This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Medicine
In case of acute severe colitis on day 3 of hospital , the best predictor of colectomy is: 
Select and explain. 
A. CRP > 45 mg/L and 3-8 stool frequency, B. ESR > 60 mm Hg and abdominal pain, C. Bleeding PR and abdominal distention, D. Tachycardia and fever
A: CRP > 45 mg/L and 3-8 stool frequency
Answer: A: CRP > 45 mg/L and 3-8 stool frequency 
Explanation: C-reactive protein is a less good marker for assessing disease activity in UC than Crohn's disease. In acute severe colitis a raised CRP > 45 mg/L on day 3 following hospital admission together with 3-8 stools a day is highly predictive for colectomy. Ref: Journal of Crohn's and Colitis (2012) 6, 965-990.