title: Optimization of a Scoring System to Predict Microscopic Colitis in a Cohort of Patients With Chronic Diarrhea.
abstract: OBJECTIVE
  Our aim was to develop a scoring system to predict risk of microscopic colitis (MC), to identify patients at low risk, potentially avoiding unnecessary biopsies.
  
  
  BACKGROUND
  Patients with chronic diarrhea often undergo colonoscopy with biopsy, but few have histologic abnormalities.
  
  
  METHODS
  We conducted a retrospective study of patients with chronic diarrhea and a macroscopically normal colonoscopy at our institution over a 9-month period. Multivariable logistic regression assessed the association between predictors and the presence of biopsy-proven MC.
  
  
  RESULTS
  The derivation cohort included 617 patients. Median age was 55.1 (39.6 to 68.1) years; 397 (64.3%) were female and 81 (13.1%) had MC. Age ≥55 years, duration of diarrhea ≤6 months, ≥5 bowel movements per day, body mass index <30 kg/m, current smoking, and current use of selective serotonin reuptake inhibitors/serotonin-norepinephrine reuptake inhibitorss and non-steroidal anti-inflammatory drugs were independently associated with MC. A score of ≥10 points in our scoring system, yielded an area under the ROC curve (AUC) of 0.83 with a sensitivity of 93% and specificity of 49% in predicting which patients have MC. The negative predictive value (NPV) was 97.8% (95.0% to 99.1%).In the validation cohort, the scoring system performed similarly (AUC 0.79, sensitivity 91%, specificity 49%, NPV 97%). By avoiding biopsies in patients at low risk of having MC, costs associated with colon biopsies could be reduced by almost 43%.
  
  
  CONCLUSIONS
  This scoring system including 7 clinical variables was able to identify patients unlikely to have MC, with excellent sensitivity, reasonable specificity, and a high NPV, translating into important potential cost savings.
authors.affiliation: *Department of Internal Medicine †Mayo Clinic College of Medicine Divisions of ‡Anatomic Pathology §Gastroenterology and Hepatology, Mayo Clinic, Rochester, MN.
authors.forename: Thomas G
authors.initials: TG
authors.lastname: Cotter
authors.forename: Moritz
authors.initials: M
authors.lastname: Binder
authors.forename: Eugene P
authors.initials: EP
authors.lastname: Harper
authors.forename: Thomas C
authors.initials: TC
authors.lastname: Smyrk
authors.forename: Darrell S
authors.initials: DS
authors.lastname: Pardi
mesh_terms: D000328:Adult; D000368:Aged; D002908:Chronic Disease; D015331:Cohort Studies; D046728:Colitis, Microscopic / Q000145:classification / Q000175:diagnosis* / Q000473:pathology; D003106:Colon / Q000473:pathology*; D003113:Colonoscopy / Q000379:methods; D003661:Decision Support Techniques; D003967:Diarrhea; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012044:Regression Analysis; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index