Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (816 page)

   Anabolic steroids, carbamates, cyclophosphamide, estrogens, glucocorticoids, lithium, neuromuscular relaxants, oral contraceptives, organophosphorus insecticides, and radiographic agents decrease the circulating levels.

   Serum separator tubes, citrate anticoagulants, detergents, and heavy metals also decrease the serum levels.

CHORIONIC VILLUS SAMPLING

See Prenatal Screening.

CHROMOGRANIN A, PLASMA

   Definition

   Chromogranin, also known as CGA and parathyroid secretory protein 1, is a member of the chromogranin/secretogranin (granins) family of neuroendocrine secretory proteins. It is a precursor to several functional peptides, including vasostatin, pancreastatin, catestatin, and parastatin. These peptides negatively modulate the neuroendocrine function of the releasing cell (autocrine) or nearby cells (paracrine). Chromogranin A is cleaved by an endogenous prohormone convertase to produce several peptide fragments. Peptides derived from chromogranin A with uncertain function include chromostatin, WE-14, and GE-25. The method of measurement is EIA.

   
Normal range:
0–50 ng/mL.

   Use

   As an indicator for pancreas and prostate cancer

   Aid in diagnosis of functioning neuroendocrine tumors; predicts response to treatment

   Aid in diagnosis of nonfunctioning neuroendocrine tumors (e.g., thyroid carcinoma, small cell lung cancer, anterior pituitary adenoma)

   Interpretation

Disorders with Increased Values

   Functioning neuroendocrine tumors and hyperplasia

   Pheochromocytoma, aortic, and carotid body tumors

   Neural tumors (e.g., neuroblastoma, ganglioneuroma, paraganglioma, medulloblastoma)