Introduction Survival from colorectal carcinoma (CRC) has not recently improved in the UK despite various initiatives including rapid investigation clinics and the national screening programme. It can be a difficult disease to diagnose. A new diagnostic device (Colonix®) that obtains an imprint of the rectal mucosa has been developed. Early laboratory and pilot studies suggest that the amount of colonocyte DNA correlates well with colorectal pathology. The aim of this study was to assess the diagnostic accuracy of the Colonix® device in identifying CRC in patients with moderate to high risk of colorectal cancer.
Methods Patients were referred by their primary care physicians for further investigation according to the NICE guidelines. Participants completed a symptom questionnaire, had routine blood tests, faecal occult blood test (FOBT) and had a Colonix® test in clinic. The main outcome of the study was the presence of CRC. This was determined histologically by conventional investigation. The quantity of DNA in the sample was measured by investigators blinded to the outcome.
Results 828 patients entered the study: 717 received a Colonix® test. Three were lost to follow-up, leaving 714 patients for analysis of whom 72 (10.1%) had a CRC. The mean (SD) age of those with cancer was 74 years (9.7), and those without 70 (12.4) years. 42 (58%) of the cancers were in males whereas 277 (43%) of those without cancer were male. The mean (SD) DNA score in cancer cases was 7.5 (7.3) ng/ml, and in those without cancer 4.4 (5.6) ng/ml, a significant difference (p<0.001). In univariable logistic regression the odds-ratio of each ng/ml of the DNA score was 1.07 (95% CI 1.04 to 1.11). Using the DNA score alone, the area under the ROC curve was 0.65. The area under the ROC curve improved to 0.87 in multivariable analysis using DNA score, age, mean cell volume (MCV), carcino-embryonic antigen (CEA), positive faecal occult blood test and rectal bleeding.
Conclusion Colonocyte DNA scores obtained using a Colonix® test, have considerable ability to identify colorectal cancer in the referred population when combined with the results of other simple investigations.
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