Table 1.
Diagnostic tests for toxigenic C. difficilea
| Testing Method | Target(s) | Notes |
|---|---|---|
| Gold Standard Tests | ||
| Toxigenic Culture | Toxigenic C. difficile | • Reference standard |
| • Difficult to perform | ||
| • Time consuming (24–48 hours) | ||
| Cell Cytotoxicity Assay | Toxins A or Bb | • Reference standard |
| • Highly sensitive for toxin compared to EIA | ||
| • Difficult to perform | ||
| • Time consuming (24–48 hours) | ||
| Rapid Diagnostic Tests | ||
| EIA | GDH | • GDH alone insufficient for diagnosis (must be paired with a test for toxin) |
| • Rapid | ||
| • Variable sensitivity and specificity | ||
| EIA | Toxins A or Bb | • Rapid |
| • Variable sensitivity and specificity | ||
| NAAT | • Rapid but more expensive than EIA | |
| • Highly sensitive and specific for presence of toxigenic C. difficile | ||
| • May increase detection of colonization and not true CDI | ||
| RT-PCR | tcdB or tcdC genes | • tcdA- / tcdB+ strains can cause disease |
| LAMP | tcdA or tcdB genes | • tcdA+ / tcdB- not well-described in human disease |
| • Caution required in interpreting negative results based on tcdA testing alone by LAMP |
Abbreviations: CDI, Clostridium difficile infection; EIA, enzyme immunoassay; GDH, glutamate dehydrogenase; LAMP, loop-mediated isothermal amplification; NAAT, nucleic acid amplification testing; RT-PCR, real-time polymerase chain reaction.
a
Refer to the text or Table 2 / Appendix C for sensitivity / specificity of the diagnostic tests
b
C. difficile can produce toxin A and/or toxin B. Although both play a role in clinical disease, it is not known if strains producing only toxin A are associated with symptomatic infection in humans.