Combining faecal immunochemical testing with blood test results for colorectal cancer risk stratification: a consecutive cohort of 16,604 patients presenting to primary care

• Published in: BMC medicine Vol. 20; no. 1; p. 116
• Main Authors: Withrow, Diana R, Shine, Brian, Oke, Jason, Tamm, Andres, James, Tim, Morris, Eva, Davies, Jim, Harris, Steve, East, James E, Nicholson, Brian D
• Format: Journal Article
• Language: English
• Published: England BioMed Central Ltd 15.03.2022; BioMed Central; BMC
• Subjects: Blood; Cancer; Colonoscopy - methods; Colorectal cancer; Colorectal neoplasms; Colorectal Neoplasms - diagnosis; Colorectal Neoplasms - epidemiology; Development and progression; Diagnosis; Early Detection of Cancer - methods; Faecal immunochemical tests; Full blood count; Humans; Medical examination; Occult Blood; Oncology, Experimental; Predictive value of tests; Primary Health Care; Risk factors; Triage; United Kingdom; Triage; Colorectal neoplasms; Faecal immunochemical tests; Primary health care; Predictive value of tests; Full blood count
• ISSN: 1741-7015; 1741-7015
• DOI: 10.1186/s12916-022-02272-w

Faecal immunochemical tests (FITs) are used to triage primary care patients with symptoms that could be caused by colorectal cancer for referral to colonoscopy. The aim of this study was to determine whether combining FIT with routine blood test results could improve the performance of FIT in the primary care setting. Results of all consecutive FITs requested by primary care providers between March 2017 and December 2020 were retrieved from the Oxford University Hospitals NHS Foundation Trust. Demographic factors (age, sex), reason for referral, and results of blood tests within 90 days were also retrieved. Patients were followed up for incident colorectal cancer in linked hospital records. The sensitivity, specificity, positive and negative predictive values of FIT alone, FIT paired with blood test results, and several multivariable FIT models, were compared. One hundred thirty-nine colorectal cancers were diagnosed (0.8%). Sensitivity and specificity of FIT alone at a threshold of 10 μg Hb/g were 92.1 and 91.5% respectively. Compared to FIT alone, blood test results did not improve the performance of FIT. Pairing blood test results with FIT increased specificity but decreased sensitivity. Multivariable models including blood tests performed similarly to FIT alone. FIT is a highly sensitive tool for identifying higher risk individuals presenting to primary care with lower risk symptoms. Combining blood test results with FIT does not appear to lead to better discrimination for colorectal cancer than using FIT alone.