Clostridium difficile is an opportunistic pathogen that causes a spect
rum of disease ranging from antibiotic-associated diarrhea to pseudome
mbranous colitis. Although the disease was first described in 1893, th
e etiologic agent was not isolated and identified until 1978. Since cl
inical and pathological features of C. difficile-associated disease ar
e not easily distinguished from those of other gastrointestinal diseas
es, including ulcerative colitis, chronic inflammatory bowel disease,
and Crohn's disease, diagnostic methods have relied on either isolatio
n and identification of the microorganism or direct detection of bacte
rial antigens or toxins in stool specimens. The current review focuses
on the sensitivity, specificity, and practical use of several diagnos
tic tests, including methods for culture of the etiologic agent, cellu
lar cytotoxicity assays, latex agglutination tests, enzyme immunoassay
systems, counterimmunoelectrophoresis, fluorescent-antibody assays, a
nd polymerase chain reactions.