Calprotectin

  1. samples out at room temperature, does the result of Calprotectin assay decrease or increase?

    Calprotectin is stable in stool samples at room temperature for 7 days, according to literature (attached). A longer storage would lead to degradation of calprotectin and thus to lower results.

  2. What should the patients be careful about in stool sampling? If the samples are rich in mucus, I expect the result of Calprotectin assay tends to increase?

    This is one drawback of all calprotectin assays in general, because stool texture is of course important and will influence measured calprotectin levels. For instance very liquid stool might underestimate the calprotectin level, but you can't help it, it is due to the material we work with, an stool is not that standardized as blood. I'm not sure that samples rich in mucus would give higher results, but they may of course differ from samples with normal stool. Because of these limitations calprotectin results should always be interpreted with caution and in the context of stool texture and clinical signs.

  3. In calprotectin assay, do we measure quantity of calprotectin released outside cells in stool - or calprotectin inside and outside the cells in stool?

    Is this important? In stool there are certainly both intact and destroyed cells. Calprotectin occurs in stool because in intestinal inflammation granulocytes migrate through the intestinal wall into the intestinal lumen. There they may stay intact or may be destroyed. During stool extraction it may also happen that cells are destroyed. Thus, I would say that we certainly measure calprotectin level outside the cells, but it is derived from cell destruction, either by physiological processes or by extraction.

  4. Why does the instrument ask for a new calibration curve if I only change the EliA Calprotectin Calibrator Well lot?

    EliA Calprotectin uses the same logic as the other EliA calibration systems (EliA IgG, EliA IgA, EliA IgM...). You are probably used to the fact that you can change the EliA Calibrator Well Lot without having to run new curves in these systems. BUT (also with the other calibration systems) you have to run a new curve if the Calibrator Code changes! For EliA IgG/M/A this is usually not the case as in recent years they always had the code 0000000. Bor the EliA Calprotection Calibrator Wells the lot specific code changes from lot to lot. Therefore you have to run new curves when you change the Calibrator Well lot (because the new lot will most likely have a different cal well code).

As in all diagnostic testing, the diagnosis is made by the physican based on both test results and the patient history.