A New-Generation Fecal Immunochemical Test (FIT) Is Superior to Quaiac-based Test in Detecting Colorectal Neoplasia Among Colonoscopy Referral Patients

Abstract

Aim: To compare a new-generation fecal immunochemical test (FIT) with the leading guaiac-based test in detection of fecal occult blood (FOB) in colonoscopy-referral patients.

Patients and methods: A cohort of 300 patients referred for colonoscopy was examined by two different tests for FOB: ColonView quick test (CV) (FIT test for haemoglobin (Hb) and haemoglobin/haptoglobin (Hb/Hp) complex) and HemoccultSENSA (HS) (quaiac test for Hb). Three fecal samples were tested and all subjects were examined by diagnostic colonoscopy with biopsy verification. The test was interpreted positive if any of the three samples tested positive for Hb (HS test) and either Hb or Hb/Hp complex (CV test). The performance indicators (sensitivity (SE), specificity (SP), positive predictive value (PPV), negative predictive value (NPV) and area under the curve (AUC)) were calculated for both tests using three endpoints (adenoma (A), adenoma/carcinoma (A/AC) and carcinoma (AC)), collectively and were stratified according to tumor site. The two tests were compared regarding their sensitivity/specificity balance (AUC), using the receiver operating characteristics (ROC) comparison test.

Results: Colonoscopy (and biopsies) disclosed normal results in 85 (27.2%) subjects, A in 91 cases (30.3%) and AC in 95 (31.7%) patients. For the combined A+AC endpoint, the HS test had SE of 58.3% and SP of 96.5% (AUC=0.774), while the CV test had 97.2% SE and 85.8% SP (AUC=0.916) (p=0.0001). For the A endpoint, the difference between HS and CV was even more significant, AUC=0.637 and AUC=0.898, respectively (p=0.0001). In CV test, the Hb/Hp complex was 15% (93% vs. 78%) and 8% (96% vs. 88%) more sensitive than Hb alone, for the A and A+AC endpoints, respectively. Being more stable than Hb in the feces, the Hb/Hp complex detected 100% of the tumors in the proximal colon, as contrasted to only 41.2% and 52.9% by the Hb of HS and CV test, respectively (p=0.0001).

Conclusions: With its 100% SE and 95.3% SP for proximal colon neoplasia, as well as 98.2% SE and 95.3% SP for the distal neoplasia, ColonView is superior to current FIT tests on the market, recently shown to exhibit pooled SE of 79% and pooled SP of 94% for colorectal cancer (CRC) in a comprehensive meta-analysis. With these exceptional performance indicators, ColonView quick test should be the test-of-choice for CRC screening.

Keywords: Colorectal cancer; R.O.C. analysis; fecal immunochemical test (FIT); fecal occult blood (FOB); performance; quaiac-based FOB test; screening.