Coeliac Disease (CD) is a chronic disease which affects at least 1% of the population, with evidence suggesting that its prevalence is increasing. Currently, the only treatment consists of permanent exclusion of gluten from the diet. Associate Professor Mirette Saad, Consultant Chemical Pathologist and the National Director of Molecular Genetics at Australian Clinical Labs explains that a series of steps need to be carefully followed to achieve an accurate diagnosis and avoid patients being misdiagnosed.

“CD is a chronic gluten intolerance that occurs in genetically predisposed individuals. It is one of the most common auto-immune diseases, causing the immune system to react abnormally to gluten, resulting in small bowel damage. Clinical manifestations of CD vary greatly according to age group but can include unexplained bloating or abdominal distress, chronic diarrhoea or constipation, abdominal distention, bloating or pain, and vomiting. Extraintestinal manifestations can include developmental delay, short stature, iron deficiency anaemia, vitamin deficiency, sudden or unexpected weight loss, autoimmune disease, osteoporosis, arthritis, chronic fatigue, weakness, and hair loss. Some CD patients may also be asymptomatic.

“Untreated CD can lead to several long-term complications for patients, such as malnutrition, autoimmune liver disease, peripheral nerve damage, and intestinal malignancies, all of which can severely affect quality of life. It is important to provide an accurate diagnosis to avoid patients being misdiagnosed and unnecessarily implementing restrictive life-long changes to their diet. To do this, a series of steps must be carefully followed,” said A/Prof Saad.

Pathologists play an important role in the recognition and diagnosis of CD. Given the broad clinical presentation of CD, pathology is crucial to identify at-risk patients. In addition to the diagnostic intestinal biopsies, an array of serological and human leukocyte antigen (HLA) genotyping markers along with gluten challenge workup is needed to accurately diagnose and monitor CD.

Provided a patient is eating a gluten-containing diet, diagnosis usually starts with CD serology. Patients who have positive serological testing will have their diagnosis confirmed with the gold standard duodenal mucosal biopsy. Because CD can be present despite negative CD serology (small percentage of patients), correlation of histology and serology is crucial.

“It is important to be tested for CD before introducing a gluten-free diet as eliminating gluten may make the results of blood tests appear normal. The strong association between CD and specific HLA genes makes HLA genotyping a useful tool in specific situations. While HLA genotyping does not have an absolute diagnostic value it can be used in the diagnostic process and is helpful in excluding or predicting CD relative risk.

“HLA genotyping is routinely requested by clinicians to provide additional support in dubious CD cases, i.e., uncertain or discrepant serology and/or biopsy, and in at-risk categories. HLA genetic test is useful in screening first degree relatives due to the higher prevalence of CD among relatives of coeliac patients and is an efficient tool to discriminate individuals who regularly require clinical and serological controls,” said A/Prof Saad.

Following diagnosis, patients with CD should be reviewed regularly, with attention to symptoms, adherence to the gluten free diet, growth (in children), monitoring for complications and provision of preventive health initiatives.