title: N-terminal pro-B-type natriuretic peptide variability in stable dialysis patients.
abstract: OBJECTIVE
  Monitoring N-terminal pro-B-type natriuretic peptide (NT-proBNP) may be useful for assessing cardiovascular risk in dialysis patients. However, its biologic variation is unknown, hindering the accurate interpretation of serial concentrations. The aims of this prospective cohort study were to estimate the within- and between-person coefficients of variation of NT-proBNP in stable dialysis patients, and derive the critical difference between measurements needed to exclude biologic and analytic variation.
  
  
  METHODS
  Fifty-five prevalent hemodialysis and peritoneal dialysis patients attending two hospitals were assessed weekly for 5 weeks and then monthly for 4 months between October 2010 and April 2012. Assessments were conducted at the same time in the dialysis cycle and entailed NT-proBNP testing, clinical review, electrocardiography, and bioimpedance spectroscopy. Patients were excluded if they became unstable.
  
  
  RESULTS
  This study analyzed 136 weekly and 113 monthly NT-proBNP measurements from 40 and 41 stable patients, respectively. Results showed that 22% had ischemic heart disease; 9% and 87% had left ventricular systolic and diastolic dysfunction, respectively. Respective between- and within-person coefficients of variation were 153% and 27% for weekly measurements, and 148% and 35% for monthly measurements. Within-person variation was unaffected by dialysis modality, hydration status, inflammation, or cardiac comorbidity. NT-proBNP concentrations measured at weekly intervals needed to increase by at least 46% or decrease by 84% to exclude change due to biologic and analytic variation alone with 90% certainty, whereas monthly measurements needed to increase by at least 119% or decrease by 54%.
  
  
  CONCLUSIONS
  The between-person variation of NT-proBNP was large and markedly greater than within-person variation, indicating that NT-proBNP testing might better be applied in the dialysis population using a relative-change strategy. Serial NT-proBNP concentrations need to double or halve to confidently exclude change due to analytic and biologic variation alone.
authors.affiliation: Departments of Nephrology and School of Medicine and Translational Research Institute, University of Queensland, Brisbane, Queensland, Australia; magid.fahim@health.qld.gov.au.
authors.forename: Magid A
authors.initials: MA
authors.lastname: Fahim
authors.affiliation: School of Medical Sciences, University of New South Wales, Sydney, Australia;
authors.forename: Andrew
authors.initials: A
authors.lastname: Hayen
authors.affiliation: School of Public Health, University of Sydney, Sydney, Australia; Department of Clinical Chemistry, Prince of Wales Hospital, South Eastern Area Laboratory Services, Sydney, Australia; and School of Medical Sciences, University of New South Wales, Sydney, Australia;
authors.forename: Andrea R
authors.initials: AR
authors.lastname: Horvath
authors.affiliation: School of Medicine and Chemical Pathology, Pathology Queensland, Princess Alexandra Hospital, Brisbane, Queensland, Australia;
authors.forename: Goce
authors.initials: G
authors.lastname: Dimeski
authors.affiliation: Departments of Nephrology and.
authors.forename: Amanda
authors.initials: A
authors.lastname: Coburn
authors.affiliation: Departments of Nephrology and School of Medicine and Translational Research Institute, University of Queensland, Brisbane, Queensland, Australia;
authors.forename: David W
authors.initials: DW
authors.lastname: Johnson
authors.affiliation: Departments of Nephrology and School of Medicine and Translational Research Institute, University of Queensland, Brisbane, Queensland, Australia;
authors.forename: Carmel M
authors.initials: CM
authors.lastname: Hawley
authors.affiliation: Departments of Nephrology and School of Medicine and.
authors.forename: Scott B
authors.initials: SB
authors.lastname: Campbell
authors.affiliation: School of Public Health, University of Sydney, Sydney, Australia; Centre for Kidney Research, The Children's Hospital at Westmead, Sydney, Australia.
authors.forename: Jonathan C
authors.initials: JC
authors.lastname: Craig
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001315:Australia; D015415:Biomarkers / Q000097:blood; D005260:Female; D006801:Humans; D007674:Kidney Diseases / Q000097:blood* / Q000150:complications / Q000175:diagnosis / Q000628:therapy*; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000097:blood / Q000175:diagnosis / Q000209:etiology; D020097:Natriuretic Peptide, Brain / Q000097:blood*; D010446:Peptide Fragments / Q000097:blood*; D010530:Peritoneal Dialysis / Q000009:adverse effects; D011237:Predictive Value of Tests; D011446:Prospective Studies; D006435:Renal Dialysis / Q000009:adverse effects; D015203:Reproducibility of Results; D012307:Risk Factors; D013997:Time Factors; D016896:Treatment Outcome; D018487:Ventricular Dysfunction, Left / Q000097:blood / Q000175:diagnosis / Q000209:etiology; D055815:Young Adult
chemical_list: D015415:Biomarkers; D010446:Peptide Fragments; C109794:pro-brain natriuretic peptide (1-76); D020097:Natriuretic Peptide, Brain
keywords: B-type; N-terminal pro–B-type natriuretic peptide; natriuretic peptide; renal dialysis; variability