How to order a Glucose-6-Phosphate Dehydrogenase (G6PD) test?

From the Guidelines

To order a G6PD test, you should first consult with a healthcare provider who can generate a laboratory requisition form, specifying "G6PD enzyme activity" or "G6PD quantitative assay" for patients with a predisposing racial or ethnic background, as recommended by the HIV Medicine Association of the Infectious Diseases Society of America 1.

Importance of G6PD Testing

G6PD testing is crucial before prescribing certain medications like antimalarials, sulfonamides, and nitrofurantoin, as G6PD deficiency can lead to hemolytic anemia when exposed to these drugs.

Test Procedure

The test requires a blood sample, typically collected via venipuncture, and patients should fast for 8-12 hours before the test for most accurate results.

Handling and Transportation

The blood sample needs to be properly handled as G6PD is temperature-sensitive; it should be transported to the lab promptly, ideally within 2-3 hours of collection.

Test Costs and Availability

The test is commonly ordered through hospital laboratories or commercial reference labs like LabCorp or Quest Diagnostics, and results are typically available within 2-5 business days, with costs approximately ranging from $30-150 depending on location and insurance coverage.

Clinical Guidelines

According to recent guidelines, screening for G6PD deficiency is recommended upon entry into care or before starting therapy with an oxidant drug in patients with a predisposing racial or ethnic background 1, and quantitative G6PD testing is recommended for those with intermediate G6PD deficiency 1.

Key Considerations

It is essential to note that primaquine should not be administered for greater than 5 days in individuals with G6PD deficiency, as it may result in life-threatening hemolysis 1.

From the FDA Drug Label

Due to the risk of hemolytic anemia in patients with G6PD deficiency, G6PD testing has to be performed before using primaquine. The FDA drug label does not provide specific instructions on how to order a Glucose-6-Phosphate Dehydrogenase (G6PD) test, but it states that G6PD testing has to be performed before using primaquine 2 and 2.

From the Research

Ordering a G6PD Test

To order a Glucose-6-Phosphate Dehydrogenase (G6PD) test, the following steps can be considered:

• The test can be ordered by a healthcare provider, typically when a patient is suspected to have G6PD deficiency, especially if they are from an ethnic group with a high prevalence of the disorder 3.
• The test can be performed on a blood sample, and various methods are available, including spectrophotometric testing, fluorescence testing, or formazan-based spot testing 4.
• In some cases, molecular analysis may be required to detect known mutations of the gene encoding G6PD, particularly in females who are heterozygous for the disorder 4.
• New technologies, such as capillary-driven microfluidic chips, are being developed to provide rapid and quantitative G6PD tests, which can be useful in point-of-care settings 5.

Considerations for Ordering a G6PD Test

Before ordering a G6PD test, the following considerations should be taken into account:

• The patient's medical history and symptoms, such as anemia, fatigue, or jaundice, which may indicate G6PD deficiency 4.
• The patient's ethnic background, as certain ethnic groups are more prone to G6PD deficiency 3.
• The potential for the patient to be exposed to oxidative medications or other triggers that can cause hemolysis in individuals with G6PD deficiency 4.
• The availability of G6PD testing in the patient's location, as well as the cost and accessibility of the test 6.

Implications of G6PD Testing

G6PD testing has important implications for patient care, including:

• Identifying individuals with G6PD deficiency who may be at risk of hemolysis due to certain medications or other triggers 4.
• Informing the use of medications, such as rasburicase, primaquine, dapsone, pegloticase, and methylene blue, which should be avoided in individuals with G6PD deficiency until a diagnostic test has been performed 4.
• Ensuring the safe transfusion of blood products, particularly in areas with a high prevalence of G6PD deficiency 7.