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G6PD Test Guide

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What is a G6PD Test?

A Glucose-6-Phosphate Dehydrogenase (G6PD) test is a blood test that measures the levels of G6PD enzyme in your red blood cells. G6PD is an enzyme that helps red blood cells function normally and protects them from harmful substances that may be present in the bloodstream. This test is primarily used to diagnose G6PD deficiency, a genetic condition that can lead to hemolytic anemia when triggered by certain medications, foods, or stress.

Why Are G6PD Tests Performed?

G6PD tests are typically ordered by healthcare providers for several reasons:

  • Unexplained Jaundice or Anemia: To investigate the cause of jaundice (yellowing of the skin and eyes) or anemia, especially if it occurs suddenly.
  • Family History: If there's a known family history of G6PD deficiency, testing may be recommended, especially for newborns.
  • Reaction to Medications: If you've experienced a negative reaction to certain medications known to trigger hemolysis in people with G6PD deficiency.
  • Ethnic Background: G6PD deficiency is more common in people of African, Mediterranean, and Southeast Asian descent, so screening may be recommended for these populations.
  • Pre-medication Screening: Before prescribing certain medications that can trigger hemolysis in G6PD-deficient individuals.

How G6PD Tests Are Performed

The G6PD test is a simple blood test that follows these steps:

  1. A healthcare professional will clean an area on your arm with an antiseptic.
  2. They will insert a small needle into a vein to draw a blood sample.
  3. The blood is collected in a tube and sent to a laboratory for analysis.
  4. The lab measures the level of G6PD enzyme activity in your red blood cells.
  5. Results are typically available within a few days.
Important Note: G6PD tests may show normal results during or immediately after a hemolytic episode because older red blood cells with lower G6PD levels have been destroyed, leaving primarily newer cells with higher enzyme levels. For the most accurate results, the test should be performed when you're not experiencing acute symptoms.

Interpreting G6PD Test Results

G6PD test results are typically reported as units per gram of hemoglobin (Units/g Hb). The normal range for adults is approximately 7-20.5 Units/g Hb, though reference ranges may vary by laboratory.

  • Normal Results: G6PD enzyme levels within the reference range indicate that you likely don't have G6PD deficiency.
  • Low Results: G6PD enzyme levels below the reference range suggest G6PD deficiency. The severity of the deficiency can vary:
    • Class I: Severe deficiency (less than 10% of normal activity) associated with chronic non-spherocytic hemolytic anemia
    • Class II: Severe deficiency (less than 10% of normal activity) without chronic hemolytic anemia
    • Class III: Moderate deficiency (10-60% of normal activity)
    • Class IV: No deficiency (60-150% of normal activity)
    • Class V: Increased enzyme activity (more than 150% of normal activity)

Living with G6PD Deficiency

If you're diagnosed with G6PD deficiency, the main management strategy is to avoid triggers that can cause hemolytic anemia. This includes:

Medications to Avoid

  • Certain antimalarial drugs (e.g., primaquine, chloroquine)
  • Sulfonamide antibiotics
  • Nitrofurantoin
  • Aspirin (in large doses)
  • Certain analgesics and antipyretics
  • Some anti-tuberculosis drugs

Foods to Avoid or Limit

  • Fava beans (broad beans)
  • Certain legumes
  • Foods with artificial blue food coloring
  • Tonic water (contains quinine)

Other Triggers to Avoid

  • Certain infections
  • Severe physical stress
  • Diabetic ketoacidosis
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Preparing for the Test

  • No special preparation or fasting is typically required.
  • Inform your healthcare provider about all medications, supplements, and herbs you're taking.
  • Mention if you've recently had a blood transfusion, as this can affect test results.
  • Discuss any recent illnesses, as they can temporarily alter G6PD levels.
Important: If you're actively experiencing a hemolytic episode, your healthcare provider might recommend waiting until the episode resolves before testing.

Who Should Get Tested?

Consider G6PD testing if you:

  • Have a family history of G6PD deficiency
  • Are of African, Mediterranean, or Southeast Asian descent
  • Have experienced unexplained episodes of jaundice or anemia
  • Have had a reaction to certain medications
  • Are planning to take medications that could trigger hemolysis in G6PD-deficient individuals
Note: Newborn screening for G6PD deficiency is performed in some countries with high prevalence of the condition.

G6PD Deficiency Facts

  • Prevalence: Affects approximately 400 million people worldwide
  • Inheritance: X-linked recessive genetic disorder (more common and usually more severe in males)
  • Geographic Distribution: Most common in Africa, the Mediterranean, the Middle East, and Southeast Asia
  • Evolutionary Advantage: May provide some protection against malaria
  • Severity: Most people with G6PD deficiency live normal lives if they avoid triggers
Did You Know? G6PD deficiency is the most common enzyme deficiency worldwide, affecting an estimated 4-7% of the global population.

When to Seek Medical Help

If you have G6PD deficiency and experience any of the following symptoms, seek medical attention immediately:

  • Sudden paleness or yellowing of the skin or eyes
  • Dark urine
  • Fatigue or dizziness
  • Rapid heart rate
  • Shortness of breath
  • Back or abdominal pain

These could be signs of hemolytic anemia, which requires prompt medical treatment.

Vitamin Deficiency Connection

While G6PD deficiency is not directly related to vitamin deficiencies, maintaining good nutritional status is important for overall red blood cell health. Our vitamin deficiency test can help identify potential nutritional gaps that might impact your overall health.