Point of Care Testing for Celiac Disease Lacks Sensitivity

Jennifer Garcia

October 03, 2018

The Simtomax point of care test (POCT) has low sensitivity in screening patients for celiac disease, particularly when used for pediatric patients in whom the probability of celiac disease is high, a study found. The findings were published online September 26 in Clinical Gastroenterology and Hepatology.

"The evidence for a lower-than-expected sensitivity questions the benefits of introducing this POCT into routine clinical practice, e.g. for directing the decision to obtain duodenal biopsies," write lead author Michael Schumann, MD, from the Charité – Universitätsmedizin Berlin and Berlin Institute of Health, Germany, and colleagues.

As part of a prospective study, researchers evaluated 888 adults and 167 children referred for outpatient endoscopy to eight endoscopy centers in Germany between January 2016 and June 2017. Enrolled patients were tested for celiac disease using the Simtomax POCT, which is designed to detect immunoglobulin A and immunoglobulin G antibodies against deamidated gliadin peptides (DGPs). A definitive diagnosis of celiac disease was based on histologic results of duodenal biopsies (evaluated by pathologists blinded to the POCT result) as well as positive antitransglutaminase (tTG) or DPG antibodies.

The authors found that the POCT had a 79% sensitivity (95% confidence interval [CI], 64% - 89%) and a 94% specificity (95% CI, 93% - 96%) in identifying patients with celiac disease. This resulted in positive and negative predictive values of 37% and 99%, respectively. The overall prevalence of celiac disease in the study population was 4.1%.

When adult and pediatric populations were evaluated separately, the sensitivity of the POCT was found to be even lower in the pediatric population, at 72% sensitivity (95% CI, 53% - 86%). Disease prevalence in this population was 19.6%.

Further, the researchers found a high rate of false negative results (nine cases) in the pediatric population. Although the histologic results and the age of the patients were similar to those for patients who received true positive results, the median DGP and tTG titers were significantly lower among patients with false negative results. The study authors propose that low levels of DPG found in the patients with false negative results may have made interpretation of positive results more challenging as a result of the low intensity of the bands used to determine a positive result.

The study authors note that all the false negative results were found at a single center and postulate that the high prevalence of celiac disease at this center (23 of 43 patients) "may account for unmasking a previously unreported sensitivity problem."

Antibody-Based Testing Should Be Interpreted With Caution

Independent commentator Joseph A. Murray, MD, AGAF, spokesperson for the American Gastroenterological Association, told Medscape Medical News: "The lower sensitivity of the POCT in children referred for endoscopy may reflect the higher use of prereferral serology in children or a family history of celiac disease before referral for endoscopy that could expose the Achilles heel of serological testing that is pretest reduction in gluten intake.

"These results also point out that endoscopists should not rely solely on negative serology as a reason to avoid duodenal biopsy that adds minimal if any real risk to that of the procedure," Murray added.

The researchers acknowledge that previous studies have demonstrated sensitivity and specificity similar to more standard tests for celiac disease (eg, tTG serology); however, "[c]ontrary to these data, our study showed lower diagnostic performances for this POCT" and "suggest caution before introducing this POCT into routine clinical practice at this stage."

Support for this study was provided by the Tillotts Pharma AG, the European distributor of Simtomax. The authors and Dr Murray have disclosed no relevant financial relationships.

Clin Gastroenterol Hepatol. Published online September 26, 2018. Abstract

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