{
  "abstract": "Introduction A faecal immunochemical test (FIT) threshold of ≥10 µg/g is currently used to determine the need for urgent investigation for suspected colorectal cancer (CRC). However, at this threshold the demand for colonoscopy or computed tomography colonography (CT-C) exceeds capacity. In London, approximately 70,000 patients per year are referred to the lower gastrointestinal (GI) urgent suspected cancer service. The COLOFIT model, incorporating FIT, age, sex and routine blood parameters, was recently developed to improve CRC risk stratification and therefore prioritisation of patients for urgent investigation. We aimed to externally validate the COLOFIT model in a multicentre secondary care setting among patients referred under an urgent suspected cancer pathway, comparing its diagnostic performance to FIT alone and assessing its potential to reduce the number of urgent referrals.Methods We performed a retrospective multi-centre cohort study of patients referred under lower GI urgent suspected cancer pathways to eight London hospitals between 2023 and 2025. Patients with all available COLOFIT variables (FIT, age, sex, platelet count and mean cell volume) and a confirmed CRC outcome were included. We evaluated the diagnostic performance of COLOFIT across a range of thresholds and compared it with FIT ≥10 µg/g. Discrimination was assessed using the area under the receiver operating characteristic curve (AUC).Results 2511 patients were included (median age 64 years and 47% male). 115 (4.6%) were diagnosed with CRC. Using FIT ≥10 µg/g, sensitivity for CRC was 95.7% (95% CI: 90.2– 98.6%) with a specificity of 19.5% (CI: 18.0–21.2%). We identified that a COLOFIT threshold of 0.75% 1-year CRC risk captured the same number of cancers as FIT ≥10 µg/g and would have led to a reduction in urgent referrals by 303 (12%). This COLOFIT threshold had a sensitivity of 95.7% (CI: 90.2–98.6%), a specificity of 32.2% (CI: 30.4–34.1%) and a negative predictive value of 99.4% (CI: 98.5–99.7%). The COLOFIT model demonstrated comparable discriminatory performance to FIT, with an AUC of 0.77 (CI: 0.72–0.81) compared to 0.74 (CI: 0.70–0.78, p = 0.052) for FIT.Conclusions Our study externally validates the COLOFIT model in patients urgently referred for suspected colorectal cancer. The COLOFIT model would lead to a reduction in urgent referrals by 12%. In London, this could lead to a reduction in around 8500 referrals per year to the urgent suspected cancer pathway. The COLOFIT model is a potential tool to lower urgent referral volume without increasing missed cancer risk.",
  "authors": [
    {
      "affiliations": [
        "University College London Hospitals NHS Foundation Trust, London, United Kingdom"
      ],
      "name": "Maura Morrison"
    },
    {
      "affiliations": [
        "University College London Hospitals NHS Foundation Trust, London, United Kingdom"
      ],
      "name": "Philippe Gerard"
    },
    {
      "affiliations": [
        "University College London Hospitals NHS Foundation Trust, London, United Kingdom"
      ],
      "name": "Omer F Ahmad"
    },
    {
      "affiliations": [
        "University College London Hospitals NHS Foundation Trust, London, United Kingdom"
      ],
      "name": "Sara McCartney"
    },
    {
      "affiliations": [
        "The Hillingdon Hospital NHS Foundation Trust, London, United Kingdom"
      ],
      "name": "Mahmoud El Khatib"
    },
    {
      "affiliations": [
        "The Hillingdon Hospital NHS Foundation Trust, London, United Kingdom"
      ],
      "name": "Alistair Myers"
    },
    {
      "affiliations": [
        "Chelsea and Westminster Hospital NHS Foundation Trust, London, United Kingdom"
      ],
      "name": "Martina Cusack"
    },
    {
      "affiliations": [
        "London North West University Healthcare NHS Trust, London, United Kingdom"
      ],
      "name": "Aurelia Wawszczak"
    },
    {
      "affiliations": [
        "Imperial College Healthcare NHS Trust, London, United Kingdom"
      ],
      "name": "Paul Ziprin"
    },
    {
      "affiliations": [
        "Kingston and Richmond NHS Foundation Trust, London, United Kingdom"
      ],
      "name": "Joshua Artezuela"
    },
    {
      "affiliations": [
        "Nottingham University Hospitals NHS Trust, Nottingham, United Kingdom"
      ],
      "name": "David Humes"
    },
    {
      "affiliations": [
        "University College London Hospitals NHS Foundation Trust, London, United Kingdom"
      ],
      "name": "Edward Seward"
    }
  ],
  "title": "O3 The COLOFIT model for triage of urgent colorectal cancer referrals: a multi-centre study",
  "uid": "960680c1-59f2-55af-bc5b-e0790f799ed9"
}