title: Diagnostic accuracy of point-of-care fecal calprotectin and immunochemical occult blood tests for diagnosis of organic bowel disease in primary care: the Cost-Effectiveness of a Decision Rule for Abdominal Complaints in Primary Care (CEDAR) study.
abstract: BACKGROUND
  Fecal biomarker tests that differentiate between organic bowel disease (OBD) and non-OBD in primary care patients with persistent lower-abdomen complaints could reduce the number of unnecessary referrals for endoscopy. We quantified the accuracy of fecal calprotectin and immunochemical occult blood (iFOBT) point-of-care (POC) tests and a calprotectin ELISA in primary care patients with suspected OBD.
  
  
  METHODS
  We performed biomarker tests on fecal samples from 386 patients with lower-abdomen complaints suggestive for OBD. Endoscopic and histological diagnosis served as reference.
  
  
  RESULTS
  OBD was diagnosed in 99 patients (prevalence 25.9%); 19 had adenocarcinoma, 53 adenoma, and 27 inflammatory bowel disease. Sensitivity for OBD was 0.64 (95% CI 0.54-0.72) for calprotectin POC, 0.56 (0.46-0.66) for iFOBT POC, and 0.74 (0.65-0.82) for calprotectin ELISA; specificities were 0.53 (0.48-0.59), 0.83 (0.78-0.87), and 0.47 (0.41-0.53), respectively. Negative predictive values (NPVs) were 0.81 (0.74-0.86), 0.85 (0.80-0.88), and 0.84 (0.78-0.89); positive predictive values (PPVs) varied from 0.32 (0.26-0.39) and 0.33 (0.27-0.39) (calprotectin tests) to 0.53 (0.44-0.63) (iFOBT POC). Combining the 2 POC tests improved sensitivity [0.79 (0.69-0.86)] and NPV [0.87 (0.81-0.91)] but lowered specificity [0.49 (0.44-0.55)] and PPV [0.35 (0.29-0.42)]. When adenomas ≤1 cm were considered non-OBD, the NPV of all tests improved to >0.90 [combined POC tests, 0.97 (0.93-0.99)].
  
  
  CONCLUSIONS
  Diagnostic accuracy of the tests alone or combined was insufficient when all adenomas were considered OBD. When only adenomas >1 cm were considered OBD, all tests could rule out OBD to a reasonable extent, particularly the combined POC tests. The tests were less useful for inclusion of OBD.
authors.affiliation: Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht, the Netherlands. l.kok-2@umcutrecht.nl
authors.forename: Liselotte
authors.initials: L
authors.lastname: Kok
authors.forename: Sjoerd G
authors.initials: SG
authors.lastname: Elias
authors.forename: Ben J M
authors.initials: BJ
authors.lastname: Witteman
authors.forename: Jelle G
authors.initials: JG
authors.lastname: Goedhard
authors.forename: Jean W M
authors.initials: JW
authors.lastname: Muris
authors.forename: Karel G M
authors.initials: KG
authors.lastname: Moons
authors.forename: Niek J
authors.initials: NJ
authors.lastname: de Wit
mesh_terms: D000230:Adenocarcinoma / Q000175:diagnosis; D000236:Adenoma / Q000175:diagnosis; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000032:analysis; D003430:Cross-Sectional Studies; D004238:Diverticulitis / Q000175:diagnosis; D004797:Enzyme-Linked Immunosorbent Assay; D005243:Feces / Q000737:chemistry*; D005260:Female; D058006:General Practice; D006801:Humans; D015212:Inflammatory Bowel Diseases / Q000175:diagnosis; D007410:Intestinal Diseases / Q000175:diagnosis*; D007414:Intestinal Neoplasms / Q000175:diagnosis; D039841:Leukocyte L1 Antigen Complex / Q000032:analysis*; D008297:Male; D008875:Middle Aged; D009780:Occult Blood; D019095:Point-of-Care Systems; D011320:Primary Health Care; D011349:Proctitis / Q000175:diagnosis; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D055815:Young Adult
chemical_list: D015415:Biomarkers; D039841:Leukocyte L1 Antigen Complex