If you are Type O and your doctor does the standard screen for blood in your stool, you have a HIGH probability of a false positive. Your doctor may not know to tell you this, and the consequences can be very painful and expensive.

I went to my family doctor yesterday for a follow up after the disastrous colonoscopy. The specialist (who I hope to never set eyes on again) wants to more tests (expensive of course) since he didn't find anything that would explain the blood that showed up in my original stool test. I told my doctor that I refused to have any more tests unless there was a medical reason for them. We compromised that I would do 3 consecutive days of stool smears at home. If no blood showed up he would close the issue, if blood showed up, I would do the tests.

This morning I read the instructions for the standard stool smear test. It said, "DO NOT EAT red meat, turnips, broccoli, horseradish, cantaloupe, parsnips, radishes or cauliflower" for two days before taking the sample.

What is this?!? I eat red meat and broccoli daily. I eat turnips and parsnips multiple times each week. I had probably eaten three or more of those items before my original test.

I called the test manufacturer, and talked with a very knowledgeable man. He said it was extremely important to follow the instructions or I would get a false positive. He said that even fish and chicken can cause a false positive if they are not thoroughly cooked. He said that doctors use this test because it is easy to do and inexpensive. There is a more advanced test available that is specific for human blood, but the kit is more complicated and more expensive.

He offered to send my doctor a free sample of the newer kit to test me. I have faxed the doctor this information.

Here is what you need to know. If you are eating a Type O diet you are likely to get a false positive on the stool smear they do in a routine physical. You can lessen your chances by not eating red meat or the vegetables on the testing company's list for two days before the test. If you get a positive test result, before submitting to the next round of expensive, invasive tests insist on another stool smear that is human blood specific.