Colorectal Disease: What FIT Threshold Should You Be Using?

Dawn O'Shea

July 30, 2020

A faecal immunochemical testing (FIT) threshold of ≥10 µg Hb/g faeces is appropriate to triage adult patients presenting to primary care with symptoms of serious colorectal disease, according to a study by researchers at Oxford University.

The study, published in Alimentary Pharmacology & Therapeutics, analysed faecal samples from routine primary care practice in Oxfordshire, between March 2017 and March 2020. Patients were followed up for up to 36 months in linked hospital records for evidence of benign and serious colorectal disease.

In 9896 adult patients with at least six-month follow-up, a FIT result ≥10 µg Hb/g faeces had a sensitivity for colorectal cancer of 90.5% (95% CI, 84.9%-96.1%), specificity of 91.3% (95% CI, 90.8%-91.9%), positive predictive value (PPV) of 10.1% (95% CI, 8.15%-12.0%) and negative predictive value (NPV) of 99.9% (95% CI, 99.8%-100.0%).

The PPV and specificity for serious colorectal disease were higher, but the sensitivity and NPV were lower than for colorectal cancer alone.

Using ≥10 µg Hb/g faeces, 10% of adults would be investigated to detect 91% of cancers, a number needed to scope of 10 to detect one cancer.

Using ≥7, ≥50 and ≥150 µg Hb/g faeces, 11 per cent, 4 per cent and 3 per cent of adults would be investigated, and 91, 74 and 54 cancers detected, respectively.

The authors concluded that a threshold of ≥10 µg Hb/g faeces could appropriately triage patients presenting to primary care with symptoms of serious colorectal disease.

The authors also suggest that FIT may be used to reprioritise patients referred with colorectal cancer symptoms whose investigations have been delayed by the COVID-19 pandemic.

Nicholson BD, James T, Paddon M, Justice S, Oke JL, East JE, Shine B. Faecal immunochemical testing for adults with symptoms of colorectal cancer attending English primary care: a retrospective cohort study of 14 487 consecutive test requests. Aliment Pharmacol Ther. 2020 Jul 17 [Epub ahead of print]. doi: 10.1111/apt.15969. PMID: 32677733 Full text.

This article originally appeared on Univadis, part of the Medscape Professional Network.


Comments on Medscape are moderated and should be professional in tone and on topic. You must declare any conflicts of interest related to your comments and responses. Please see our Commenting Guide for further information. We reserve the right to remove posts at our sole discretion.
Post as: