I read the work by Dr. Schmulson et al.1 with interest, in which they present their experience with the use of the anti-CdtB/anti-vinculin antibodies for confirming the presence of diarrhea-predominant irritable bowel syndrome (IBS-D) in a small group of patients presenting with pain, abdominal bloating, and diarrhea. The authors concluded that their results support the use of this test as a first-line diagnostic tool for confirming the presence of IBS-D (Rome III).1 Obviously, this conclusion exceeds the scope of their study, given that this test has not been adequately validated in the broad clinical spectrum of patients with pain, bloating, and diarrhea, especially those with microscopic colitis (MC).
The correct validation of a diagnostic test demands specific characteristics. First, the test in question should be compared with an accepted or “criterion standard” diagnostic test. The problem is that no “criterion standard” has been defined in relation to IBS-D diagnosis, given that the Rome criteria have insufficient sensitivity and specificity, whereas colonoscopy with biopsies should be carried out in many of the patients with IBS-D.2 In Mexico, 18% of the patients with IBS-D criteria systematically studied with colonoscopy and biopsies present with MC.3 Second, validation must include a wide range of subjects with the clinical symptoms that characterize the disease. Even though in this study patients with tropical sprue, celiac disease, diverticular disease, and MC were included, the number was very small and other entities belonging to the scope of symptoms were not even considered (e.g., intestinal parasitosis, bile acid and carbohydrate malabsorption, exocrine pancreatic insufficiency, or neoplasias). Finally, bias must be prevented by having all the study subjects undergo the test being evaluated, as well as the “criterion standard”, which clearly was not done in this study.
Even though anti-CdtB/anti-vinculin antibody determination has been validated in inflammatory bowel disease, the same has not occurred with MC. In fact, MC is characterized by overlapping with IBS-D, by having a good response to initial treatment with budesonide, high relapse rates, and an elevated response to retreatment.4,5 Thus, the reappearance of pain, bloating, and diarrhea in a patient with MC that responded well to initial treatment should be considered disease relapse, and cannot be taken as evidence of IBS-D with overlapping MC. Relapse occurs in 60-82% of the cases of MC and is the main indication for giving prolonged maintenance treatment.4,5 Studies published up to now that evaluate the use of these biomarkers have included a surprisingly low number of patients with MC, given the prevalence of this disease. The results of the study by Dr. Schmulson et al. reaffirm the need to correctly validate these tests in the wide range of patients with IBS-D criteria, including an adequate number of patients with MC and others with the symptomatic complex of pain, abdominal bloating, and diarrhea that have not yet been taken into account.Conflict of interest
Ramón Carmona-Sánchez is a Member of the Advisory Board of Mayoly-Spindler, a Speaker for Mayoly-Spindler and Allegan, and participates in research protocols funded by Laboratorios Senosian and Asofarma.
Please cite this article as: Carmona-Sánchez R. ¿Están realmente listos los anticuerpos anti-CdtB y anti-vinculina para emplearse en pacientes con diarrea en México? A propósito de la colitis microscópica. Revista de Gastroenterología de México. 2017. http://dx.doi.org/10.1016/j.rgmx.2016.12.003
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