Background Screening tests for precancerous polyps and early CRC reduce mortality. Cologuard is a stool-based, commercially available, molecular screening tool that detects occult blood in combination with multiple DNA abnormalities released from neoplastic colonic cells (from small polyps to cancers). Previous population-based studies reported a sensitivity and specificity of 69%–92% and 87% respectively for detection of polyps.
Aim To evaluate the Cologuard in asymptomatic low risk surveillance and symptomatic patients.
Method Ethics approval was obtained and patients were recruited from endoscopy referrals and the colonoscopy surveillance waiting list. Inclusion and exclusion criteria in Table 1. Participants provided stool for Cologuard prior to colonoscopy. Cologuard and Colonoscopy results were correlated to calculate NPV, PPV, sensitivity and specificity.
Results 60 patients were recruited. To date 40 have completed the study. 22 (55%) female. Median age 60 years (range 42–80). 18 (45%) patients were symptomatic. Colonoscopy adenoma detection rate was 28% (n=11). Cologuard was positive in 10 (25%) patients, 4 of whom had adenomatous polyps, 1>10 mm size and 3<5 mm. Of 7 negative Cologuard patients with adenomatous polyps 1>1 cm in size, 1=7 mm and 5<5 mm. Cologuard was negative in 23/29 (79%) with normal Colonoscopy. The NPV and PPV of Cologuard were 77%–40%, with 36% sensitivity, and 79% specificity. NPV is 90% for polyps>5 mm. No CRC was diagnosed.
Conclusions Cologuard seems reliable for excluding CRC and adenomatous polyps>5 mm in size, and maybe useful in triaging surveillance patients for Colonoscopy.