A Study Comparing the Premier Toxins A & B and C. difficile TOX A/B II Assays for Diagnosis of Clostridium difficile Infection

Kaiser Permanente Regional Reference Laboratory, North Hollywood, California, 11668 Sherman Way, North Hollywood, California 91605

^* To whom correspondence should be addressed. Email: Susan M. Novak{at}kp.org.

	Abstract

Clostridium difficile causes nosocomial diarrhea and is responsible for complications including pseudomembranous colitis, megacolon, or perforation. Using 442 stool specimens, we compared sensitivity and specificity of the Premier Toxins A & B (Meridian Bioscience, Inc.), and C. difficile TOX A/B II (TechLab, Inc., Blacksburg, VA) immunoassays in the Kaiser Permanente Regional Reference Laboratories, Virology Department. The Premier Toxins A & B assay demonstrated higher sensitivity (97.44%) and positive predictive value (79.17%) than the C. difficile TOX A/B II assay (87.18% and 75.56%) while assay specificities and negative predictive values were similar.

We also performed experiments using serially diluted purified toxin A and B antigens to understand the basis for assay differences. Both assays' toxin A antibodies detected toxin A at comparable levels. Preliminary results indicated the Premier Toxins A & B toxin B antibody could detect toxin B at a 125 pg/100 µl concentration, while the C. difficile TOX A/B II toxin B antibody could not detect toxin B below the 250 pg/100 µl concentration. Therefore, the Premier Toxins A & B assay provides greater sensitivity than the C. difficile TOX A/B II assay, perhaps due to a superior detection ability of its toxin B antibody.