Advanced age (≥65), marked leukocytosis (leukocyte count >15 × 109/L), decreased blood albumin (<30 g/L), a rise in the serum creatinine level (≥133 μM or ≥1.5 times the premorbid level), and comorbidities (severe underlying disease and/or immunodeficiency) also should be regarded as poor prognostic markers for severe CDI7. Here, ALB is linked to Immunodeficiency.