G6PD Assay (Glucose-6-Phosphate Dehydrogenase Assay)

Testing Laboratory

Auckland Te Toka Tumai | Auckland Hospital

Department

Haematology

Delphic Registration Code (Alpha Code)

GPD

Test Code (Numeric Code)

1431

Laboratory Handling

Phlebotomy

Collect 1x 4ml EDTA (Lavendar cap) blood sample.

Transport

Transport at ambient temperature (8-24°C). Samples from outside Auckland City Hospital should be transported on ice.

Registration

Registered as GPD

Separating

EDTA - Do not spin.

Laboratory

LabPlus Special Haematology

Test Adds Requirement

Only available as test add by Special Haematology.

Sample Stability

Stable for 24 hours at room temperature. Refrigerated 2°C to 8°C for up to 7 days.

Associated Tests

• G6PD Screen

Turnaround Time

2 days

Specimen Type

• Whole Blood

Specimen Requirements

Tube/Container Type:

Preferred

• EDTA (Lavender Cap)

Preferred Sample Volume (ml)

4

Minimum Sample Volume (ml)

2

No of Samples Required

1

Paediatric Specimen Requirements

Tube/Container Type:

Preferred

• EDTA (Lavender Cap)

Preferred Sample Volume (ml)

1

Minimum Sample Volume (ml)

1

Additional Specimen Information

Whenever possible, it is preferable to analyse specimens from all family members at the same time.
G6PD is stable for 6 days at 4 degrees Celsius and 24 hours at room temperature.
Samples from outside Auckland City Hospital should be transported on ice.

Aliquot Instructions

Sample Type

• Whole Blood

Minimum Volume (ml)

2

Transport to Lab

Ambient (8 - 24 degrees Celsius)
If overnight - Chilled (2 - 8 degrees Celsius)

Test Method

Quantitative ultraviolet spectrophotometry, which measures the rate of NADPH production at 340 nm.

Limitations / Interference

Under normal circumstances G6PD activity contributed by white cells, platelets and serum is relatively small however a borderline normal result may mask carrier status for a heterozygous female. The buffy coat depletion removes virtually all leucocytes, platelets, serum and some reticulocytes.

Reticulocytosis can mask G6PD deficiency. If reticulocytosis is present and G6PD deficiency is suspected, suggest testing when reticulocyte count returns to normal Reticulocytes contain approximately 1.5 x the G6PD level as that of normal mature red cells.

It is not recommended that this assay be performed after or during a severe haemolytic crisis, since the G6PD levels may be falsely elevated.

Inability to reliably detect heterozygous females with intermediate enzyme activity due to random X-chromosome. Female G6PD activity is affected by Lyonisation.

Recent blood transfusions introduce donor red blood cells with normal enzyme levels, masking the patient's underlying G6PD deficiency.

Uncertainty of Measurement

16%

Whenever possible, it is preferable to analyse specimens from all family members at the same time.

Recent blood transfusions introduce donor red blood cells with normal enzyme levels, masking the patient's underlying G6PD deficiency.

Contact Information