An analysis of the duplicate testing strategy of an Irish immunochemical FOBT colorectal cancer screening programme.

Abstract

AIM: This study examined the relevance of using a two sample quantitative immunochemical faecal occult blood test (iFOBT or FIT) at a high cut off stringency by the first population-based colorectal cancer (CRC) pilot screening programme in Ireland. METHOD: Approximately ten thousand individuals between the ages of 50-74 years were invited to perform two consecutive FITs. These were analysed in tandem using the OC-Sensor and participants with at least one positive result with a haemoglobin cut off for positivity at 100 ng/ml were offered colonoscopy. RESULTS: A total of 5023 (52%) (2177 (43%) male; 2846 (57%) female) individuals with a median age of 64 years participated. At least one positive FIT test was detected from 514 (10%) individuals. From the 419 (82%) patients who proceeded to colonoscopy 17 (4%) had CRC and 132(33%) had an advanced adenoma. The detection rate for these screen relevant lesions was 3% (95% CIs = 2.5% - 3.5%) and the FIT positive + colonoscopy detection rate was 36% (95% CI = 31% - 40%). The numbers needed to colonoscope to find an advanced lesion was 2.8. The two test system detected four (23.5%) additional patients with CRC and 37 (28%) with an advanced adenoma compared with a single test. CONCLUSION: The CRC miss rate estimated for a single test (23.5%) was unacceptably high when the goal was to maximize the discovery of advanced lesions in the initial screening round. We conclude that the two test protocol at a high cut off threshold is suitable to optimize FIT screening in Ireland. This article is protected by copyright. All rights reserved.