Accurate if you have cancer that is so bad it is bleeding. About the only cancer the poop sample test shows, is metastasized. The thing about the scope is it also has a tool for removing polyps so they can be biopsied. Also the colon can be examined for other disease.
Endoscopy and Colonoscopy have saved many lives. Recently a long time friend died because he wouldn't get a colonoscopy until his poop test showed cancer. The scope confirmed a large cancer and surgery removed it with half his colon. It biopsied stage 4 and scans showed the cancer had spread. He went to Mexico to their famous holistic cancer clinic. He got worse and then decided on chemotherapy. He lived about 9 months and it wasn't a pleasant existence.
Men seem to be the worst about getting a colonoscopy. I think they see it as an assault on their being a male, perhaps an insult on their masculinity. Some men had rather die a horrible death than get a life saving colon invasion. The thing about being female is invasive procedures are just a way of life.
Males have no problem invading the female body, but suggest the male undergo a possibility life saving invasion that they will not even remember, and they run, hide, and poop in a box. Very few can change a ripe baby diaper, but they can take a popsicle stick and smear fecal matter

into a container some poor lab worker has to test.

I suppose it is a, me Tarzan, you Jane thing.