C Difficile Diagnosis-false negative?

I am a 44 year old female in generally good health until recently.  Several weeks ago I had strep throat and was given Erythromycin for it.  Six days into the treatment, I developed stomach cramps and diarrhea (8-12 bowel movements per day) and discontinued the Erythromycin.  After two more days of diarrhea, I went to the ER, and they tested me for C. Difficile.  I tested negative. My blood tests showed I had an inflammation somewhere in my body.  This was five days ago, and I continue to have the same symptoms of diarrhea-it is watery, but does not have any distinct odor.  My family doctor is going to test me for C. Difficile again, but cannot until I finish menstruating.  He is also doing many other stool tests.

My question is, was the first negative result reliable, given that I am still experiencing symptoms?  I am on a BRAT diet, at my GP's request.  My B.M.s are slightly firmer, but still diarrheal.  My family doc also said it was okay to take Imodium (immodium) for my symptoms, so I am using it as needed.  The minute I try to go off the BRAT diet, I experience diarrhea again.  So, was the first test result (negative) reliable?

[Kevin Pho, MD]

Yes, there is always the possibility of a false negative with C difficile tests.  If there continues to be suspicion, repeating the test, or empirically starting treatment can be considered.

There are other causes that can lead to chronic diarrhea, including other bacterial or parasite infections, inflammatory bowel disease or irritable bowel syndrome.  

Obtaining stool cultures to look for other sources of infection can be considered, and a colonoscopy performed if the symptoms continue.

This answer is not intended as and does not substitute for medical advice - the information presented is for patient education only. Please see your personal physician for further evaluation of your individual case.

Kevin Pho, M.D.

KevinMD.com
Twitter.com/kevinmd