Celiac disease can be divided into different types. This article describes refractory celiac disease, the diagnostic process and new testing procedures.
In most cases, celiac disease can be treated successfully using a gluten-free diet. However, a very small proportion of sufferers (around 0.5 %) develop refractory celiac disease, meaning that they suffer from celiac-like symptoms despite adhering to a strict gluten-free diet. It is important that refractory celiac disease is diagnosed since it can result in serious secondary diseases (for example, lymphoma diseases, i.e. malignant diseases affecting certain inflammatory cells). Current techniques used to diagnose refractory celiac disease are complex and comprise analyses of the patient’s cells and genetic material (deoxyribonucleic acid, DNA) using tissue extracted via a gastroscopy. These measures aim to identify whether patients who are believed to be suffering from refractory celiac disease are among those also at risk of developing T-cell lymphoma (type II refractory celiac disease), or whether they are suffering from the less serious type I refractory celiac disease. Patients suffering from type II refractory celiac disease must be closely monitored and in some cases require medication. One positive aspect worth mentioning is that the therapy methods developed in recent years, primarily in the Netherlands, to treat the more serious form of refractory celiac disease (type II) represent a clear improvement. Indeed, such improvements in treatment are the reason why it is so important to differentiate between type I and type II as early as possible. However, current diagnostic procedures do not enable a reliable differentiation between these two subtypes in a number of patients. That is why we have decided to focus our research work in Berlin on improving diagnostic techniques in this field using two newly developed testing methods. These will be used on patients suffering from refractory celiac disease type I and type II with the aim of contributing to a reliable diagnosis. Moreover, the results of these tests will be checked against the progression of the disease in the respective patients. We have reason to believe that these new diagnostic tests can reveal information about the future progression of the disease – a valuable contribution that no diagnostic method currently in use is able to deliver.
What kind of tests will be used?
The current diagnostic technique involves subjecting certain cells contained in tissue taken from the small intestine via a gastroscopy to immunostaining and then analyzing these cells under a microscope. In addition, the patient’s DNA is checked for changes in the T-cell receptor using a process known as molecular pathology. The T-cell receptor is a key molecule that sits on the surface of certain inflammatory cells (the T-cells) and plays a central role in the body’s immune response to pathogens. It is only capable of carrying out this role if there are several million different versions of this molecule which, in turn, are capable of identifying a huge variety of bacteria, viruses and parasites. In patients suffering from type II refractory celiac disease, a certain T-cell multiplies so many times that it is identified as a clone by current testing methods. However, in many cases these testing methods are unable to provide a clear result, meaning the doctor cannot be certain whether or not the patient is suffering from the severe form of celiac disease. This is where the new testing methods are designed to make a difference. The first of these methods, the FACS analysis of T-cells from the intestine, removes the inflammatory cells from the tissue and dyes them in a very specific way using antibodies. The antibody binding of tens of thousands of individual cells is then analyzed using a FACS machine (Fluorescent Activated Cell Sorter), which makes it possible to quantify the proportion of “diseased”, or “aberrant”, T-cells. This can be carried out both before and after therapy. According to our theory, the number of aberrant T-cells can be used to determine the patient’s condition during the progression of the disease, i.e. to assess how successful therapy has been. We still have to evaluate to what extent the number of aberrant T-cells at the start can be used to indicate the initial severity of the disease. The second testing method, deep sequencing of T-cell receptors, analyzes the patient’s DNA in a similar way to the molecular pathology technique already used. The difference, however, is that the analyses carried out are significantly more detailed than those used in molecular pathology, as the important part of the T-cell receptor is “sequenced”, i.e. the exact order of the DNA bases is analyzed. Yet, as there is an enormous number of differ-ent T-cell receptor variants, this process must be repeated millions of times – a Herculean task possible today thanks to modern DNA sequencing machines. It is this large number of repetitions that gives “deep” sequencing its name. As with the other new testing method mentioned above, the number of repeating T-cell receptor sequences revealed through this technique can indicate the presence of “T-cell clones” – even, we believe, at an early stage when these clones are still in their infancy.
As may be clear from the descriptions above, these new tests place no additional strain on the patient. Both the existing and the new testing methods require tissue samples taken from the duodenum, the first section of the small intestine. The new testing methods could, however, enable better differentiation between the two different types of refractory celiac disease. Consequently, doctors could know for sure whether or not treatment is required, and could evaluate the success of this treatment by analyzing those cells placed under attack by the treatment. The result is an optimization of the diagnostic process and a more targeted treatment, resulting in a significant benefit for the patient.
DR. MED. MICHAEL SCHUMANN
- Division of Gastroenterology, Infectiology and Rheumatology, Charité, Campus Benjamin Franklin, Berlin.