Who are susceptible to pseudomembranous colitis among patients with presumed antibiotic-associated diarrhea?

Purpose: Pseudomembranous colitis is a severe form of antibiotic-associated diarrhea. However, there have been no reports about the factors that make patients with presumed antibiotic-associated diarrhea susceptible to pseudomembranous colitis. This study was designed to determine the clinical risk factors for pseudomembranous colitis among the patients with presumed antibiotic-associated diarrhea. Methods: This was a retrospective study of 150 consecutive patients admitted to our institution between January 2000 and December 2004 with a diagnosis of presumed antibiotic-associated diarrhea. All patients underwent sigmoidoscopy or colonoscopy because of diarrhea after administration of antibiotics. Pseudomembranous colitis was confirmed both endoscopically and histologically. Various clinical parameters were compared between the pseudomembranous colitis group and non-pseudomembranous colitis group. Results: The mean age of patients was 61 years, and 60 percent (90/150) was female. Pseudomembranous colitis was diagnosed in 53 percent (80/150). On univariate analysis, older than aged 70 years (P=0.014), antibiotic therapy for more than 15 days (P<0.0001), hospital stay for more than 20 days (P<0.0001), number of antibiotics used more than one (P=0.01), and surgical procedures (P=0.029) were significant parameters for pseudomembranous colitis. On multivariate analysis, the important clinical risk factors were advanced age (older than aged 70 years; adjusted odds ratio, 2.7; 95 percent confidence interval, 1.208-6.131; P<0.016) and long hospital stay (more than 20 days; adjusted odds ratio, 5.1; 95 percent confidence interval, 2.1-12.259; P<0.0001). When both risk factors were present, the positive predictive value of pseudomembranous colitis was 0.86. Conclusions: Advanced age and long hospital stay may make patients with presumed antibiotic-associated diarrhea susceptible to pseudomembranous colitis. Therefore, pseudomembranous colitis should be first suspected in cases with presumed antibiotic-associated diarrhea having such risk factors.