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

• Published in: Cancer epidemiology, biomarkers & prevention biomarkers & prevention, 2018-06, Vol.27 (6), p.704-709
• Main Authors: Chen, Sam Li-Sheng, Hsu, Chen-Yang, Yen, Amy Ming-Fang, Young, Graeme P, Chiu, Sherry Yueh-Hsia, Fann, Jean Ching-Yuan, Lee, Yi-Chia, Chiu, Han-Mo, Chiou, Shu-Ti, Chen, Hsiu-Hsi
• Format: Article
• Language: English
• Subjects: Accuracy; Age; Bioindicators; Cancer screening; Colon; Colonoscopy; Colorectal cancer; Colorectal carcinoma; Epidemiology; Feces; Hemoglobin; Males; Medical screening; Population characteristics; Sensitivity; Sex differences; Thresholds; Working conditions; Workloads
• ISSN: 1055-9965; 1538-7755
• DOI: 10.1158/1055-9965.EPI-17-0387

Despite age and sex differences in fecal hemoglobin (f-Hb) concentrations, most fecal immunochemical test (FIT) screening programs use population-average cut-points for test positivity. The impact of age/sex-specific threshold on FIT accuracy and colonoscopy demand for colorectal cancer screening are unknown. Using data from 723,113 participants enrolled in a Taiwanese population-based colorectal cancer screening with single FIT between 2004 and 2009, sensitivity and specificity were estimated for various f-Hb thresholds for test positivity. This included estimates based on a "universal" threshold, receiver-operating-characteristic curve-derived threshold, targeted sensitivity, targeted false-positive rate, and a colonoscopy-capacity-adjusted method integrating colonoscopy workload with and without age/sex adjustments. Optimal age/sex-specific thresholds were found to be equal to or lower than the universal 20 μg Hb/g threshold. For older males, a higher threshold (24 μg Hb/g) was identified using a 5% false-positive rate. Importantly, a nonlinear relationship was observed between sensitivity and colonoscopy workload with workload rising disproportionately to sensitivity at 16 μg Hb/g. At this "colonoscopy-capacity-adjusted" threshold, the test positivity (colonoscopy workload) was 4.67% and sensitivity was 79.5%, compared with a lower 4.0% workload and a lower 78.7% sensitivity using 20 μg Hb/g. When constrained on capacity, age/sex-adjusted estimates were generally lower. However, optimizing age/-sex-adjusted thresholds increased colonoscopy demand across models by 17% or greater compared with a universal threshold. Age/sex-specific thresholds improve FIT accuracy with modest increases in colonoscopy demand. Colonoscopy-capacity-adjusted and age/sex-specific f-Hb thresholds may be useful in optimizing individual screening programs based on detection accuracy, population characteristics, and clinical capacity. .