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

摘要

BACKGROUND: Fecal biomarker tests that differentiate between organic bowel disease (OBD) and non-OBD in primary care patients with persistent lowerabdomen 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.