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Impact of 2-Step Laboratory Testing Procedures for Clostridium difficile Infection on Physicians’ Treatment Decisions

Navas, Maria E. MD*; Tan, Michael J. MD; DiPersio, Joseph R. PhD*

Infectious Diseases in Clinical Practice: March 2013 - Volume 21 - Issue 2 - p 123–125
doi: 10.1097/IPC.0b013e31827cad56
Original Articles

Background Clostridium difficile (CD) is a major cause of hospital-associated diarrhea, and both disease severity and prevalence have increased over the past decade. Our laboratory has used a 2-step algorithm for CD laboratory testing since 2008. In 2011, we replaced the toxin A/B enzyme immunoassay (EIA) confirmatory step-2 part of the procedure with the illumigene molecular assay. This retrospective study evaluated the clinical impact this change had on physicians’ decisions to not start or to stop empiric CD treatment based on negative test results.

Methods Medical records on inpatients from June to December 2010 with glutamate dehydrogenase (GDH) negative test results for Clostridium difficile were first reviewed for physicians’ actions. Additional records from inpatients with GDH-positive/toxin A/B EIA–negative specimens from this same time period and the same number of inpatients with GDH-positive/illumigene-negative specimens from June to December 2011 were also reviewed and the treatment decisions compared.

Results Of 145 patients with GDH-negative test results, 74.5% were never treated for C difficile infection, 20.7% had treatment stopped within 3 days of the test result, and only 4.8% were continued on treatment. Of 60 patients with GDH-positive/toxin A/B EIA–negative test results, 26.7% were never treated, 36.7% had treatment stopped within 3 days, but 36.7% were continued on treatment for more than 3 days. The toxin A/B portion of the 2-step algorithm was changed in early 2011 to the illumigene C difficile molecular assay. Of 60 patients with GDH-positive/illumigene-negative test results, 36.7% were never treated, 48.3% had treatment stopped within 3 days, and only 15% of patients were continued on treatment.

Conclusions Results show that GDH-negative results influence physicians not to treat or to stop empiric treatment for C difficile infection. In addition, more patients were continued on treatment (>3 days) with a toxin A/B EIA–negative result and then with an illumigene-negative result (36.7% vs. 15% respectively, P = 0.007).

A number of laboratories have adopted a two-step approach for C. difficile testing. This retrospective chart review analysis demonstrated that a Glutamate Dehydrogenase EIA NEG test result (step 1) influenced physicians to not treat or to stop empiric CDI treatment within 3 days of test reporting. In addition, use of a molecular method (step 2) to confirm GDH POS specimens resulted in fewer suspected CDI patients continued on empiric treatment for >3 days, compared to a previously used Toxin A/B EIA.

From the *Departments of Pathology and Laboratory Medicine and †Medicine, Summa Health System, Akron, OH.

Correspondence to: Joseph R. DiPersio, PhD, Department of Pathology and Laboratory Medicine, Summa Health System, 525 E Market St, Akron, OH 44304. E-mail:

This work was presented in part at the 112th General Meeting of the American Society for Microbiology, San Francisco, CA, June 16–19, 2012.

Grant support was provided by Merck & Co.

Dr Tan discloses that he has received payment for lectures sponsored by Pfizer, Cubist, Ortho-McNeil, Optimer, Forest, MCE Conferences, and University at Sea.

Dr DiPersio discloses receipt of grant support from Meridian Bioscience, Inc. for past and unrelated present research studies, and a speaker honorarium. He has received research funding from TechLAB for an unrelated study.

Dr Navas has no conflicts of interest to disclose.

© 2013 by Lippincott Williams & Wilkins.