# Colon cancer test question (NSFW) **URL:** \ **Category:** In My Humble Opinion\ **Created:** [December 14, 2016, 11:29am UTC](https://boards.straightdope.com/t/colon-cancer-test-question-nsfw/774669 "2016-12-14T11:29:21Z")\ **Posts on this page:** 14\ **Page:** 1
**Author:** ![Quartz](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/quartz/32/267_2.png) [@Quartz](https://boards.straightdope.com/u/Quartz)\ **Post date:** [December 14, 2016, 11:29am UTC](https://boards.straightdope.com/t/colon-cancer-test-question-nsfw/774669/1 "2016-12-14T11:29:21Z")
Why can’t I just use the stuff on the toilet paper? The first official recognition of my 50th birthday was a colon cancer test pack. Whee! I’ve dutifully read the instructions and they seem a little odd to me. Note is made of not having the faeces touch the water. I can understand that - people put fresheners etc in the water which could contaminate the result. But why not just use the faecal matter on the toilet paper I use to wipe my arse? I’ve just asked my doctor this and she couldn’t answer me beyond agreeing that it sounded reasonable. Can Dopers supply the answer? ---
**Author:** ![jonesj2205](https://avatars.discourse-cdn.com/v4/letter/j/ecc23a/32.png) [@jonesj2205](https://boards.straightdope.com/u/jonesj2205)\ **Post date:** [December 14, 2016, 12:53pm UTC](https://boards.straightdope.com/t/colon-cancer-test-question-nsfw/774669/2 "2016-12-14T12:53:47Z")
This could be the most disappointing NSFW. But my assumption would be toilet paper contaminates the sample too with both whatever is in toilet paper and in the air that the toilet paper has been exposed to. ---
**Author:** ![Quartz](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/quartz/32/267_2.png) [@Quartz](https://boards.straightdope.com/u/Quartz)\ **Post date:** [December 14, 2016, 1:24pm UTC](https://boards.straightdope.com/t/colon-cancer-test-question-nsfw/774669/3 "2016-12-14T13:24:21Z")
> [@jonesj2205](#): > > But my assumption would be toilet paper contaminates the sample too with both whatever is in toilet paper and in the air that the toilet paper has been exposed to. One of the things they suggest in the instructions is putting toilet paper in the toilet before you poop, so that can’t be it. ---
**Author:** ![ftg](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ftg/32/2801_2.png) [@ftg](https://boards.straightdope.com/u/ftg)\ **Post date:** [December 14, 2016, 2:06pm UTC](https://boards.straightdope.com/t/colon-cancer-test-question-nsfw/774669/4 "2016-12-14T14:06:58Z")
The most recent version I’ve seen comes with a good size piece of flushable paper to put on top of the toilet water to catch the future sample and prevent it from being contaminated by the water. Doesn’t work at all, of course. Dear CC test makers: It’s flimsy (flushable) paper. Guess how much weight it can hold without sinking? ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [December 14, 2016, 6:05pm UTC](https://boards.straightdope.com/t/colon-cancer-test-question-nsfw/774669/5 "2016-12-14T18:05:41Z")
I recall reading that optimally healthy human feces floats or almost floats. If you’re normally pooping lumps that sink like rocks you’re not getting nearly enough fiber. ---
**Author:** ![nearwildheaven](https://avatars.discourse-cdn.com/v4/letter/n/90db22/32.png) [@nearwildheaven](https://boards.straightdope.com/u/nearwildheaven)\ **Post date:** [December 15, 2016, 2:42am UTC](https://boards.straightdope.com/t/colon-cancer-test-question-nsfw/774669/6 "2016-12-15T02:42:38Z")
Because the paper may contain chemicals that can alter test results. At my old job, I had a co-worker whose baby had persistent diarrhea, and she couldn’t just bring in a dirty diaper either, for the same reason. ---
**Author:** ![Two\_Many\_Cats](https://avatars.discourse-cdn.com/v4/letter/t/8dc957/32.png) [@Two\_Many\_Cats](https://boards.straightdope.com/u/Two_Many_Cats)\ **Post date:** [December 15, 2016, 3:53am UTC](https://boards.straightdope.com/t/colon-cancer-test-question-nsfw/774669/7 "2016-12-15T03:53:25Z")
> [@LSLGuy](#): > > I recall reading that optimally healthy human feces floats or almost floats. If you’re normally pooping lumps that sink like rocks you’re not getting nearly enough fiber. I heard it was the opposite. Too much fatty food means poop that floats. So which is it? ---
**Author:** ![usedtobe](https://avatars.discourse-cdn.com/v4/letter/u/ec9cab/32.png) [@usedtobe](https://boards.straightdope.com/u/usedtobe)\ **Post date:** [December 15, 2016, 8:30am UTC](https://boards.straightdope.com/t/colon-cancer-test-question-nsfw/774669/8 "2016-12-15T08:30:09Z")
Is there a medical supply store near you? What you would optimally use is called a “top hat” (it looks more like a “boater”, actually). It sits inverted between the bowl rim and the seat. You poop into it and extract a sample (or, for most “fun with testing workers”), just seal it in plastic and ship the entire thing. See [McKesson 16-9522 Toilet Hat Specimen Collector w/o Closure - 27 oz. (800 mL) Capacity | Vitality Medical](http://www.vitalitymedical.com/toilet-hat-specimen-collector-by-medi-pak.html) ---
**Author:** ![Quartz](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/quartz/32/267_2.png) [@Quartz](https://boards.straightdope.com/u/Quartz)\ **Post date:** [December 15, 2016, 9:22am UTC](https://boards.straightdope.com/t/colon-cancer-test-question-nsfw/774669/9 "2016-12-15T09:22:35Z")
> [@nearwildheaven](#): > > Because the paper may contain chemicals that can alter test results. But the instructions suggest I layer toilet paper in the bowl. ---
**Author:** ![DSeid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dseid/32/20194_2.png) [@DSeid](https://boards.straightdope.com/u/DSeid)\ **Post date:** [December 15, 2016, 12:46pm UTC](https://boards.straightdope.com/t/colon-cancer-test-question-nsfw/774669/10 "2016-12-15T12:46:15Z")
Assuming this is the Color Guard test I would guess the following as the major reason. The test is looking _both_ for DNA markers and for microscopic amounts of blood. Either one gives a “positive” result which leads to colonoscopy. At your age and assuming that you are of average risk the vast vast majority of “positive” results already will be false positives. A sample that was wiped off with toilet paper is more likely to have scraped the skin some and collected some microscopic amount of blood and likely dramatically increases the false positive rate. The toilet water may have others’ cells and DNA in it. ---
**Author:** ![Quartz](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/quartz/32/267_2.png) [@Quartz](https://boards.straightdope.com/u/Quartz)\ **Post date:** [December 15, 2016, 1:47pm UTC](https://boards.straightdope.com/t/colon-cancer-test-question-nsfw/774669/11 "2016-12-15T13:47:17Z")
> [@DSeid](#): > > A sample that was wiped off with toilet paper is more likely to have scraped the skin some and collected some microscopic amount of blood and likely dramatically increases the false positive rate. Ah, that sounds logical. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [December 15, 2016, 3:17pm UTC](https://boards.straightdope.com/t/colon-cancer-test-question-nsfw/774669/12 "2016-12-15T15:17:53Z")
FTR the test we might be talking about is “Cologuard”. No matter how much spell-check prefers “color guard”. 🙂 Carry on ---
**Author:** ![DSeid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dseid/32/20194_2.png) [@DSeid](https://boards.straightdope.com/u/DSeid)\ **Post date:** [December 15, 2016, 4:07pm UTC](https://boards.straightdope.com/t/colon-cancer-test-question-nsfw/774669/13 "2016-12-15T16:07:25Z")
Yup, let spellcheck fix me and deferred to its wisdom. Thanks. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [December 15, 2016, 11:35pm UTC](https://boards.straightdope.com/t/colon-cancer-test-question-nsfw/774669/14 "2016-12-15T23:35:14Z")
I didn’t say it, but I was also reacting to the other thread with several posters’ variant misspellings. It was even wrong in the thread title. Some words are just not meant to be spelled right. Which can be a real problem if that word is a trade name.