title: Fecal occult blood test in patients on low-dose aspirin, warfarin, clopidogrel, or non-steroidal anti-inflammatory drugs.
abstract: OBJECTIVE
  To determine the effect of anticoagulants and antiplatelet medications on the positive-predictive-value of fecal occult blood test (FOBT).
  
  
  METHODS
  All patients who underwent a colonoscopy at our institution from 1995 to 2006 for a positive FOBT were identified. Medical records were searched, and patients were stratified into five groups selected a priori: low-dose aspirin, NSAIDs, warfarin, clopidogrel, or controls. The positive-predictive-value of FOBT for advanced colonic neoplasia was computed for each group.
  
  
  RESULTS
  During the study period, 1,126 patients underwent colonoscopy for a positive FOBT and met entry criteria. The average age of study participants was 69 years and most were men. The positive-predictive-value of FOBT for advanced colon neoplasia was significantly higher in the control group (30.5%) when compared to those on low-dose aspirin (20.5%; p = 0.003), NSAIDs (19.7%; p = 0.003), clopidogrel (7.3%; p = 0.002), or warfarin (20%; p = 0.05). The positive-predictive-value of FOBT was significantly lower for those on clopidogrel than those on low-dose aspirin (p = 0.04) and NSAIDs (p = 0.05), but not warfarin (p = 0.08). The positive-predictive-value for FOBT was similar for those on aspirin, NSAIDs, and warfarin. There was a linear trend between the number of number of positive FOBT cards and prevalence of advanced colon neoplasia (p = 0.01).
  
  
  CONCLUSIONS
  Anticoagulants and antiplatelet medications lower the positive-predictive-value of FOBT for advance colonic neoplasia and should be stopped if clinically feasible prior to stool collection.
authors.affiliation: Division of Gastroenterology, Minneapolis Veterans Affairs Medical Center, Minneapolis, MN, USA. msawhney@bidmc.harvard.edu
authors.forename: Mandeep S
authors.initials: MS
authors.lastname: Sawhney
authors.forename: Heather
authors.initials: H
authors.lastname: McDougall
authors.forename: Douglas B
authors.initials: DB
authors.lastname: Nelson
authors.forename: John H
authors.initials: JH
authors.lastname: Bond
mesh_terms: D000368:Aged; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000008:administration & dosage / Q000009:adverse effects*; D000925:Anticoagulants / Q000008:administration & dosage / Q000009:adverse effects*; D001241:Aspirin / Q000008:administration & dosage / Q000009:adverse effects*; D000077144:Clopidogrel; D003110:Colonic Neoplasms / Q000175:diagnosis*; D003113:Colonoscopy; D005260:Female; D006471:Gastrointestinal Hemorrhage / Q000139:chemically induced / Q000175:diagnosis; D006801:Humans; D016015:Logistic Models; D008297:Male; D008403:Mass Screening / Q000379:methods*; D008875:Middle Aged; D009780:Occult Blood; D016017:Odds Ratio; D010975:Platelet Aggregation Inhibitors / Q000008:administration & dosage / Q000009:adverse effects*; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D013988:Ticlopidine / Q000008:administration & dosage / Q000009:adverse effects / Q000031:analogs & derivatives*; D019564:Unnecessary Procedures; D014859:Warfarin / Q000008:administration & dosage / Q000009:adverse effects*
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D000925:Anticoagulants; D010975:Platelet Aggregation Inhibitors; D014859:Warfarin; D000077144:Clopidogrel; D013988:Ticlopidine; D001241:Aspirin