.e. Lab Corp code – 001917]
* A “Quant” G6PD is a calculated value using both Total and RBC G6PD – considered most sensitive at assessing borderline cases. G6PD QUANT = {G6PD Blood / RBC G6PD} Value given in Units per Trillion RBC (U/Tril RBC)
If you have a positive test however the most sensitive (as there are many false positives in #1&2 above) you are best to use the Quantitative G6PD to find out if it is a “true” positive. If the “Quant” (#3) is low then you truly cannot proceed with oxidative therapies. As a note if it is a low result occasionally that can be functional (post chemo or radiation, nutrient deficient etc) so we will often run 2-4 weeks of IV Nutrients with glutathione and re check the Quant – sometimes we see the Quant rise to normal. If it is still low it is likely a true genetic issue and they just have to avoid oxidation.
Best reference for the sensitivity of G6PD testing from which I derived this guideline is Am. J. Trop. Med. Hyg.,91(4), 2014, pp. 854–861