Thalassaemia: More tests needed
Doctors who are testing for thalassaemia, an inherited blood disorder, need to do more precise tests to rule it out.
Parents who are extra cautious and wish to rule out having thalassaemia, an inherited blood disorder, should ask for more precise testing to be done. This is because the testing for thalassaemia varies from doctor to doctor and from country to country, and is often not foolproof.
More thorough testing is required to rule out thalassaemia, which can be a life-threatening disorder.
This was the message by Dr Anselm Lee, a paediatric haematologist-oncologist at Parkway Cancer Centre, at a Continuing Medical Education talk conducted for doctors.
Thalassaemia is a disorder where the body has an abnormal form of haemoglobin, which is the protein molecule in red blood cells that carries oxygen.
There are severe types of thalassaemia. At the extreme ends, there are thalassaemia minor and thalassaemia major. Thalassaemia major is a serious disorder and people with the condition will require monthly blood transfusions to stay alive. Thalassaemia minor is not considered an illness.
According to Dr Lee, the usual method of diagnosing thalassaemia is not sufficiently comprehensive. It begins with a blood count to look at the average volume of red blood cells in a person. If the person has a low mean cell volume (MCV), defined as being less than 80 femtolitres (fL), the person’s blood is then tested to look for different types of haemoglobin.
If those subsequent tests show that the blood is made up of 3.5 per cent or more of haemoglobin A2, the person is diagnosed to have the beta thalassaemia minor trait. Alpha thalassaemia minor, on the other hand, is diagnosed when there is a presence of haemoglobin H (HbH) granules.
However, this process of testing for thalassaemia is not enough to exclude thalassaemia traits. Among other things, not all thalassaemia traits have low MCVs, said Dr Lee. People with the haemoglobin E trait, for instance, may not have low MCVs, he said. In addition, some people with beta thalassaemia may have normal or low numbers for haemoglobin A2 while some with alpha thalassaemia minor do not present with haemoglobin H granules. And people with silent alpha thalassaemia traits may have none of these features.
“A normal MCV report does not exclude thalassaemia minor,” he said. As a result, he advised doctors at the talk: “Never tell patients, ‘You don’t have thalassaemia’, until you have the full truth.”
Between 2009 and 2017, Dr Lee diagnosed four children with severe thalassaemia syndrome in his practice, he said. In two of those cases, the parents had been told by doctors that the pregnancies were not at risk of thalassaemia.
To rule out thalassaemia for his patients, Dr Lee orders three tests. The first is a full blood count with peripheral blood film. This will provide information such as the cell count for each blood type and the concentrations of haemoglobin.
The second test is haemoglobin electrophoresis, including HbH granules identification. This test detects the different types of haemoglobin in the blood and their levels and also aims to look for HbH granules.
The third test is a genetic test for five of the most common missing or inactive genes that cause alpha thalassaemia.
At the talk, Dr Lee also warned doctors to be careful of case reports linking thalassaemia to other conditions such as bipolar affective disorder and arthritis. These reports tend to originate in the West where thalassaemia is relatively uncommon. In places where the trait is common, such as China, Thailand or Singapore, no links to other diseases have been seen, he said.
- Inherited blood disorder in which the body makes an abnormal form of haemoglobin
- 4.4 out of every 10,000 live births around the world affected
- 3-9% of the population affected in Singapore
Serious disorder, needs monthly blood transfusions to stay alive
Not considered an illness, no treatment needed
From minor to life-threatening
Thalassaemia is an inherited blood disorder that comes with different types of severity and forms. At the most severe end, thalassaemia major is a life-threatening condition while at the opposite end, thalassaemia minor is not considered an illness.
Children can inherit the condition from their parents. If only one parent has thalassaemia minor, the child will have a 50 per cent chance of having thalassaemia minor. However, if both parents have the same kind of thalassaemia minor, then there is a 25 per cent chance that the child will develop thalassaemia major.
Thalassaemia is relatively common in Singapore, with studies placing its prevalence at between three and nine per cent of the population. While people with thalassaemia major will require monthly blood transfusions for the rest of their lives, thalassaemia minor is not considered an illness. It does not affect the general health of people with the disorder, nor does it appear to shorten life expectancy.
In fact, most people with thalassaemia minor are unlikely to even notice they have it, said Dr Anselm Lee, a paediatric haematologist-oncologist at Parkway Cancer Centre (PCC).
“Most people live their lives without even knowing they have thalassaemia,” he said. In fact, an Italian study has even suggested that people with thalassaemia minor might be less prone to heart attacks.
Footballer Zinedine Zidane and tennis player Pete Sampras are examples of people with thalassaemia minor. These athletes show that having thalassaemia minor is not an obstacle to living a full life.
Tags: blood disorders, cancer screening, thalassaemia