G6Pd Test: Purpose, Test Details & Results

Purpose of G6Pd Test

Understanding your risk before taking certain medications or facing specific health challenges is crucial. The Glucose-6-Phosphate Dehydrogenase (G6PD) test is a key diagnostic tool that helps identify people with G6PD deficiency—a genetic condition affecting red blood cell health. This test protects patients from potentially severe reactions, especially when specific drugs or illnesses could trigger dangerous hemolysis (breakdown of red blood cells). Early detection of G6PD deficiency can prevent life-threatening complications, particularly in newborns and individuals living in malaria-endemic regions.

Table 1: Main Purposes of G6PD Testing

Why Test for G6PD Deficiency?

G6PD deficiency is the most common enzymatic disorder of red blood cells worldwide. While most people with the deficiency never experience symptoms, exposure to certain triggers can cause acute and sometimes life-threatening hemolysis. These triggers include:

• Specific medications: Antimalarial drugs such as primaquine and tafenoquine, as well as sulfa drugs, nitrofurantoin, and some antibiotics 1 2 4 5 7 8.
• Infections: Some bacterial or viral infections can precipitate hemolysis in G6PD-deficient individuals 1.
• Foods: Fava beans are a classic dietary trigger for hemolysis in these patients 1.

Protecting Vulnerable Populations

Newborns

G6PD deficiency is a leading cause of severe neonatal jaundice and kernicterus, particularly in high-prevalence areas. Early identification through newborn screening enables prompt management, reducing the risk of permanent neurological damage 1 3 5.

Malaria-Endemic Regions

In places where malaria is common, G6PD testing is vital before prescribing radical cure therapies like primaquine and tafenoquine. Without this screening, treatment can inadvertently cause life-threatening hemolysis 1 4 5 7 8.

Personalized Medicine and Public Health

Routine screening empowers safer prescribing practices and supports public health strategies, such as malaria elimination programs. It also helps guide family planning and genetic counseling in high-risk populations 1 3.

G6Pd Test Details

When it comes to G6PD testing, advances in diagnostic technology have expanded access to both laboratory-based and point-of-care options. Understanding test types, sample collection, accuracy, and practical considerations can help patients and clinicians choose the right test for their needs.

Table 2: Overview of G6PD Test Methods

Types of G6PD Tests

Laboratory-Based Spectrophotometric Assays

• Gold standard method: Measures G6PD enzyme activity quantitatively.
• Requires a laboratory setting, equipment, and trained personnel.
• Provides precise assessment, reported as units per gram of hemoglobin (U/g Hb).
• Results can take several hours to days 1 4 5 6 7.

Quantitative Point-of-Care (POC) Tests

• Portable, user-friendly devices (e.g., STANDARD™ G6PD, CareStart™ Biosensor).
• Can use finger-prick (capillary) or venous blood.
• Deliver quantitative or semi-quantitative results within minutes at the bedside or clinic.
• High sensitivity and specificity for detecting deficiency (<30% normal activity) and intermediates 1 4 6 7 8.

Qualitative Rapid Tests

• Chromatographic or colorimetric strip-based tests.
• Detect presence or absence of G6PD activity (deficient/normal).
• Particularly useful in resource-limited settings for quick screening.
• Slightly less precise for intermediate cases and female carriers 2 3 6 8.

Paper-Based Analytical Devices

• Innovative, ultra-low-cost solution.
• Color change indicates enzyme activity; can be analyzed visually or with simple imaging tools.
• Highly correlated with standard lab methods; ideal for remote and low-resource settings 3.

Sample Collection and Handling

Blood Sample Sources

• Both capillary (finger-prick) and venous blood are acceptable for most G6PD tests.
• Studies show little difference in accuracy between sample types 1 4 6 7.

Sample Storage

• Enzyme activity can decrease if samples are kept at room temperature for extended periods.
• Optimal to store samples at 4°C and perform testing within 4 days to preserve accuracy 6 7.

Test Accuracy and Performance

• Modern quantitative POC tests and advanced rapid tests show high sensitivity (up to 100%) and specificity (>95%) for detecting severe deficiency 1 2 4 6 8.
• Qualitative tests may be less effective in identifying female carriers or intermediate deficiency due to mosaicism from X-chromosome inactivation 1 2 8.
• Paper-based and low-cost tests are promising for large-scale screening but require further validation for intermediate cases 3.
• Laboratory-specific reference ranges and adjusted male medians are used to interpret results accurately 5 7.

Practical Considerations

• Training: Minimal training is needed for rapid and POC tests; field studies suggest that community health workers can be successfully trained to administer these tests 8.
• Cost and Accessibility: Paper-based and rapid POC tests are affordable and scalable, crucial for high-prevalence or resource-limited settings 3 6 8.
• Environment: Most modern POC tests perform reliably across a range of temperatures and field conditions 1 4 6.

G6Pd Test Results & Follow-Up

Interpreting G6PD test results enables patients and healthcare professionals to make informed, safe decisions about medications and risk management. Understanding what results mean and the next steps is vital for optimal care.

Table 3: G6PD Test Result Interpretation and Recommended Actions

Understanding Your G6PD Test Results

Deficient (<30% Activity)

• What it means: High risk for hemolysis if exposed to certain medications or infections.
• Follow-up: Strict avoidance of contraindicated drugs (e.g., primaquine, tafenoquine, sulfa drugs). Warn healthcare providers of your status. Consider genetic counseling for family planning 1 4 5 6 7 8.

Intermediate (30–70% Activity)

• What it means: Moderate risk—often seen in heterozygous females due to X-chromosome inactivation (“mosaicism”).
• Follow-up: Caution with potentially hemolytic drugs. Additional testing may be required to clarify risk, especially if female. Health professionals may recommend close monitoring during treatment 1 4 5 6 7.

Normal (>70% Activity)

• What it means: Low risk for hemolysis from standard triggers.
• Follow-up: Standard drug protocols may be used; no special precautions necessary 1 4 5 6 7.

Special Considerations for Females

• Females can carry one normal and one deficient gene, leading to intermediate enzyme activity. Quantitative tests are better than qualitative ones at identifying these cases, which is important since they may still be at risk 1 4 5 6.

Next Steps After Testing

Patient Education

• Patients with G6PD deficiency should be informed about their condition and given a list of drugs and foods to avoid.
• Education should include signs of hemolysis: dark urine, yellowing of the skin/eyes, fatigue, and rapid heart rate.

Ongoing Monitoring

• Re-testing may be needed in newborns with high bilirubin or if results are borderline.
• In malaria-endemic areas, repeat testing may be recommended before each radical cure treatment if status is unknown 1 4 5 7 8.

Implications for Treatment

• G6PD status guides safe prescription of antimalarial drugs and other medications.
• In some regions, G6PD testing is becoming standard before treating malaria to prevent avoidable harm 1 4 5 7 8.

Conclusion

The G6PD test is a critical tool for safeguarding patient health in various clinical and public health scenarios. Reliable, accessible testing enables patients and providers to avoid life-threatening complications, especially in vulnerable populations and high-risk settings.

Key Points:

• Purpose: G6PD testing prevents hemolysis from medications, infections, and certain foods, protecting newborns and people in malaria-endemic regions 1 2 4 5 7 8.
• Test Details: Multiple test types are available, including laboratory-based, point-of-care, rapid, and paper-based devices, all showing high accuracy and adaptability to different environments 1 2 3 4 6 8.
• Results: Test interpretation is based on enzyme activity levels, guiding safe medication use and risk management. Special caution is needed for intermediate results, especially in females 1 4 5 6 7 8.
• Follow-Up: Education and ongoing vigilance are essential for those diagnosed with deficiency, ensuring safe healthcare decisions and preventing complications.

By expanding access to accurate and rapid G6PD testing, healthcare systems can better protect patients and advance global health priorities, especially in regions most at risk.