Clostridium difficile: Which Test to Order and How Often?

October 21, 2013
Roula Baroudi, MD

Which test should you order if you suspect Clostridium difficile infection-and how often do you check the stool for the C difficile toxin? Here: the answer-and explanation.

Advances in environmental sanitation, immunizations, antimicrobial therapy, and medical research have greatly reduced the impact of infectious diseases (IDs) on our communities. Nonetheless, infections and the cost of treating them remain a burden to the health care system.

In primary care practice, we may spend more time making referrals for suspected ID than actually treating infected patients. Here, as a brush up, is the tenth and final in our series of 10 practical ID pearls.

Pearl #10. Which test should you order if you suspect a case of Clostridium difficile infection and how often do you check the stool for the C difficile toxin?

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Then, click here for answer and explanation

Answer: At present, the specific test performed depends on the individual institution.

The Society for Healthcare Epidemiology of America (SHEA) and Infectious Diseases Society of America (IDSA) recommend a two-step testing process. Glutamate dehydrogenase (GDH) has 70% to 80% sensitivity; thus, if the GDH test is negative, no further action is required. If the GDH testing is positive, you need to proceed with a bacterial culture because of the lack of the specificity (90%) of the GDH test. It is worth mentioning the SHEA/IDSA guidelines came out in 2010, while the polymerase chain reaction (PCR) testing for C difficile came to light in 2011 based on findings of many published studies. It is anticipated that IDSA may adopt PCR as the test of choice when guidelines are updated.

The recommended frequency of C difficile testing was recently limited.

According to the most recent literature supporting the use of PCR for C difficile testing, clinicians do not need to repeat the test any sooner than 1 week.1,2

TESTSensitivity (%)Specificity (%)Turn-Around Time
Toxin A/B enzyme immunoassay (EIA)40-8090Hours
Glutamate dehydrogenase (GDH)70-80<90Hours
Combined GDH & toxin A/B EIA56-90>90Hours
DNA amplification (molecular)>90>97Hours
Cell culture cytotoxin assay70-80>902 days to > 3 days
Toxigenic culture>9095-972 days to > 3 days

1. Tenover F, Novak-Weekley S, Woods C, et al. Impact of strain type on detection of toxigenic Clostridium difficile: comparison of molecular diagnostic and enzyme immunoassay approaches. J Clin Microbiol. 2010;48:3719-3724.
2. Quinn CD, Sefers SE, Babiker W, et al. C. Diff Quick Chek complete enzyme immunoassay provides a reliable first-line method for detection of Clostridium difficile in stool specimens. J Clin Microbiol. 2010;48:603-605.
3. Peterson L, Robicsek A. Does my patient have Clostridium difficile infection? Ann Intern Med. 2009;151:176-179.

Click below for all previous ID Pearls:

Practical ID Pearl #1

Pracitcal ID Pearl #2

Pracitcal ID Pearl #3

Pracitcal ID Pearl #4

Pracitcal ID Pearl #5

Pracitcal ID Pearl #6

Pracitcal ID Pearl #7

Pracitcal ID Pearl #8

Pracitcal ID Pearl #9