Table 2.

Tests for Clostridium difficile infection ⁷

Test	Details
GDH EIA	GDH is a protein that is present in all isolates of C difficile. This test is sensitive, quick and relatively cheap, but lacks high specificity for toxigenic forms of C difficile. It is therefore often used as an initial screening test
Toxin A and B EIA	This test has high specificity but variable degrees of sensitivity
Toxin A and B PCR	This PCR test is specific for genes encoding toxins that are produced by C difficile, but a positive result does not help to distinguish active toxin production from asymptomatic carriage of toxigenic C difficile
Cell culture cytotoxicity assay	This is still widely recognised as the reference standard test, although it is rarely performed in most clinical laboratories

Given the variability of the sensitivity and specificity of these tests, a two-stage testing algorithm is widely applied. In the UK, toxin A/B enzyme immunoassay (EIA) testing is often used after an initial glutamate dehydrogenase (GDH) or polymerase chain reaction (PCR) screen⁷