title: Progastrin-releasing peptide: stability in plasma/serum and upper reference limit.
abstract: BACKGROUND
  Progastrin-releasing peptide (proGRP) is a promising tumor marker for small cell lung cancer (SCLC). Here we study the stability of proGRP in serum and plasma, as well as proGRP levels in healthy individuals, to provide a framework for clinical studies.
  
  
  METHODS
  Serum, with and without protease inhibitors, and plasma from SCLC patients and healthy individuals were assayed for proGRP immediately after collection and following various storage conditions.
  
  
  RESULTS
  No degradation was observed in serum or plasma after storage for 4 weeks at -30 degrees C. Serum proGRP levels were stable for up to 3 days at 4 degrees C, but decreased at room temperature. Addition of protease inhibitors to patient serum did not markedly improve stability. In EDTA plasma, proGRP concentrations increased upon storage in some samples at room temperature and 4 degrees C. When assayed immediately after collection, no significant variations in proGRP concentrations were observed between serum and EDTA plasma (n = 171). A 97.5-percentile reference limit of 58.9 ng/l was calculated from data from 806 individuals. However, proGRP levels were significantly correlated with age, sex, creatinine concentrations, body mass index and smoking.
  
  
  CONCLUSIONS
  Serum is the preferred material for measuring proGRP, provided it is stored at 4 degrees C and assayed within 3 days.
authors.affiliation: Department of Medical Biochemistry at Radiumhospitalet, Rikshospitalet Medical Centre, Oslo, Norway.
authors.forename: Marianne S
authors.initials: MS
authors.lastname: Nordlund
authors.forename: Johan
authors.initials: J
authors.lastname: Bjerner
authors.forename: David J
authors.initials: DJ
authors.lastname: Warren
authors.forename: Kjell
authors.initials: K
authors.lastname: Nustad
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Paus
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000097:blood; D014408:Biomarkers, Tumor / Q000097:blood; D001800:Blood Specimen Collection / Q000379:methods*; D015992:Body Mass Index; D018288:Carcinoma, Small Cell / Q000097:blood*; D016022:Case-Control Studies; D003404:Creatinine / Q000097:blood; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000097:blood*; D008297:Male; D008875:Middle Aged; D010446:Peptide Fragments / Q000032:analysis / Q000097:blood*; D010949:Plasma / Q000737:chemistry; D011480:Protease Inhibitors; D011994:Recombinant Proteins / Q000032:analysis / Q000097:blood; D012016:Reference Values; D012907:Smoking / Q000097:blood; D013696:Temperature; D013997:Time Factors
chemical_list: D014408:Biomarkers, Tumor; D010446:Peptide Fragments; D011480:Protease Inhibitors; D011994:Recombinant Proteins; C087079:pro-gastrin-releasing peptide (31-98); D003404:Creatinine