Any theories on why CRP/ESR test completely normal when in fact significant flare

Mine are always completely normal too even when I had more serious flare ups. I don't even look at ESR/CRP anymore. Hemoglobin is good to check on though for anemia.

Just tell your docs to order the fecal calproctecin stool test, which is a very accurate measure of intestinal inflammation. It's way more accurate to check on your progress overall.

In general CRP and ESR rise with increasing disease activity.

But in some people, they jump WAY up with just a little disease activity.

On the other hand, some people's CRP and ESR never rise, no matter how bad their disease activity is.

The reason for this is not known. I heard one researcher speculate that some people may be genetically incapable of producing CRP, but that was kind of just a guess.

In any case, yes, there are many people for whom CRP and ESR are not good indicators of disease status.

That's why it's always important to consider the whole picture, not just blood tests but symptoms, scope results, etc.

My GI told me once that some people's inflammatory markers don't rise during a flare-up; thus bloodwork is no good for those people in assessing disease activity.

My CRP/ESR rises, but I'm not sure how accurate they are, as I've got no old results to look back on - at my previous hospitals my docs never gave me my blood test results. Obviously nowadays I would just ask for them, but back then I didn't have either the confidence or know-how. Anyway, over the last year my faecal calprotectin has been way higher than either my CRP or ESR. The latter two have been elevated as well - just not as much compared to my FC, and not nearly as much as compared to the days when I was getting admitted to hopsital with toxic megacolon and stuff.

Mia's also right about platelets and white blood cells. White blood cells are more general, but I think increased platelets are specific to IBD - or at least more specific than white blood cells. At any rate, my platelets are measured and they are usually elevated.