Development of a microplate assay for serum chromogranin A (CgA): establishment of normal reference values and detection of elevated CgA in malignant diseases.

Chromogranin A (CgA), a marker for neuroendocrine cells, is associated with poor prognosis when detected by immunohistochemical technique in prostate tumors. We have developed an ELISA on microplates for serum CgA and established the normal reference range. We also attempted to find out whether elevated serum CgA levels could be found in patients with various malignant diseases. Because of non-Gaussian distribution, both medians and 97.5 percentiles of serum CgA levels for men and women of four different age groups were determined. For women, the median and 97.5 percentiles are 20.7 and 63.9 ng/mL for ages 20 to 50, and 32 and 93.8 for 50 to 80 years of age, respectively; for men, they are 27.9 and 78.4 ng/mL for ages 18 to 40 and 41.6 and 92 for 40 to 80 years old, respectively. Elevated serum concentrations of CgA were detectable in patients with prostate cancer not undergoing hormonal treatment, and in patients with various malignant diseases including nonendocrine carcinomas. Most elevated serum CgA levels were associated with sera containing highly elevated serum tumor markers. Drugs targeting neuroendocrine cells should be administered for cancer patients with elevated serum CgA levels.