Introduction:
Chromogranin A belongs to the acidic, soluble protein present in the secretory vesicles of neuroendocrine.
Immunohistochemical studies have demonstrated that chromogranin A is present in virtually all granulecontaining
endocrine cells and in the great majority of tumors of neuroendocrine origin.

Biochemistry:
Molecular weight: 49 kD, 431 amino acid (32% glutamic acid) encoded on chromosome 14
Isoelectric point (PI): 4.75 – 4.68
Half-life: 18 minutes in circulation

Clinical Applications:

1. A very sensitive (83%) and highly specific (96%) diagnostic marker in the evaluation of actual or suspected pheochromocytoma. Drugs commonly employed in the diagnosis or treatment of pheochromocytoma has little effect on the plasma chromogranin A level.
2. To ascertain the source of a tumor. A high chromogranin A level indicates that the tumor arises from neuroendocrine tissues.
3. Endocrine tumors that do not produce their specific hormones, for example, calcitonin negative but chromogranin A positive C-cell carcinoma; zero-cell carcinoma; beta-cell carcinoma; parathyroid carcinoma.

Assay format: “sandwich” immunoenzymometric assay using a monoclonal and a polyclonal human chromogranin A specific antibodies
Patient sample: serum or plasma
Sample pretreatment: none
Sample volume required: 0.05 mL
Normal range: < 100 ng/mL
Assay incubations: < 4 hours

No high dose “Hook” effect up to 1,000,000 ng/mL

References:

1. Pirker RA, Pont J, Pöhnl R, Schütz W, Griesmacher A, Müller MM. Usefulness of chromogranin A as a marker for detection of relapses of carcinoid tumours. Clin Chem Lab Med 1998;36:837-40.
2. Kimura N, Miura W, Noshiro T, Mizunashi K, Hanew K, Shimizu K, et al. Plasma chromogranin A in pheochromocytoma, primary hyperparathyroidism and pituitary adenoma in comparison with catecholamine, parathyroid hormone and pituitary hormones. Endocr J 1997;44:319-27.
3. Hendy GN, Bevan S, Mattei MG, Mouland AJ. Chromogranin A. Clin Invest Med 1995;18:47-65.
4. Deftos LJ. Chromogranin A: its role in endocrine function and as an endocrine and neuroendocrine tumor marker. Endocrine Reviews: 1991;12:181-7
5. Sobol RE, Memoli V, Deftos LJ. Hormone-negative, chromogranin A-positive endocrine tumors. N Engl J Med 1989;320:444-7