Diagnostic accuracy of point of care faecal immunochemical testing using a portable high-speed quantitative analyser for diagnosis in two-week wait patients.

Maclean, William; Mackenzie, Paul; Limb, Chris; Zahoor, Zahida; Whyte, Martin B; Rockall, Timothy; Benton, Sally C; Jourdan, Iain

BACKGROUND Laboratory-based Faecal Immunochemical Testing (FIT) is the gold standard for detecting the presence of blood in the stool. AIM To perform a diagnostic accuracy study to confirm if a point of care (POC) analyser for FIT could be safely used as an adjunct in the triage and management of two-week wait (TWW) colorectal patients. DESIGN The "POC FIT" prospective observational cohort study was designed for TWW patients at a regional referral centre. Between July 2019 and March 2020, patients were invited to perform and bring a FIT sample to clinic. FIT was completed within the clinic appointment using a POC quantitative analyser that has a two-minute processing time (QuikRead go®). Patients and clinicians were blinded to results within the clinic appointment. The results were compared with subsequent diagnostic outcomes. Faecal haemoglobin <10 μg haemoglobin/g of faeces was considered a negative result. Sensitivities for colorectal cancer (CRC) and combined serious bowel disease (SBD) were calculated using this pre-determined cut-off. RESULTS 553 patients were included for analytical comparison with diagnostic outcomes. There were 14 (2.5%) patients with CRC and 52 (9.4%) with SBD. The sensitivities for CRC and SBD were 92.9% (95% Confidence Interval (CI): 68.5-98.7%) and 76.9% (CI:63.9-86.3%) respectively. 379 (68.5%) patients had a negative FIT result (negative predictive value for CRC was 99.7%) CONCLUSIONS: POC FIT is a useful adjunct to better manage TWW patients. The high observed sensitivity for CRC offers opportunities, within a single consultation, for improved triage and rationalisation of investigation for those with bowel symptoms.