Unsatisfactory Fecal Immunochemical Tests for Colorectal Cancer Screening: Prevalence, Reasons, and Subsequent Testing

Abstract Background: Fecal immunochemical test (FIT) is an effective colorectal cancer screening modality. Little is known about prevalence, reasons, and testing after unsatisfactory FIT, or a FIT that cannot be processed by the laboratory due to inadequate stool specimen or incomplete labeling. Methods: Our retrospective cohort study examined unsatisfactory FIT among average-risk individuals aged 50–74 years in a large, integrated, safety-net health system who completed an index FIT from 2010 to 2019. We determined prevalence of unsatisfactory FIT and categorized reasons hierarchically. We used multivariable logistic regression models to identify factors associated with: (i) unsatisfactory FIT; and (ii) subsequent testing within 15 months of the unsatisfactory FIT. Results: Of 56,980 individuals completing an index FIT, 10.2% had an unsatisfactory FIT. Reasons included inadequate specimen (51%), incomplete labeling (27%), old specimen (13%), and broken/leaking container (8%). Unsatisfactory FIT was associated with being male [OR,1.10; confidence interval (CI), 1.03–1.16], Black (OR, 1.46; CI, 1.33–1.61), Spanish speaking (OR, 1.12; CI, 1.01–1.24), on Medicaid (OR, 1.42; CI, 1.28–1.58), and received FIT by mail (OR, 2.66; CI, 2.35–3.01). Among those with an unsatisfactory FIT, fewer than half (41%) completed a subsequent test within 15 months (median, 4.4 months). Adults aged 50–54 years (OR, 1.16; CI, 1.01–1.39) and those who received FIT by mail (OR, 1.92; CI, 1.49–2.09) were more likely to complete a subsequent test. Conclusions: One in ten returned a FIT that could not be processed, mostly due to patient-related reasons. Fewer than half completed a subsequent test after unsatisfactory FIT. Impact: Screening programs should address these breakdowns such as specimen collection and labeling to improve real-world effectiveness.