ID: 3526093 THE VALUE OF QUANTITATIVE FAECAL IMMUNOCHEMICAL TEST (QFIT) AS A PRIORITISATION TOOL FOR PATIENTS WITH IRON DEFICIENCY REQUIRING URGENT OUTPATIENT INVESTIGATION

Abstract

Difficulty in providing endoscopy for patients with iron deficiency anaemia (IDA) during the COVID-19 pandemic has highlighted the requirement for a prioritisation tool. Currently qFIT has a role in colorectal cancer screening and in identifying patient cohorts with colorectal symptoms who may benefit from more urgent endoscopy. We aimed to test the validity of qFIT as a prioritisation tool in patients with iron deficiency and its ability to identify patients with neoplasia, defined as upper GI cancer, colonic adenoma over 1cm or colorectal cancer. Data collected from patients referred with biochemically proven iron deficiency and synchronous qFIT who underwent full gastrointestinal investigation within NHS Greater Glasgow and Clyde was analysed retrospectively. Biochemically proven iron deficiency was defined as a ferritin ≤ 15 micrograms/L. Patients who did not undergo full investigation, defined as gastroscopy and colonoscopy or CT colonography, were excluded. Outcomes from these investigations were linked to qFIT results. Area under the curve (AUC) analysis was performed on qFIT results and outcome, defined as the presence of neoplasia. Sensitivity and specificity from AUC analysis guided cut-off scores for qFIT. Patients with a qFIT of <9, 10-200, >200, were allocated a score of 1, 2 and 3 respectively. A total of 575 patient met criteria for inclusion into the study. Within the patient cohort, 50 patients had a confirmed neoplasm. Overall, qFIT results strongly predicted the presence of GI neoplasms (AUC 0.866, 0.812-0.921; P <0.001). The prevalence of neoplasm in patients with scores 1 to 3 was 1.2%, 13.5% and 38.9% respectfully. When controlled for other significant variables, patients with a higher qFIT score were statistically more likely to have a GI neoplasm (qFIT score = 2; OR 12.8; P<0.001, qFIT score = 3, OR 50.0; P<0.001). qFIT was highly sensitive for the presence of neoplasia (92.0% (84.4%-99.5%), with moderate specificity (63.2% (59.1%-67.4%)). A negative qFIT had a high negative predictive value for the presence of neoplasia (98.5% 97.5%-100.0%). These results strongly suggest that qFIT has validity as a prognostic tool in patients with iron deficiency; both allowing for a more informed decision of investigation of patients with very low risk of malignancy, and in identifying higher risk patients who may benefit from more urgent endoscopy.