Age <50 Years Does NOT Increase Risk of Clostridioides difficile Infection
The correct answer is B) Age <50 years - this is the only factor listed that does NOT increase CDI risk; in fact, younger age is protective, as advanced age is one of the most important risk factors for CDI.
Risk Factor Analysis Based on IDSA/SHEA Guidelines
According to the authoritative 2018 IDSA/SHEA guidelines 111, the established risk factors for CDI include:
Confirmed Risk Factors (Options A, C, D, E):
Advanced age is explicitly identified as "one of the most important risk factors for CDI" 11. The guidelines note that older age increases risk for both initial CDI and complicated disease with higher mortality 11.
Frailty with comorbidities (Option A): The guidelines specifically state that "risk factors for complicated disease include older age, leukocytosis, renal failure and comorbidities" 11. Comorbidities are consistently associated with increased CDI risk and mortality.
Immunosuppression/chemotherapy (Option C): The guidelines clearly state that "cancer chemotherapy is another risk factor for CDI" mediated by antibiotic activity and immunosuppressive effects of neutropenia 11. HIV-infected patients are at "specific increased risk because of their underlying immunosuppression" 1.
Inflammatory bowel disease (Option D): IBD is explicitly listed as a risk factor, with the guidelines noting that "low vitamin D levels being an independent risk factor among...those with underlying inflammatory bowel disease" 1. The 2020 Taiwan guidelines 22 also confirm IBD as a risk factor.
Proton pump inhibitors (Option E): While controversial, PPIs are discussed extensively as a potential risk factor. The guidelines note "a number of studies have suggested an epidemiologic association between use of stomach acid–suppressing medications, primarily PPIs, and CDI" 111. One study showed "continuous use of PPIs was independently associated with a 50% increased risk for recurrence" 11.
The Protective Factor (Option B):
Age <50 years is protective - the inverse relationship is what matters here. The guidelines consistently emphasize that advanced age increases risk, meaning younger age (<50 years) does NOT increase risk and actually provides relative protection 111.
Clinical Context for This Patient
Your 72-year-old patient has multiple CDI risk factors:
- Advanced age (72 years) - major risk factor
- Antibiotic exposure (ampicillin prior to admission, current antibiotics for pneumonia) - the most important modifiable risk factor 11
- Hospitalization - duration increases exposure risk 1
- Potential PPI use (common in hospitalized patients) - controversial but possible contributor
Key Clinical Pitfall
Don't be confused by the question format asking what does NOT increase risk. Age <50 is the outlier because it represents the absence of a risk factor (advanced age), making it the correct answer.