title: Mid-regional pro-atrial natriuretic peptide and the assessment of volaemic status and differential diagnosis of profound hyponatraemia.
abstract: BACKGROUND
  Hyponatraemia is common and its differential diagnosis and consequent therapy management is challenging. The differential diagnosis is mainly based on the routine clinical assessment of volume status, which is often misleading. Mid-regional pro-atrial natriuretic peptide (MR-proANP) is associated with extracellular and cardiac fluid volume.
  
  
  METHODS
  A total of 227 consecutive patients admitted to the emergency department with profound hypo-osmolar hyponatraemia (Na < 125 mmol L(-1) ) were included in this prospective multicentre observational study conducted in two tertiary centres in Switzerland. A standardized diagnostic evaluation of the underlying cause of hyponatraemia was performed, and an expert panel carefully evaluated volaemic status using clinical criteria. MR-proANP levels were compared between patients with hyponatraemia of different aetiologies and for assessment of volume status.
  
  
  RESULTS
  MR-proANP levels were higher in patients with hypervolaemic hyponatraemia compared to patients with hypovolaemic or euvolaemic hyponatraemia (P = 0.0002). The area under the curve (AUC) to predict an excess of extracellular fluid volume, compared to euvolaemia, was 0.73 [95% confidence interval (CI) 0.62-0.84]. Additionally, in multivariate analysis, MR-proANP remained an independent predictor of excess extracellular fluid volume after adjustment for congestive heart failure (P = 0.012). MR-proANP predicted the syndrome of inappropriate antidiuresis (SIAD) versus hypovolaemic and hypervolaemic hyponatraemia with an AUC of 0.77 (95% CI 0.69-0.84).
  
  
  CONCLUSIONS
  MR-proANP is associated with extracellular fluid volume in patients with hyponatraemia and remains an independent predictor of hypervolaemia after adjustment for congestive heart failure. MR-proANP may be a marker for discrimination between the SIAD and hypovolaemic or hypervolaemic hyponatraemia.
authors.affiliation: Department of Endocrinology, Diabetology and Metabolism, University Hospital Basel, Basel, Switzerland.|Department of Clinical Research, University Hospital Basel, Basel, Switzerland.
authors.forename: N
authors.initials: N
authors.lastname: Nigro
authors.affiliation: Department of Endocrinology, Diabetology and Metabolism, University Hospital Basel, Basel, Switzerland.|Department of Clinical Research, University Hospital Basel, Basel, Switzerland.
authors.forename: B
authors.initials: B
authors.lastname: Winzeler
authors.affiliation: Department of Endocrinology, Diabetology and Metabolism, University Hospital Basel, Basel, Switzerland.|Department of Clinical Research, University Hospital Basel, Basel, Switzerland.
authors.forename: I
authors.initials: I
authors.lastname: Suter-Widmer
authors.affiliation: Department of Clinical Research, University Hospital Basel, Basel, Switzerland.|Medical University Clinic and Division of Endocrinology, Diabetology and Metabolism, Kantonsspital Aarau, Aarau, Switzerland.
authors.forename: P
authors.initials: P
authors.lastname: Schuetz
authors.affiliation: Department of Endocrinology, Diabetology and Metabolism, University Hospital Basel, Basel, Switzerland.|Department of Clinical Research, University Hospital Basel, Basel, Switzerland.
authors.forename: B
authors.initials: B
authors.lastname: Arici
authors.affiliation: Department of Clinical Research, University Hospital Basel, Basel, Switzerland.|Medical University Clinic and Division of Endocrinology, Diabetology and Metabolism, Kantonsspital Aarau, Aarau, Switzerland.
authors.forename: M
authors.initials: M
authors.lastname: Bally
authors.affiliation: Department of Clinical Research, University Hospital Basel, Basel, Switzerland.|Medical University Clinic and Division of Endocrinology, Diabetology and Metabolism, Kantonsspital Aarau, Aarau, Switzerland.
authors.forename: C A
authors.initials: CA
authors.lastname: Blum
authors.affiliation: Department of Clinical Research, University Hospital Basel, Basel, Switzerland.|Department of Emergency Medicine, University Hospital Basel, Basel, Switzerland.
authors.forename: C H
authors.initials: CH
authors.lastname: Nickel
authors.affiliation: Department of Clinical Research, University Hospital Basel, Basel, Switzerland.|Department of Emergency Medicine, University Hospital Basel, Basel, Switzerland.
authors.forename: R
authors.initials: R
authors.lastname: Bingisser
authors.affiliation: Department of Clinical Research, University Hospital Basel, Basel, Switzerland.|Division of Nephrology, Dialysis and Transplantation, Kantonsspital Aarau, Aarau, Switzerland.
authors.forename: A
authors.initials: A
authors.lastname: Bock
authors.affiliation: Department of Clinical Research, University Hospital Basel, Basel, Switzerland.|Institute of Laboratory Medicine, University Hospital Basel, Basel, Switzerland.
authors.forename: K
authors.initials: K
authors.lastname: Rentsch Savoca
authors.affiliation: Department of Clinical Research, University Hospital Basel, Basel, Switzerland.|Institute of Laboratory Medicine, Kantonsspital Aarau, Aarau, Switzerland.
authors.forename: A
authors.initials: A
authors.lastname: Huber
authors.affiliation: Department of Clinical Research, University Hospital Basel, Basel, Switzerland.|Medical University Clinic and Division of Endocrinology, Diabetology and Metabolism, Kantonsspital Aarau, Aarau, Switzerland.
authors.forename: B
authors.initials: B
authors.lastname: Müller
authors.affiliation: Department of Endocrinology, Diabetology and Metabolism, University Hospital Basel, Basel, Switzerland.|Department of Clinical Research, University Hospital Basel, Basel, Switzerland.
authors.forename: M
authors.initials: M
authors.lastname: Christ-Crain
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D009320:Atrial Natriuretic Factor / Q000097:blood*; D015415:Biomarkers / Q000097:blood; D001810:Blood Volume; D003937:Diagnosis, Differential; D045604:Extracellular Fluid / Q000378:metabolism*; D005260:Female; D006333:Heart Failure / Q000097:blood / Q000150:complications; D006801:Humans; D007010:Hyponatremia / Q000175:diagnosis* / Q000209:etiology / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D020097:Natriuretic Peptide, Brain / Q000097:blood; D011446:Prospective Studies
chemical_list: D015415:Biomarkers; D020097:Natriuretic Peptide, Brain; D009320:Atrial Natriuretic Factor
keywords: mid-regional pro-atrial natriuretic peptide; profound hyponatraemia; volume status