BMJ Open Respiratory Research (Jul 2024)

Sendaway capillary NT-proBNP in pulmonary hypertension

  • Eleanor Morris,
  • Stephen J Wort,
  • Martin K Johnson,
  • James L Lordan,
  • Daniel S Knight,
  • Chloe Roddis,
  • Charlotte Durrington,
  • Harrison D Stubbs,
  • John Cannon,
  • Emily Knightbridge,
  • Wendy Gin-Sing,
  • Fiona Massey,
  • Ruta Virsinskaite,
  • Eleanor Sear,
  • Joy Apple-Pinguel

DOI
https://doi.org/10.1136/bmjresp-2023-002124
Journal volume & issue
Vol. 11, no. 1

Abstract

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Background N-terminal pro-B-type natriuretic peptide (NT-proBNP) is a biomarker of cardiac ventricular wall stress that is incorporated into pulmonary hypertension (PH) risk stratification models. Sendaway sampling may enable patients to perform NT-proBNP tests remotely. This UK-wide study aimed to assess the agreement of sendaway NT-proBNP with standard venous NT-proBNP and to assess the effect of delayed processing.Methods Reference venous NT-proBNP was collected from PH patients. Samples for capillary and venous sendaway tests were collected contemporaneously, mailed to a reference laboratory and processed at 3 and 7 days using a Roche Cobas e411 device. Differences in paired measurements were analysed with Passing-Bablok regression, percentage difference plots and the % difference in risk strata.Results 113 patients were included in the study. 13% of day 3 capillary samples were insufficient. Day 3 capillary samples were not equivalent to reference samples (Passing Bablok analysis slope of 0.91 (95% CI 0.88 to 0.93) and intercept of 6.0 (95% CI 0.2 to 15.9)). The relative median difference was −7% and there were acceptable limits of agreement. Day 3 capillary NT-proBNP accurately risk stratified patients in 93.5% of cases. By comparison, day 3 venous results accurately risk stratified patients in 90.1% of cases and were equivalent by Passing-Bablok regression. Delayed sampling of sendaway tests led to an unacceptable level of agreement and systematically underestimated NT-proBNP.Conclusions Sendaway NT-proBNP sampling may provide an objective measure of right ventricular strain for virtual PH clinics. Results must be interpreted with caution in cases of delayed sampling.