Quantitative fecal lactoferrin was measured in 112 patients tested for toxigenic Clostridium difficile using glutamate dehydrogenase (GDH) and toxin immunoassays combined with tcdB PCR. Lactoferrin levels were higher in the GDH-positive/toxin-positive group (79 g/ml) than in the GDH-positive/toxin-negative/PCR-positive (21 g/ml) and the GDH-negative groups (13 g/ ml). Differences in fecal lactoferrin levels suggest variable presence or severity of C. difficile infection among toxin-positive and toxin-negative patients. Diagnostic testing for Clostridium difficile infection (CDI) may be accomplished through (i) organism detection by anaerobic culture or glutamate dehydrogenase (GDH) immunoassay with subsequent confirmation of toxigenicity, (ii) toxin detection by cell cytotoxicity neutralization assay (CCNA) or enzyme immunoassay (EIA), and (iii) nucleic acid amplification tests (NAAT) for tcdA, tcdB, and/or other C. difficile genes. Given that the rate of positivity of NAAT assays and GDH immunoassays approaches that of toxigenic culture (1, 2), while those of CCNA and EIA are significantly lower (3), universal testing by NAAT or by multistep GDH screening algorithms is endorsed by IDSA/ SHEA consensus (4). Because toxin production is necessary for organism pathogenesis, however, debate persists as to whether direct toxin measurements may offer a theoretical advantage with respect to clinical specificity (5, 6). If toxin positivity were a better indicator of CDI than NAAT positivity, it would follow that levels of fecal lactoferrin (a measure of colonic inflammation) should be higher in toxin-positive patients than in NAAT-positive/toxinnegative patients. The aim of this study, therefore, was to assess fecal lactoferrin values among toxin-positive, NAAT-positive/ toxin-negative, and NAAT-negative/toxin-negative patients.Based upon results from a single academic medical center of a routine, two-step C. difficile diagnostic algorithm (7), which incorporates GDH and toxin A/B lateral flow EIA (C. Diff Quick Check Complete; TechLab, Blacksburg, VA) with tcdB PCR (Gene Xpert; Cepheid, Sunnyvale, CA), 112 previously frozen, unique patient stool samples were selected for study inclusion. Fecal lactoferrin levels were determined for all samples using quantitative enzyme-linked immunosorbent assay (ELISA) (IBD Scan; TechLab, Blacksburg, VA) as per the manufacturer's instruction with a modification (to improve assay precision) that initial specimen aliquots were weighed to the nearest 0.001 g and diluted 1:10 (wt/vol) in kit diluent. A final dilution of 1:500 was used for all samples. Patient electronic medical records were queried to determine history of immunosuppression, inflammatory bowel disease (IBD) and/or prior bowel surgery, results of other stool studies, and peripheral white blood cell (WBC) count within 48 h of C. difficile testing. Data were analyzed using a statistical software program (Minitab 16), and Mann-Whitney U test and Fisher's exact test were used to study group differences in lactoferrin levels.Coe...
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