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Evaluation of copeptin and commonly used laboratory parameters for the differential diagnosis of profound hyponatraemia in hospitalized patients: ‘The Co‐ MED Study'
Author(s) -
Nigro Nicole,
Winzeler Bettina,
SuterWidmer Isabelle,
Schuetz Philipp,
Arici Birsen,
Bally Martina,
Blum Claudine A.,
Nickel Christian H.,
Bingisser Roland,
Bock Andreas,
Huber Andreas,
Müller Beat,
ChristCrain Mirjam
Publication year - 2017
Publication title -
clinical endocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.055
H-Index - 147
eISSN - 1365-2265
pISSN - 0300-0664
DOI - 10.1111/cen.13243
Subject(s) - copeptin , medicine , hyponatremia , differential diagnosis , endocrinology , vasopressin , gastroenterology , urinalysis , urinary system , pathology
Summary Objective Hyponatraemia is common and its differential diagnosis is challenging. Commonly used diagnostic algorithms have limited diagnostic accuracy. Copeptin, the c‐terminal portion of the precursor peptide of arginine vasopressin might help in the differential diagnosis of hyponatraemia. Design Prospective multicentre observational study. Patients/Methods A total of 298 patients admitted with profound hypoosmolar hyponatraemia (Na < 125 mmol/l) were evaluated. Three experts uninvolved in the patients' care determined the aetiology of hyponatraemia after standardized diagnostic evaluation. Results Hyponatraemia differential diagnoses were as follows: syndrome of inappropriate antidiuresis ( SIAD ), 106 patients (35·6%); ‘diuretic‐induced’, 72 (24·2%); ‘hypovolaemic’, 59 (19·8%); ‘hypervolaemic’, 33 (11·1%); primary polydipsia ( PP ), 24 (8·1%); and cortisol deficiency, 4 (1·3%). Copeptin levels <3·9 pmol/l identified patients with PP with high specificity (91%). Further, copeptin levels >84 pmol/l were highly predictive for hypovolaemic hyponatraemia (specificity: 90%). Urinary sodium levels and copeptin/urinary sodium ratio in patients with SIAD were higher and lower as compared to other hyponatraemia aetiologies ( P < 0·0001). However, the specificity to identify SIAD was moderate for both parameters (31% and 61%). Fractional uric acid excretion ( FE UA ) and fractional urea excretion ( FE urea ) were higher in patients with SIAD compared to other hyponatraemia aetiologies (both P < 0·0001). FE urea values >55% and FE UA values >12% had a specificity of 96% and 77% to detect patients with SIAD . These results remained similar after excluding patients taking diuretics. Conclusions Overall, there is only limited diagnostic utility of copeptin in the differential diagnosis of profound hyponatraemia. Very low copeptin levels are seen in patients with PP and highest copeptin levels in hypovolaemic hyponatraemia. To discriminate between SIAD and other hyponatraemia aetiologies, FE urea and FE UA levels are valuable irrespective of diuretics use.