Page 105 - Biomarkers for risk stratification and guidance in heart failure

Chapter 5
METHODS
Study Design and Study Population
This was a post hoc analysis of patients included in the PRIMA (Can PRo-brain- natriuretic peptide-guided therapy of chronic heart failure IMprove heart fAilure morbidity and mortality?) study, a prospective randomized multicenter study assessing the effect of management of chronic HF guided by individual NT-proBNP targets.8 Inclusion criteria have been published previously.8 In short, patients were included during hospital admission for acute HF. NT-proBNP concentration at admission was required to be ≥1,700 pg/mL, and included patients also needed to demonstrate a decrease in NT-proBNP concentration of at least 10% with a minimum of 850 pg /mL during admission. At discharge, patients were randomized to outpatient treatment that was either clinically-guided where NT-proBNP was measured but not revealed to the physician, or to outpatient treatment where NT- proBNP levels were provided to guide therapy. The follow-up period was up to 2 years. For the present analysis, patients with outpatient NT-proBNP concentration available 1 month after hospital discharge were included. As a result, patients not attending the outpatient clinic 1 month after discharge (because of death, readmission, or any other reason) were not included. All events occurring before the outpatient visit 1 month after hospital discharge were censored.
Definition of Study End Points
Primary outcome measures were mortality and the combined end point of HF readmission or mortality within the follow-up period after the outpatient visit 1 month after discharge. Secondary end points encompassed the primary end points reached at 90, 180, and 365 days of follow-up.
Statistical Analysis
Data are presented as frequencies, mean ±SD, or median (interquartile range \[IQR\]). Comparisons between groups were performed with the use of Fischer exact test for categoric data and 1-way analysis of variance or Kruskal-Wallis H test for continuous data, as appropriate. Glomerular filtration rate was estimated (eGFR) with the use of the Modified Diet in Renal Disease equation.9
Univariate Cox proportional hazard regression analysis was performed to assess clinical covariates associated with mortality. Spearman rank correlations where used to test correlations among the various NT-proBNP parameters.
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