title: N-terminal-pro-brain natriuretic peptide for the differential diagnosis of hypovolemia vs. euvolemia in hyponatremic patients.
abstract: BACKGROUND
  Hyponatremia (serum sodium < 135 mEq/L) is the most common electrolyte abnormality in hospital and has impact on patient morbidity and mortality. The accuracy of volume status assessment is a major problem for the treatment planning especially to discriminate mild hypovolemic from euvolemic patients.
  
  
  OBJECTIVE
  To examine the relationship between plasma N-Terminal-pro-Brain Natriuretic Peptide (NT-pro-BNP) level and extracellular water (ECW) status during the treatment of hyponatremia, as well as the cut-off value of plasma NT-pro-BNP in the differential diagnosis of volume status in hypovolemic vs. euvolemic hyponatremic patients.
  
  
  METHODS
  Hyponatremic patients without clinical hypervolemia in Rajavithi Hospital were divided into the hypovolemic group and the euvolemic group according to ECW volume determined by bioimpedance analysis (BIA). Serum sodium, plasma NT-pro-BNP and ECW were assessed at the beginning, at the half correction of hyponatremia and at the end of treatment.
  
  
  RESULTS
  Of the 26 patients, 18 (69.2%) were hypovolemic and 8 (30.8%) were euvolemic. Before treatment, NT-pro-BNP levels of the patients with hypovolemia was significantly lower than the patients with euvolemia [median (min, max)] (pg/mL) of hypovolemic vs. euvolemic group [114 (21, 6,803) vs. 1,509 (538, 8,541)] respectively (p < 0.001) and NT-pro-BNP levels change in the similar direction as ECW volume during the treatment. The best cut-off value of plasma NT-pro-BNP level to distinguish hypovolemic from euvolemic hyponatremia was 518 pg/ml with the sensitivity of 94.4% and the specificity of 100%.
  
  
  CONCLUSIONS
  Plasma NT-pro-BNP levels provide objective information with respection to volume status in hyponatremia patients and can be used in clinical diagnosis of hypovolemic vs. euvolemic hyponatremic hyponatremia.
authors.affiliation: Department of Medicine, Rajavithi Hospital, College of Medicine, Rangsit University, Bangkok, Thailand. Sakarnbunnag@yahoo.com
authors.forename: Sakarn
authors.initials: S
authors.lastname: Bunnag
authors.forename: Kampol
authors.initials: K
authors.lastname: Pattanasombatsakul
mesh_terms: D000328:Adult; D000368:Aged; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007010:Hyponatremia / Q000150:complications*; D020896:Hypovolemia / Q000175:diagnosis* / Q000209:etiology; D008297:Male; D008875:Middle Aged; D020097:Natriuretic Peptide, Brain / Q000032:analysis*; D010446:Peptide Fragments / Q000032:analysis*; D012372:ROC Curve
chemical_list: D010446:Peptide Fragments; C109794:pro-brain natriuretic peptide (1-76); D020097:Natriuretic Peptide, Brain