G6PD Deficiency Testing | Glucose-6-Phosphate Dehydrogenase | Cytogenomix® Malaysia
Red Blood Cell Enzyme Disorder

G6PD Deficiency Testing

Comprehensive molecular analysis for Glucose-6-Phosphate Dehydrogenase deficiency. Essential for diagnosis of hemolytic anemia, neonatal jaundice, and pharmacogenetic testing.

400M+ AFFECTED WORLDWIDE
1:3 MALES IN HIGH-RISK POPULATIONS
200+ MUTATIONS
5-7 DAYS TAT

Test Specifications

Technical details for G6PD genetic testing

Test Code G6PD001 (Common Mutations), G6PD002 (Sequencing), G6PD003 (Comprehensive Panel)
Methodology Sanger sequencing, targeted mutation analysis, MLPA for deletions
Gene Analyzed G6PD (Xq28) - 13 exons
Mutations Detected Common variants including G6PD Mediterranean, G6PD A-, G6PD Canton, G6PD Viangchan, G6PD Mahidol, and full sequencing for rare variants
Sample Type 3-5 mL whole blood (EDTA purple top) | Newborn screening cards
Turnaround Time 5-7 working days (targeted) | 10-14 days (sequencing)
Reporting WHO class prediction, enzyme activity correlation, medication guidance
Genetic Counseling Pre- and post-test counseling included

Understanding G6PD Deficiency

Glucose-6-Phosphate Dehydrogenase (G6PD) deficiency is an X-linked genetic disorder that affects red blood cell metabolism. It is the most common human enzyme deficiency worldwide, protecting against malaria but causing hemolytic anemia when exposed to certain triggers.

Key Facts:

  • Inheritance: X-linked recessive - affects primarily males
  • Global Prevalence: Over 400 million people affected
  • Gene: G6PD located on X chromosome (Xq28)
  • Function: Protects red blood cells from oxidative damage

In Malaysia, G6PD deficiency affects approximately 3-5% of males, with higher prevalence in certain ethnic groups. Newborn screening is mandatory.

G6PD X-linked Inheritance

WHO Classification of G6PD Variants

Five classes based on enzyme activity and clinical severity

Class I

<10%

Severe deficiency with chronic hemolytic anemia. Rare variants associated with lifelong anemia independent of oxidative stress.

Class II

<10%

Severe deficiency with intermittent hemolytic anemia. Most common variants including Mediterranean, Canton, Viangchan.

Class III

10-60%

Moderate deficiency with mild intermittent hemolysis. Includes G6PD A- variant common in Africa.

Class IV

60-150%

Normal enzyme activity. Very mild or no clinical symptoms. Includes wild-type variants.

Class V

>150%

Increased enzyme activity. No clinical significance. Extremely rare.

Common G6PD Mutations in Malaysia

Ethnic distribution of clinically significant variants

Mutation cDNA Change Protein Change WHO Class Population
G6PD Viangchan c.871G>A p.Val291Met Class II Thai, Lao, Malaysian Malay
G6PD Mediterranean c.563C>T p.Ser188Phe Class II Indian, Middle Eastern, Mediterranean
G6PD Canton c.1376G>T p.Arg459Leu Class II Chinese, Southeast Asian
G6PD Kaiping c.1388G>A p.Arg463His Class II Chinese, Southeast Asian
G6PD Mahidol c.487G>A p.Gly163Ser Class III Thai, Malaysian Malay
G6PD A- c.202G>A / c.376A>G p.Val68Met / p.Asn126Asp Class III African, African American
G6PD Union c.1360C>T p.Arg454Cys Class II Philippines, Southeast Asian

Common Triggers of Hemolytic Crisis

Medications and substances to avoid in G6PD deficiency

Medications
  • Primaquine
  • Dapsone
  • Sulfonamides
  • Nitrofurantoin
  • Rasburicase
  • Methylene blue
Foods
  • Fava beans (broad beans)
  • Lentils (in some cases)
  • Lupin beans
  • Bitter gourd (karela)
  • Some food colorings
Infections/Chemicals
  • Bacterial/viral infections
  • Naphthalene (mothballs)
  • Henna (in some cases)
  • Vitamin K analogues
  • Methylene blue

Important: Medication guidance should always be based on specific G6PD variant and WHO class. Our genetic reports include personalized medication safety recommendations.

G6PD Deficiency in Malaysia

Prevalence by ethnic group

3-5%
Malay Males
4-6%
Chinese Males
8-12%
Indian Males
1-2%
Females (homozygous)

Female carriers: Approximately 5-10% of females are heterozygous carriers with variable expression due to X-inactivation

X-Linked Recessive Inheritance

Understanding the risk in males and females

Carrier Mother × Normal Father

Xᴳ X
X Y
X X
Xᴳ X
Xᴳ Y
X Y

50% sons affected, 50% daughters carriers

Affected Father × Normal Mother

X Y
Xᴳ Y
Xᴳ X
X Y
Xᴳ X
X Y

100% daughters carriers, 0% sons affected

Males are hemizygous (one X chromosome) - one mutated copy causes deficiency. Females require two mutated copies for deficiency, but may have symptoms due to skewed X-inactivation.

Clinical Manifestations

Spectrum of symptoms in G6PD deficiency

Neonatal Jaundice

  • Occurs in first 24-72 hours
  • More severe in class II variants
  • May require phototherapy
  • Rarely, exchange transfusion

Acute Hemolytic Anemia

  • Triggered by oxidative stress
  • Onset 24-72 hours after exposure
  • Dark urine (hemoglobinuria)
  • Fatigue, pallor, jaundice

Chronic Hemolysis

  • Only in Class I variants
  • Persistent mild anemia
  • Gallstones
  • Splenomegaly

Favism

  • Hemolysis after fava bean ingestion
  • More common in Mediterranean variants
  • Can be severe
  • Avoidance is key

Diagnostic Algorithm

Integrated approach to G6PD testing

Enzyme Activity (Screen)
DNA Confirmation
Variant Identification
WHO Classification

Note: Enzyme testing during acute hemolysis or shortly after transfusion may give false normal results. Molecular testing is preferred in these situations.

Who Should Be Tested?

Indications for G6PD genetic testing

Newborn Screening

All newborns in Malaysia (mandatory) - enzyme testing initially, molecular confirmation for abnormal results

Acute Hemolysis

Individuals presenting with unexplained hemolytic anemia, dark urine, or jaundice after trigger exposure

Pre-treatment Testing

Before starting potentially hemolytic drugs (rasburicase, dapsone, primaquine, high-dose vitamin C)

Family History

Family members of known G6PD deficient individuals, especially for carrier testing in females

Frequently Asked Questions

Common questions about G6PD testing

Can females be affected by G6PD deficiency?

Yes, but less commonly. Females require mutations on both X chromosomes for full deficiency. Heterozygous females may have variable symptoms due to X-inactivation (lyonization), ranging from normal to mildly affected.

Is G6PD deficiency protective against malaria?

Yes, this is why G6PD deficiency is more common in malaria-endemic regions. The enzyme deficiency makes red blood cells less hospitable to the malaria parasite, providing a survival advantage to carriers.

Can G6PD deficiency be cured?

No, it is a lifelong genetic condition. However, with proper avoidance of triggers, most individuals lead normal lives without symptoms. Management focuses on prevention and prompt treatment of hemolytic episodes.

What medications are safe in G6PD deficiency?

Most medications are safe, including paracetamol, ibuprofen, most antibiotics (except sulfonamides), and common pain relievers. Always check with a pharmacist and show them your G6PD card.

Why is molecular testing needed if enzyme test is available?

Enzyme testing can be falsely normal during acute hemolysis (young RBCs have higher enzyme activity) or after transfusion. Molecular testing identifies the specific variant, guides WHO classification, and is essential for carrier detection in females.

Do all G6PD variants cause the same severity?

No, severity varies significantly by variant. Class II variants (e.g., Mediterranean) cause more severe hemolysis than Class III variants (e.g., A-). Our molecular testing identifies the specific variant to guide prognosis and management.

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