Is the number of neutrophils and monocytes in "normal" blood high enough to make the fecal calprotectin test become positive even in the case of a non-inflammatory source of bleeding (e.g., bleeding from hemorrhoids)?
Yes it most likely would. Of course, it depends on the extent of bleeding. In animal studies, this was the case (we used calprotectin in a model of NSAID-induced small intestinal damage). Of course, in this particular instance, we were looking for NSAID-induced injury, so an increase in calprotectin as a result of bleeding was as valuable to us as an increase in trans-epithelial neutrophil migration.
Here is the reference, and you can download it from my ResearchGate page: Davies NM, Roseth AG, Appleyard CB, McKnight W, Del Soldato P, Calignano A, Cirino G, Wallace JL. NO-naproxen vs. naproxen: ulcerogenic, analgesic and anti-inflammatory effects. Aliment Pharmacol Ther 1997; 11: 69-79.
Calprotectin accounts for about 30% of neutrophils' cytosol, therefore, the presence of blood in the feces should elevate fecal calprotectin levels. However, in case of occult bleeding from a neoproliferative lesion this is not the case. Fecal calprotectin levels are used to evaluate the inflammatory state of intestinal mucosa.
Thank you to both of you. So, if I got you right, hematochezia will always lead to an elevated calprotectin which will be just higher in case of an inflammatory bleeding source as compared with a non-inflammatory bleeding source.
I think your question is very well answered in the following study recently published .
Article The Vampire Study: Significant elevation of faecal calprotec...
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