Cumulative evaluation of a quantitative immunochemical fecal occult blood test to determine its optimal clinical use

Abstract

BACKGROUND: Quantified, human hemoglobin (Hb)-specific, immunochemical fecal occult blood test (IFOBT) measurements are now used for colorectal cancer (CRC) screening. The objective was to evaluate sensitivity and specificity for CRC and advanced adenomatous polyps (APs) by the fecal Hb threshold used to determine a positive test and the number of IFOBTs prepared per test, so as to determine the least number of colonoscopies required to detect a neoplasm. METHODS: Cumulative data were analyzed from a prospective cross-sectional double-blind study of 1682 consecutive, ambulatory, nonbleeding colonoscopy patients who volunteered for IFOBTs, most of above average risk, from 3 ambulatory-endoscopy centers. Fecal Hb was measured in 3 samples and analyzed by an automated instrument, and the highest result !50 ng Hb/mL of buffer was related to findings. RESULTS: Colonoscopy identified CRC in 20 patients and advanced APs in 129. Sensitivity for either was best when any of 3 tests had !50 ng Hb/mL of buffer; sensitivity was 61.1% (95% confidence interval [CI], 53.2-68.9), and specificity was 87.8% (95% CI, 86.2-89.4). Positive tests identified 100% of CRCs and 55% of advanced APs every 3.1 colonoscopies. Sensitivity of a single test at the commonly used 100-ng Hb/mL threshold was lower at 31.5% (95% CI, 24.1-39.0) (P<.001), but specificity was higher at 96.4% (95% CI, 95.5-97.3) (P<.001). Positive tests identified 65% of CRCs and 26.4% of advanced APs every 2.2 colonoscopies. CONCLUSIONS: The fecal Hb cutoff chosen by the screener and the number of samples collected per patient determine sensitivity and specificity for CRC/advanced AP; these factors determine the number of colonoscopies needed for positive tests and neoplasia yield. This information provides guidelines for IFOBT screening. Limitations are 1-time screening and most examinees not being at average risk for CRC. Cancer 2010;116:2115-25.

Demand for Colonoscopy in Colorectal Cancer Screening Using a Quantitative Fecal Immunochemical Test and Age/Sex-Specific Thresholds for Test Positivity

“…Rozen et al found that for screening average-risk subjects 95% specificity for CRC was achieved by using a one-sample quantitative FIT with a 20 ug Hb/g threshold (21). Our study shows that the optimal threshold changes when considering age and sex.…”

Diagnostic accuracy of fecal immunochemical test in average‐ and familial‐risk colorectal cancer screening

“…These studies have shown that FIT is highly sensitive for detecting CRC, its accuracy for AN is adequate and it is a cost-effective test in the CRC screening setting. [20][21][22][23][24][25][26][27][28][29][30] However, no studies have compared the diagnostic accuracy between these populations of a quantitative FIT so far. Only one recently published study has compared the diagnostic yield of a qualitative FIT in these two populations, and the authors did not find differences in FIT yield either.…”

Fecal immunochemical test accuracy in familial risk colorectal cancer screening

“…15,23,30 In recent years, several published studies have analyzed FIT diagnostic accuracy in familial risk CRC screening, although none of them were specifically designed to assess it. [16][17][18][19]23,[30][31][32][33][34][35] Our study confirms previous data showing a high sensitivity and specificity for CRC at a 100 ng/ml positive threshold, reaching 100 and 90%, respectively. However, diagnostic accuracy for AN was lower in our study.…”