title: Validation of serum versus plasma measurements of chromogranin a levels in patients with carcinoid tumors: lack of correlation between absolute chromogranin a levels and symptom frequency.
abstract: OBJECTIVE
  Chromogranin A (CGA) levels are used to confirm the diagnosis and monitor the course of patients with neuroendocrine tumors. Chromogranin A levels are significantly reduced when patients are acutely treated with octreotide; however, limited data are available that correlates octreotide long-acting repeatable (LAR) dose or steady state octreotide blood levels to the absolute value of serum or plasma CGA.
  
  
  METHODS
  Plasma, serum, and clinical information on carcinoid syndrome symptoms were collected anonymously from 40 patients treated with long-term octreotide LAR therapy for carcinoid syndrome.
  
  
  RESULTS
  We found a strong positive linear relationship exists between serum and plasma CGA levels (r = 0.9858, P < 0.0001). No correlation existed between plasma octreotide levels or LAR dose and the static, absolute plasma/serum CGA levels. Although, higher mean CGA values were seen in the group whose diarrhea was "not under optimal control" than for the group "under optimal control," these results did not reach statistical significance (P = 0.24). Contrary to our hypotheses, a statistically significant inverse relationship was found between the frequency of flushing and the CGA levels (P = 0.0372). Higher mean CGA values were observed in the "under optimal control" group with flushing symptoms.
  
  
  CONCLUSIONS
  Either serum or plasma can be used to measure CGA levels. Absolute (static) CGA levels do not positively correlate with symptom intensity during LAR therapy. Dynamic (serial) measurements of CGA are necessary to monitor the effectiveness of medical or surgical therapy.
authors.affiliation: Section of Surgical Endocrinology, Department of Surgery, Louisiana State University Health Sciences Center, New Orleans, LA, USA. ewolte@lsuhsc.edu
authors.forename: Eugene A
authors.initials: EA
authors.lastname: Woltering
authors.forename: Ruth S
authors.initials: RS
authors.lastname: Hilton
authors.forename: Christy M
authors.initials: CM
authors.lastname: Zolfoghary
authors.forename: Jessica
authors.initials: J
authors.lastname: Thomson
authors.forename: Stanley
authors.initials: S
authors.lastname: Zietz
authors.forename: Vay Liang W
authors.initials: VL
authors.lastname: Go
authors.forename: Aaron I
authors.initials: AI
authors.lastname: Vinik
authors.forename: Etta
authors.initials: E
authors.lastname: Vinik
authors.forename: Thomas M
authors.initials: TM
authors.lastname: O'Dorisio
authors.forename: Gregg
authors.initials: G
authors.lastname: Mamikunian
mesh_terms: D018931:Antineoplastic Agents, Hormonal / Q000627:therapeutic use; D002276:Carcinoid Tumor / Q000097:blood* / Q000175:diagnosis* / Q000188:drug therapy; D053379:Chromogranin A; D002864:Chromogranins / Q000097:blood*; D006801:Humans; D015282:Octreotide / Q000627:therapeutic use; D010190:Pancreatic Neoplasms / Q000097:blood* / Q000175:diagnosis* / Q000188:drug therapy; D010949:Plasma; D012044:Regression Analysis; D015203:Reproducibility of Results; D044967:Serum
chemical_list: D018931:Antineoplastic Agents, Hormonal; C506150:CHGA protein, human; D053379:Chromogranin A; D002864:Chromogranins; D015282:Octreotide