At a glance
Also known as
Why get tested?
To determine whether you have an inherited G6PD deficiency, necessary to keep red blood cells healthy.
When to get tested?
If a child experienced persistent jaundice as a newborn that was not due to another identified cause; when you have had one or more intermittent bouts of haemolytic anaemia that appear to be due to an caused by some medicines, foods, or infections.
A blood sample drawn from a vein in your arm
What is being tested?
This test measures the amount of glucose-6-phosphate dehydrogenase (G6PD) in the red blood cells (RBCs). G6PD is an that protects red blood cells from the effects of oxidation. If there is insufficient G6PD, the RBCs become more vulnerable to . If these RBCs are exposed to an oxidative agent (for a list, click here), it changes their cellular structure, precipitating haemoglobin inside the cells (), causing them to break apart ().
G6PD deficiency (most severe form is called Favism) is the most common enzyme deficiency in the world, affecting about 400 million people according to the Nemours Foundation. It may be seen in up to 20% of the population in Africa, 4-30% in the Mediterranean and is found in Southeast Asia. or changes in the G6PD may lead to the production of a G6PD enzyme that has diminished functionality or stability. This is expressed as decreased enzyme activity levels.
So far, more than 440 G6PD gene variations have been identified and can cause enzyme activity deficiencies of varying severity depending on the mutation and on the individual person. The G6PD gene is located on the X . Since males have one X and one Y chromosomes, a single X chromosome carrying the faulty G6PD gene with no additional healthy X chromosome will result in G6PD deficiency. Males inherit the condition from their mother.
Females have two X chromosomes, thus two copies of the G6PD gene could possibly be inherited. females (those with only one altered gene) can produce enough normal G6PD that they usually do not experience any . However, the presence of the abnormal form may be identified if the deficiency is detected in their male children. Rarely, a female may be , having two altered G6PD genes (the same or different mutations), and thus will experience G6PD deficiency.
In newborns, G6PD deficiency may cause persistent jaundice. Left untreated, this jaundice can lead to brain damage and mental retardation.
Most people with G6PD deficiency can lead fairly normal lives, but they must be cautious to avoid certain medications (aspirin, sulphonamides, quinine, Dapsone), foods (such as fava beans), and chemical substances (such as naphthalene, found in moth balls), which can cause oxidative stress resulting in a haemolytic crisis. A comprehensive list is found on the G6PD Deficiency Favism Association website. Infections, either or , can also cause oxidative stress and lead to bouts of haemolytic anaemia. With haemolytic anaemia, RBCs are destroyed at an accelerated rate and the patient becomes pale and fatigued (anaemic) as their capacity for providing oxygen to their body decreases. In some cases, jaundice can also be present during episodes of haemolysis. Most of these episodes are self-limiting, but if a large number of RBCs are destroyed and the body cannot replace them fast enough, then the affected patient may require a blood transfusion or even develop kidney problems. A small percentage of those affected with G6PD may experience anaemia.
How is the sample collected for testing?
A blood sample is obtained by inserting a needle into a vein in the arm.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.
Why is the detection of G6PD deficiency important?
The detection allows patients to work with their doctor and to educate themselves about a condition that will affect them to some degree for the rest of their lives. It also allows patients to talk to the doctor about how this trait is inherited and the potential impact it may have on their children. By knowing about the deficiency and avoiding potential triggering substances and situations, most of those who have G6PD deficiencies can lead relatively normal lives.
Is it important to determine which mutation I have?
Not for you personally, but it may aid in detecting the mutation in other family members. Genetic testing usually only tests for the most common mutations. If you have one of the common mutations, then testing other family members for that mutation is useful in establishing familial patterns.
Do I need to tell a new doctor that I have a G6PD deficiency if I do not have any symptoms?
Yes, this is an important part of your medical history and will affect future procedures and treatment options. Your doctor needs to know if you have a G6PD deficiency or if you know that you are an . As noted, a variety of drugs can exacerbate the haemolytic episode, requiring immediate attention including a blood transfusion.