Assay for determination of the serum procalcitonin level: biochemical and clinical evaluation

In patients with inflammatory conditions such as infection, cytokines induce the production of C-reactive protein(CRP) and serum amyloid A protein(SAA) in hepatic cells. It has been reported that upon viral infection, the serum SAA level increases by a greater degree than the serum CRP level. Procalcitonin (PCT), the precursor of calcitonin, is a new type of inflammatory marker that is specifically induced by bacterial infection, sepsis and lethal multiple organ failure, but not by viral infection, autoimmune diseases, tumors or surgical stress. To evaluate the immunoluminometric assay(LUMI test PCT; Brahms Diagnostics, Berlin, Germany) procedure for determining the PCT level and to study the clinical significance of the serum PCT level, we determined the serum levels of PCT, CRP and SAA in patients with various inflammatory diseases and normal subjects. The serum PCT level in the normal subjects was < 0.3 ng/ml. Among the patients with inflammatory disease who had a high CRP level(CRP > 20000 micrograms/dl), the PCT level was elevated only in those patients with severe bacterial infection. These results suggest that determining the PCT level may be useful in the differential diagnosis of severe bacterial infection. The patients who had a low CRP level(CRP < 150 micrograms/dl), had a PCT level within the normal range. The patients with autoimmune disease, viral infection, and fungal infection did not have an elevated PCT level.