IT may surprise many doctors that coeliac disease now ranks as one of the most common, widespread and underdiagnosed autoimmune illnesses affecting humankind.
Its varied and often insidious clinical behaviour makes it a modern syphilis, the quintessential clinical chameleon, and its ability to hide in plain sight is no better exemplified than by the fact that 1.5% of Australians are affected, but 80% remain undiagnosed.
Emblematic of this problem is the antiquated but widely held notion that it is an uncommon oddity manifesting in malnourished white children. The contrast with my waiting room – which resembles an international meeting of people with coeliac disease of all ages and sizes (from under to overweight), and hailing from Western and Eastern Europe, Southern and Central Asia, the Middle East and North and South Africa – couldn’t be more stark.
Again, this may be a surprise, which leads me to a key message: if you don’t seek, you won’t find. But can testing more smartly or mass screening help us do this better?
Expeditious diagnosis and treatment of unwell patients with coeliac disease improves their health and quality of life and reduces health care expenditure – early detection must be a clinical priority. And while the popularity of the gluten-free diet in this country – much of it driven by people without a medical diagnosis – can be frustrating for us as clinicians, the impact of undiagnosed coeliac disease and increasing medical concern about the risks of unnecessary gluten exclusion reinforces the need for timely assessment.
Understanding the evolving coeliac disease landscape provides perspective. Its prevalence has increased four-fold in the past 60 years. Our understanding of pathogenesis has shifted from a focus on intestinal malabsorption to that of systemic inflammation driven by a genetically-determined, autoimmune-like response to gluten. Far from it being just a childhood illness characterised by failure to thrive and malabsorption, it is now more commonly seen in adults with an average age of 40 years, who have a variety of extra-intestinal manifestations or may even be apparently asymptomatic. “Apparently”, as many asymptomatic patients have occult nutrient deficiencies or osteoporosis, and many report improvement in symptoms and general wellbeing on a gluten-free diet, which indicates that they were neither symptom- nor disease-free to begin with.
While coeliac disease often presents with gastrointestinal upset (think irritable bowel syndrome), iron deficiency or lethargy (think chronic fatigue), the variable presentation may include, often in isolation, headaches, polyarthralgias, infertility, obstetric complications, hepatitis, dermatitis herpetiformis, osteoporosis, autoimmune diseases such as thyroid disease and type 1 diabetes, peripheral neuropathies, depression and neutropenia. Higher rates of sepsis (from splenic hypofunction) and malignancy (especially lymphoma) contribute to a two to four-fold increase in mortality. Crucially, treatment with a strict gluten-free diet reverses the inflammatory mucosal lesion, resolves symptoms and reduces these complications. The development of more autoimmune diseases may even be reduced.
An active case-finding strategy that screens people at increased risk of coeliac disease based on suggestive symptoms or conditions is the currently favoured diagnostic approach. In general practice, this strategy may increase detection rates more than 40-fold, although the lack of control populations in these studies means it is difficult to define its performance. The approach works but is not perfect.
A questionnaire to identify coeliac-specific symptoms and conditions in Swedish children failed to enhance detection of undiagnosed coeliac disease because symptoms were non-specific and asymptomatic disease was common. Others have shown that in the absence of symptoms, a family history of coeliac disease or a history of autoimmune disease are useful markers of disease risk.
What about mass screening? Coeliac disease is common, a good screening test exists, clinical detection is difficult and a treatment is available. Where the case fails is the paucity of data to demonstrate a clear medical and economic benefit to testing and treating asymptomatic disease, where the risk for serious complications is less well described. If the burden of disease in asymptomatic patients can be uncovered, the tide may well turn, but for now mass screening is not the solution. Notably, it will never capture all patients, as coeliac disease may develop at any age, meaning a negative test does not negate a future diagnosis.
So, we are left with an imperfect solution – an active case-finding strategy that detects only a proportion of people with coeliac disease – but hopefully those who will benefit most from treatment. If we are to make this approach work to find this elusive chameleon, it is essential that we understand how coeliac disease can present, maintain a high index of suspicion and pursue aggressive case-finding.
Dr Jason Tye-Din is the head of coeliac research at the Walter and Eliza Hall Institute of Medical Research, and gastroenterology consultant at the Royal Melbourne Hospital. He is chair of Coeliac Australia Medical Advisory Committee.
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