Original Title: Équivalence du seuil de positivité des tests immunochimiques de recherche de sang occulte dans les selles pour le dépistage du cancer colorectal

Authors' objectives: Colorectal cancer (CRC) screening with the OC-SensorTM immunochemical fecal occult blood (iFOB) test has been available in Quebec since 2013. The expiry of this contract, and the availability of new Health Canada-approved iFOB tests compatible with Quebec’s needs, have prompted the Ministère de la Santé et des Services sociaux (MSSS) to issue a call for bids. If the test were to be changed, the Direction générale de la santé publique (DGSP) and the Direction générale des affaires universitaires, médicales, infirmières et pharmaceutiques (DGAUMIP) would like to know the equivalent positivity threshold that would give the same performance as the OC-SensorTM test, at 35 μg hemoglobin/g feces (175 ng Hb/ml buffer), in terms of the balance between sensitivity for significant colorectal lesions and the number of cases referred for diagnostic colonoscopy, for the new test to be chosen.

Authors' results and conclusions: RESULTS (#1 SOCIOCULTURAL DIMENSION): Many countries have implemented colorectal cancer screening programs. The iFOB test is the most widely used screening method in these programs. These quantitative tests, often fully automated, have the advantage of adjusting their positivity threshold according to several parameters specific to different authorities, including disease incidence, participation rates and diagnostic colonoscopy capacity. In Quebec, CRC screening with the OC-SensorTM test at a threshold of 35 μg/g has been performed opportunistically for the past 10 years. It targets adults aged 50 to 74 with an average risk of developing CRC. (#2 POPULATION DIMENSION): Colorectal cancer is the third most common cancer in Canada, and the second leading cause of cancer-related death. In 93% of cases, the patient is an adult aged 50 or over. CRC can progress over a period of 5 to 15 years. In its early stages, CRC is often asymptomatic, so by the time it is diagnosed, it is already at an advanced stage, and the prognosis is often poor. The stage of CRC at diagnosis is therefore the most important predictor of survival. With screening, almost half of all CRCs are diagnosed early, which means a better prognosis.(#3 CLINICAL DIMENSION): Three iFOB tests, OC-Sensor, FOB-Gold and NS-PRIME approved by Health Canada, and which meet the needs of CRC screening managers in Quebec, have been described in this state of knowledge. Their diagnostic performance at different thresholds was extracted from 13 scientific publications, published between 2012 and 2023. No data on the performance of CRC screening in Quebec with the OC-SensorTM test at a positivity threshold of 35 μg/g have been published in the scientific literature. In all the clinical studies selected, the diagnostic performance of the three tests was evaluated in populations from various countries where CRC prevalence may vary, each with screening targets adapted to its own requirements and capabilities. Due to significant heterogeneity in test performance, despite an equivalent positivity threshold, and the absence of Quebec data, it was not possible to determine the equivalent threshold, for other tests, which would theoretically enable performance similar to the OC-SensorTM test at the 35 μg/g threshold. However, the experience in other countries, such as the Netherlands, which have had to change test during the program, raises a few points for consideration. In particular, within the same population, tests would be equivalent in terms of performance if the threshold value used is set to ensure that the same positivity rate is maintained over time.(#4 ORGANIZATIONAL DIMENSION): The choice of a iFOB test and its analysis device involves the evaluation of various factors. Convenience of fecal sample collection can be a crucial factor, as it can affect the feasibility and acceptance of the test by participants. Similarly, the instrument's sampling capacity, the analytical range defining adjustable threshold limits and the ease of performing the analysis in the laboratory are also factors to be considered when choosing a test. Furthermore, the stability of samples under normal environmental conditions is important to ensure reliable results. With this knowledge, the characteristics of the iFOB, OC-Sensor, FOB-Gold and NS-PRIME tests were examined. CONCLUSION: Establishing a threshold equivalence for other iFOB tests without the current screening performance in Quebec with the OC-SensorTM at a threshold of 35 μg/g is difficult to achieve. Based on the positivity rates of clinical studies conducted in other countries, this could lead to variable results, potentially compromising the capabilities of the healthcare system in Quebec, particularly in terms of access to confirmatory colonoscopies. Data on the performance of the OC-SensorTM at a threshold of 35 μg/g in the Quebec population are essential for defining the equivalent positivity threshold (or threshold interval) for other iFOB tests. An analysis of the distribution of threshold positivity rates with the various iFOB tests in the Quebec population undergoing screening is necessary to compare the tests with each other and establish threshold equivalence.

Project Status: Completed

URL for project: https://www.inesss.qc.ca/en/publications/publications/publication/equivalence-du-seuil-de-positivite-des-tests-immunochimiques-de-recherche-de-sang-occulte-dans-les-selles-pour-le-depistage-du-cancer-colorectal.html

Year Published: 2024

URL for published report: https://www.inesss.qc.ca/en/publications/publications/publication/equivalence-du-seuil-de-positivite-des-tests-immunochimiques-de-recherche-de-sang-occulte-dans-les-selles-pour-le-depistage-du-cancer-colorectal.html

English language abstract: An English language summary is available

Publication Type: Other

Country: Canada

Province: Quebec

Organisation Name: Institut national d'excellence en sante et en services sociaux

Contact Address: L'Institut national d'excellence en sante et en services sociaux (INESSS) , 2021, avenue Union, bureau 10.083, Montreal, Quebec, Canada, H3A 2S9;Tel: 1+514-873-2563, Fax: 1+514-873-1369

Contact Name: demande@inesss.qc.ca

Contact Email: demande@inesss.qc.ca

Copyright: L'Institut national d'excellence en sante et en services sociaux (INESSS)