Is it true that chronic sinusitis flare up would cause only minor increase in the WBC of a cbc?

Yes. Chronic sinusits is just that, chronic. One could have this condition and not have a response of raising the white blood cell count. The body is handling the infections on a chronic basis and does not respond by sending out the numbers of white cells to raise the total circulating count.
Yes. Chronic sinusitis may cause little or no change in the WBC count. A CBC is of no value in diagnosing chronic sinusitis.

Related Questions

Husband gets freq colds [7-10 times in past 3 mo]. Has chronic sinusitis, live in CA, have a preschooler, CBC normal. ESR:39. Shd we worry abt cancer?

Doubt cancer, but... With such frequent recurrent symptoms, I would be more suspicious of an allergy problem rather than repeated upper respiratory infections; or a combination, with minor colds triggering allergic symptoms. Cancer is not a likely explanation for any of this. Howver, an ESR of 39 definitely needs evaluation for an underlying health problem; maybe just persisting sinusitis, but better safe than sorry. Read more...