Does FIT have a role in the detection of small bowel pathology: a prospective study

The faecal immunochemical test (FIT) is an immunoassay used to detect human blood in the stool. The role of FIT as a screening tool for small bowel pathology remains unclear.

This study aimed to investigate the role of FIT in predicting small bowel pathology in patients with iron deficiency anaemia (IDA).

This was a single tertiary centre prospective study. The inclusion criterion was adults (⩾18 years and <80 years) with IDA who were referred to secondary care for endoscopic investigations.

All patients had a FIT test done in primary care. Eligible patients were invited to have a small bowel capsule endoscopy (SBCE) prior to endoscopy. Patients with subsequent upper or lower gastrointestinal tract malignancy were excluded from the study. IDA was defined as a Hb < 131 g/L for men and <110 g/L for women with ferritin <30 µg/L and/or iron levels <11 µmol/L. A further 100 patients with recurrent/refractory IDA who did not have a FIT test done and had an SBCE were used as the control group.

In total 179 patients were included in the final analysis with a median age of 64.5 years (interquartile range (IQR 51-75)); haemoglobin 101 (IQR 90-111) and ferritin 11(7-20). In the prospective FIT group of 79 patients, there were 35 (44%) patients with significant findings on SBCE which was classed as contributing to IDA. These findings included angioectasia in n = 21 (26.6%) patients which was the most common finding. The other findings included erosions and ulcers = 5 (7.6%); inflammatory strictures = 3 (3.8%); active Crohn's n = 1 (1.3%); visible blood with no clear source n = 3 (3.8%) and bleeding angioectasia n = 1 (1.3%). A positive FIT (>10) had a sensitivity, specificity, positive predictive value and negative predictive value of 34.29%, 54.55%, 37.5% and 51.08%, respectively. In the control group (n = 100), 37% of the patients had significant pathology on SBCE. On logistic regression, age (OR 1.06; 95% CI: 1.03-1.11) was the only factor related to the probability of having a positive finding on SBCE.

Over a third of the patients with IDA have significant findings on SBCE. However, in this study, we did not find that FIT conferred any additional benefit in the detection of small bowel pathology.