Abstract
BackgroundThe fecal immunochemical test (FIT) is easier to use and more sensitive than the guaiac fecal occult blood test, but it is unclear how to optimize FIT performance. We compared the sensitivity and specificity for detecting advanced colorectal neoplasia between single-sample (1-FIT) and two-sample (2-FIT) FIT protocols at a range of hemoglobin concentration cutoffs for a positive test.MethodsWe recruited 2,761 average-risk men and women ages 49-75 referred for colonoscopy within a large nonprofit, group-model health maintenance organization (HMO), and asked them to complete two separate single-sample FITs. We generated receiver-operating characteristic (ROC) curves to compare sensitivity and specificity estimates for 1-FIT and 2-FIT protocols among those who completed both FIT kits and colonoscopy. We similarly compared sensitivity and specificity between hemoglobin concentration cutoffs for a single-sample FIT.ResultsDifferences in sensitivity and specificity between the 1-FIT and 2-FIT protocols were not statistically significant at any of the pre-specified hemoglobin concentration cutoffs (10, 15, 20, 25, and 30 μg/g). There was a significant difference in test performance of the one-sample FIT between 50 ng/ml (10 μg/g) and each of the higher pre-specified cutoffs. Disease prevalence was low.ConclusionsA two-sample FIT is not superior to a one-sample FIT in detection of advanced adenomas; the one-sample FIT at a hemoglobin concentration cutoff of 50 ng/ml (10 μg/g) is significantly more sensitive for advanced adenomas than at higher cutoffs. These findings apply to a population of younger, average-risk patients in a U.S. integrated care system with high rates of prior screening.
Highlights
The fecal immunochemical test (FIT) is easier to use and more sensitive than the guaiac fecal occult blood test, but it is unclear how to optimize FIT performance
Since 1996, Kaiser Permanente Northwest (KPNW) has maintained complete electronic medical records (EMRs) for each health plan member, and its administrative and clinical databases are available for research purposes; members provide consent to use their data for research purposes upon enrollment or can opt out
Number of colonoscopy-detected colorectal cancers among the referral cohort To further contextualize disease rates among individuals within the analytic cohort, we evaluated Colorectal cancer (CRC) incidence within the referral cohort that served as the initial recruitment source for participants in the study, utilizing electronic procedure codes and the Tumor Registry
Summary
The fecal immunochemical test (FIT) is easier to use and more sensitive than the guaiac fecal occult blood test, but it is unclear how to optimize FIT performance. Large trials comparing the effectiveness of colonoscopy with FIT use the OC-Auto-FIT (prior names: OC Micro, OC Sensor) [18, 19], a quantitative FIT with results processed by an automated analyzer. This FIT has been found to be 80% sensitive for cancer when used at the manufacturer-recommended hemoglobin concentration cutoff of 100 ng/ml of buffer, or 20 μg/g of stool [19, 20]. The sensitivity of the OC-Auto FIT can be increased further by lowering the cutoff of hemoglobin concentration for a positive test result [15], it has been unknown what the trade-off in false positives would be at a lower cutoff if used in an average-risk screening population
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