NT-proBNP variation in stable pulmonary arterial hypertension patients.

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Introduction: NT-proBNP is used for diagnosis and risk stratification in patients with pulmonary arterial hypertension (PAH). Consideration of its biological variation is essential in the interpretation of serial measurements. We aimed to study the variation of NT-proBNP over serial measurements in stable PAH patients. Methods: Stable PAH defined as stable NYHA class I or II, no reduction of 6MWD more than 15% and no medication changes in a 2-year period. Coefficient of variation (CV) was defined as the (standard deviation/mean)*100 of NT-proBNP measurements during the first year of clinical stability. To assess the influence of the magnitude of NT-proBNP concentrations on the CV, we performed a correlation. Results: We studied 28 stable PAH patients, 60% of the female gender, with a mean age of 52 years. In terms of etiology 28% were classified as chronic thromboembolic pulmonary hypertension, followed by 21% associated with connective tissue diseases. At baseline the mean 6MWD was 470 meters [324-661] and 60% of patients were on mono vasodilator therapy. The median and interquartile range of baseline (after 3 months of stable treatment) NT-proBNP concentration was 184 [55-491] ng/mL. The overall mean CV was 24±13%. There was no significant correlation between CV and absolute NT-proBNP concentrations (coef= -0.12; p=0.34). Conclusion: In stable PAH patients, we observed a significant variation of NT-proBNP concentrations in serial measurements, which did not differ across absolute concentration range. Our data underline the need to consider biological variation to correctly interpret this useful and validated biomarker in PAH management.

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