FAECAL IMMUNOCHEMICAL TEST CHARACTERISTICS IN A 2 WEEK REFERRAL PATHWAY: A RELIABLE GATEKEEPER

ABSTRACT

Introduction Faecal Immunochemical testing (FIT) has become an important part of colorectal cancer referral pathways over the last few years. Implementation has been expediated by the Covid pandemic. FIT is increasingly used in primary care in conjunction with high risk symptoms and anaemia to direct referral for further investigation. This investigates the outcomes of patients referred to a large NHS Trust on a lower GI two week wait pathway and compares outcomes in those with and without an initial FIT test. Methods A total of 363 patients were from 1st to 28th February 2021, with information and result gathered from clinic letters and Trust IT systems. The FIT test result was recorded where it had been performed. Positive predictive value (PPV) and negative predictive value (NPV) were calculated to asses FIT performance and outcomes were stratified by FIT positivity. Results The majority of patients referred (275 of 363 patients or 75.54%) underwent FIT as part of their lower GI pathway referral. More than half had a positive FIT result of 10 7ug/ ml or greater (176/275, 64%). 14 out of 275 patients (5.09%) were found to have colorectal cancer. The overall PPV of FIT was 7.8%. PPV was higher in those with FIT >400 (38.5%). The PPV in those with FIT 10-49 was relatively low at 6.5% (5/91). Among 99 patients with negative FIT, 2 patients (2.0%) were found to have colorectal cancer, giving FIT a high NPV of 98.88%. Both patients presented with symptoms including weight loss (but no anaemia) and were diagnosed on CT imaging. Both had extensive metastatic disease at diagnosis. In the group who had not undergone FIT testing, 7 out of 88 (8.0%) were found to have cancer. Conclusions The majority of the patients referred had FIT initially, although continuous improvement is still needed to achieve the aim of all patients undergoing FIT prior to referral. The considerably higher PPV of FIT >400 compared to 10-49 demonstrates how the FIT value can be used to prioritise appropriate investigations and urgency to those with the highest diagnostic yield. As part of a lower GI pathway, there were two FIT negative cancers but these were both picked up on CT scans due to the associated presence of weight loss at presentation. This should reassure referrers that FIT negative patients without anaemia or weight loss do not need urgent referral.