Press briefing moderator Dr. Michael E. Cox of the Mercy Medical Center in Baltimore, said, "The $64,000 question is, when would this possibly be ready for prime time?"
"We are validating this antibody every day," Dr. Pimentel replied, although as yet, no companies are collaborating in developing the assay. "When it will be ready for prime time, I’m not sure."
In the study, the investigators assayed serum samples from 162 prospectively identified patients who met Rome III criteria for IBS, 30 patients with active IBD who were not receiving biologic agents, and 26 consecutive healthy individuals.
Across groups, about 70% of patients were female, with no significant differences in the sex and age distributions.
Results showed that the anti-vinculin antibody optical density (OD) reading was higher in patients with IBS than in patients with IBD (P less than .01) and healthy individuals (P less than .01), reported Dr. Pimentel.
Meanwhile, the anti-CdtB antibody OD reading was higher in the patients with IBD than in the patients with IBS (P = .02).
For distinguishing IBS from IBD, an anti-vinculin antibody OD reading exceeding 0.8 had a sensitivity of 43%, a specificity of 73%, and a positive predictive value of 90%.
There is a good rationale for simultaneously looking at anti-CdtB and anti-vinculin, according to Dr. Pimentel: In the model of postinfectious IBS, anti-vinculin antibodies persist over time, whereas anti-CdtB antibodies decline.
And indeed, in the study, the difference between the two OD readings (anti-vinculin minus anti-CdtB) was higher in the patients with IBS than in both the patients with IBD (P less than .0001) and the healthy individuals (P less than .001).
For distinguishing IBS from IBD, a difference exceeding 0.2 had a sensitivity of 41%, a specificity of 88%, and a positive predictive value of 94%.
A confounding issue is that about 10% of patients with IBD also have IBS, Dr. Pimentel noted. But a model taking this into account showed high positive predictive values for an anti-vinculin antibody OD reading exceeding 0.8 (92%) and for a difference between the OD readings of anti-vinculin and anti-CdtB exceeding 0.2 (97%).
Dr. Pimentel disclosed no relevant conflicts of interest.