Saturday, 8 March 2014

Should there be population screening for coeliac disease ?

Should there be population screening for coeliac disease ?

This Post follows two previous posts on the subject of Coeliac Disease

Anaemia is one of the classical features of coeliac disease and so it follows logically that if someone is found to be anaemic, that person might have coeliac disease. It is suggested that 5% of people with iron deficiency anaemia have coeliac disease.

Anaemia, low haemoglobin concentration in the blood, has many causes. In most cases there is an impairment of the production of red blood cells. This can be the result of specific disease of the bone marrow, where red blood cels are produced. Anaemia can also be due to the absence of an essential factor in the synthesis of haemoglobin, the oxygen-carrying complex that is within the red cells. The three essential factors are iron, folic acid and vitamin B12. Shortage of iron is usually due to blood loss, occasionally dietary shortage of iron, and rarely the malabsorption of iron from food through the intestinal wall into the blood-stream. This is what happens in coeliac disease.

Causes of iron deficiency anaemia:
                   Menstruation        20%
                       Cancer colon       5–10%
            Cancer stomach     5%
             Coeliac disease      5%
            Poor diet                 5%

Not all people diagnosed with coeliac disease develop anaemia. The coeliac disease blood test is so commonly positive with the condition being unrecognised, and so it does not follow that coeliac disease when diagnosed will necessarily be the cause of anaemia.  

It is simple to treat deficiency of iron or folic acid with a course of tablets. It then follows that additional life-long gluten free diet might not give an advantage. 

A 86 year old man was found to have anaemia. His family doctor referred him for a gastroscopy, wondering quite rightly whether or not he had a bleeding lesion in the stomach. He did not, but the endoscopist rather enthusiastically took a biopsy from the duodenum, knowing that coeliac disease might cause anaemia. The biopsy showed partial villous atrophy, the typical appearance of coeliac disease, and the man was sent to my outpatient clinic for further evaluation. His anaemia had been treated and he felt as well as he could expect for his age. Should he be advised to take a gluten free diet? The answer was clearly “No”. It is important to treat a person and not just a biopsy specimen. There would be nothing to gain from him taking a gluten free diet and in this particular case there would be a great deal to lose. He lived alone and he could not cook – he had depended on his wife for sustenance until her death a few years earlier. His present diet seemed to bread either as toast or sandwiches. No wonder he had developed iron deficiency anaemia. A gluten free diet would have brought about his death from starvation.

Is there a place for screening

I have noticed that paediatricians are keen on case-finding. It is known that although coeliac disease does not follow a Mendelian inheritance pattern it is more common in a family member. After diagnosing coeliac disease in a child a paediatrician might tell the family doctor to arrange screening blood test for other family members. I remember well the father of a child newly diagnosed with coeliac disease being sent to me with a positive coeliac blood test. He was a fit and healthy young man without anaemia and without symptoms. Was there are point in trying to coerce him into a life-long gluten free diet? 

This was a long time ago but it made me stop and think about case-finding among the asymptomatic. It is very simple, just a blood test. Much more simple that mammography or cervical cytology. It leads to “diagnosis” but to no more than that. There is certainly no national enthusiasm for screening for coeliac disease, but very enthusiastic individuals might emerge – they usually do and cannot be kept down.

Wheat intolerance 

Many people with intestinal disorders are classified as irritable bowel syndrome. They often find that bread makes them worse and avoidance of bread an other wheat products helps. Testing for coeliac disease will occasionally be positive but it will be negative in the majority. This might come as a disappointment as the diagnosis of coeliac disease is something very positive. Furthermore with this diagnosis will come the entitlement to certain gluten free food products on prescription.

What is happening in people with wheat intolerance but negative coeliac testing is that the intestinal tract cannot handle wheat (not just gluten), probably because of an imbalance of intestinal bacteria. They will take a gluten free diet, best called a wheat free diet and they should not be labelled as having coeliac disease.

It is estimated that in the past only about ten per cent of people with coeliac disease were diagnosed. The simplicity of diagnosis since the introduction of the coeliac disease blood test makes it possible for many more to be diagnosed. These could be people with minimal “illness” such as mild anaemia, usually without symptoms but noted on routine testing. Population screening for coeliac disease would be based on people with no symptoms and no suspicion of illness. Positive testing would lead to the imposition of an unwelcome diet with no significant advantage. Although there will inevitably be enthusiasts for coeliac disease screening, the objective view is that although it would be very easy, it would be of no value.