Patient selection: adult >= 18 years of age upon completion of therapy for Clostridium difficile disease, excluding Clostridium difficile disease in the previous 3 months
Risk factors for recurrence:
(1) female gender (hazard ratio 1.6)
(2) older age
(3) lymphopenia (absolute lymphocyte count < 1,000 per µL) after completing Clostridium difficile therapy (hazard ratio 2.2)
(4) negative Clostridium difficile anti-toxin serology
where:
• A positive C. difficile anti-toxin serology was protective (hazard ratio 0.17).
• While enrollment was age >= 18 years, most patients were older with mean age 77 years and first quartile 65 years. The hazard ratio is given as 2.26 per decade. The starting point for this risk is not stated. It may start at 60 (relative). This would give the risk of someone 80 years old 5.1; if taken from date of birth (absolute) the hazard ratio would be 2.26^8 = 680.
• Lymphopenia may be a marker of immunodeficiency and/or malnutrition (see Instant Nutritional Assessment and Protein Energy Malnutrition Scale in Chapter 12).
• History of recurrent infection would probably be a risk factor but this group would have been excluded.
