Comparison of C. difficile Stool Toxin Concentrations in Adults with Symptomatic Infection and Asymptomatic Carriage using an Ultrasensitive Quantitative Immunoassay.
Clin Infect Dis. 2018 May 17;:
Authors: Pollock NR, Banz A, Chen X, Williams D, Xu H, Cuddemi CA, Cui AX, Perrotta M, Alhassan E, Riou B, Lantz A, Miller MA, Kelly CP
Background: We used an ultrasensitive, quantitative Single Molecule Array (Simoa) immunoassay to test whether concentrations of C. difficile toxins A and/or B in the stool of adult inpatients with CDI were higher than in asymptomatic carriers of toxinogenic C. difficile.
Methods: Patients enrolled as CDI-NAAT had clinically significant diarrhea and positive nucleic acid amplification testing (NAAT), per US guidelines, and received CDI treatment. Potential carriers had recently received antibiotics and did not have diarrhea; positive NAAT confirmed carriage. Baseline stool samples were tested by Simoa for toxin A and B.
Results: Stool toxin concentrations in both CDI-NAAT (n = 122) and Carrier-NAAT (n =44) cohorts spanned five logs (0 pg/mL to >100,000 pg/mL). 79/122 (65%) CDI-NAAT and 34/44 (77%) Carrier-NAAT had toxin A+B concentration >20 pg/mL (clinical cutoff). Median toxin A, toxin B, toxin A+B and NAAT Ct values in CDI-NAAT and Carrier-NAAT cohorts were similar (toxin A, 50.6 vs 60.0 pg/mL, p=0.959; toxin B, 89.5 vs 42.3 pg/mL, p=0.788; toxin A+B, 197.2 vs 137.3 pg/mL, p=0.766; Ct, 28.1 vs 28.6, p=0.354). However, when CDI/Carrier cohorts were limited to those with detectable toxin, respective medians were significantly different (A, 874.0 vs 129.7, p=0.021; B, 1317.0 vs 81.7, p=0.003, A+B, 4180.7 vs 349.6, p=0.004; Ct, 25.8 vs 27.7, p=0.015).
Conclusions: Toxin concentration did not differentiate an individual with CDI from one with asymptomatic carriage. Median stool toxin concentrations in groups with CDI versus carriage differed, but only when groups were defined by detectable stool toxin (versus positive NAAT).
PMID: 29788296 [PubMed - as supplied by publisher]