Optimal diagnostic accuracy of quantitative faecal immunochemical test positivity thresholds for colorectal cancer detection in primary health care: A community-based cohort study.

BACKGROUND: Optimizing colonoscopy resources is challenging, and information regarding performing diagnostic quantitative faecal immunochemical test (FIT) in daily clinical practice in primary health care is still limited. This study aimed to assess the sensitivity, specificity, positive predictive value and negative predictive value of varying FIT positivity thresholds on colorectal cancer (CRC) detection in primary health care. METHODS: A retrospective cohort study of 38,675 asymptomatic and symptomatic patients with a FIT (OC-Sensor™) performed between 2012 and 2016 in a primary health-care setting, using a clinical laboratory database of two Spanish areas linked with the National Health System's Hospital Discharge Records Database. The primary outcome was 2-year CRC incidence. RESULTS: The mean age of the participants was 63.2 years; 17,792 (46.0%) were male. CRC prevalence was 1.7% (650/38,675). The percentage of patients with a FIT result above the threshold was 20.7% and 14.6% for 10 µg Hb/g faeces and 20 µg Hb/g faeces thresholds, respectively. Sensitivity was 90.5% (95% confidence interval 88.0%-92.5%) at a 10 µg Hb/g faeces threshold, and this decreased by 3.1% when a 20 µg Hb/g faeces threshold was used. The negative predictive value for CRC was at least 99.2% in any subgroup analysed. At a 20 µg Hb/g faeces threshold, less than one additional CRC would be missed per 1000 patients investigated, while approximately 1.3 times more colonoscopy examinations were needed to identify an incidence of CRC using the lowest threshold for any situation analysed. CONCLUSIONS: In primary health care, a quantitative FIT threshold should be tailored to colonoscopy capacity and CRC prevalence in specific populations.

Colorectal Cancer Survival in 50- to 69-Year-Olds after Introducing the Faecal Immunochemical Test.

Population screening has improved early diagnosis of colorectal cancer (CRC). Nonetheless, most cases are diagnosed in symptomatic patients. Faecal immunochemical testing has been recommended for assessing patients with lower gastrointestinal symptoms, but whether it improves patient survival is unknown. Our objective was to compare CRC survival in 50- to 69-year-olds between asymptomatic screen-detected patients and symptomatic patients by route to diagnosis. METHODS: We identified all cases of CRC diagnosed in 50-to 69-year-olds between 2009 and 2016, in Donostialdea (Gipuzkoa, Spain). Three groups were created: 1-screen-detected CRC; 2-CRC detected in symptomatic patients after a positive faecal immunochemical test(FIT); and 3-CRC detected in symptomatic patients without a FIT or after a negative result. We analysed survival using the Kaplan-Meier method and log-rank tests. RESULTS: Of 930 patients diagnosed with CRC, 433 cases were detected through screening and 497 in symptomatic patients, 7.9% after a positive FIT and 45.5% by other means. The 3-year CRC survival was significantly lower in group 3 (69.5%) than groups 1 (93%; p = 0.007) or 2 (87.5%; p = 0.02). The risk of death was lower in groups 1 (HR 0.42, 95% CI 0.30-0.58) and 2 (HR 0.51; 95% CI 0.29-0.87). CONCLUSION: Half of CRC cases in 50- to 69-year-olds are diagnosed outside screening. Use of the FIT as a diagnostic strategy in symptomatic patients may improve survival.

Impact of the faecal immunochemical test on colorectal cancer survival.

BACKGROUND: There is already evidence that the faecal immunochemical test (FIT) is a useful tool for the diagnosis of colorectal cancer (CRC) that helps to identify symptomatic patients requiring early colonoscopy. Although the recommendation to use FIT is widely accepted, there are no data concerning whether this strategy improves patient survival.The objective was to assess whether the survival is higher if CRC patients have been first diagnosed by FIT (as compared with the rest of patients with CRC). METHODS: We identified all cases of CRC diagnosed between 2009 and 2016 in Donostialdea (Spain), excluding all the CRC detected in population screening. We focused on symptomatic patients. One thousand five hundred twenty-seven cases of CRC were divided into two groups based on the route to diagnosis: group 1: individuals who tested positive in a FIT during the year before diagnosis, and group 2: others.Survival was assessed by Kaplan-Meier estimation, and with the log-rank test. A Cox regression model was used to adjust for differences between groups due to other variables associated with survival. RESULTS: One thousand nine hundred sixty-seven cases of invasive CRC were identified, of which 22.4% were detected in population screening. Of the 1527 cases diagnosed in symptomatic patients, 317 patients had undergone a FIT in the year before the diagnosis of CRC. In 279 cases(18.3%), the result had been positive and this was the first step towards their CRC diagnosis (group 1). Group 2 was composed of the 1248 cases of CRC (81.7%). Considering these cases, 1210 patients with CRC did not undergo any FIT while 38 patients presented a negative result in the year before the diagnosis. The rate of early-stage disease (stage I or II) was higher in group 1 (51.3% vs 45.5% in group 2) (p = 0.04). Furthermore, the 3-year survival was longer in group 1 (72% vs 59% in group 2) (HR 1.50; 95% CI 1.22-1.84).The variables independently associated with worse survival were: group 2, age > 70 years and stage at the moment of diagnosis. CONCLUSIONS: The use of FIT as a diagnostic strategy in symptomatic patients may improve survival in CRC. Nonetheless,FIT is still not widely used in our region.