Renal dysfunction affects NT-proBNP predictive thresholds in pulmonary hypertension

By Eleanor McDermid, Senior medwireNews Reporter

N-terminal pro-brain natriuretic peptide (NT-proBNP) remains a valid predictor in patients with pulmonary arterial hypertension (PAH) who have concomitant renal dysfunction, say researchers.

However, they had to use higher than normal thresholds for patients with renal dysfunction, particularly for predicting survival.

“In these patients elevation of NT-proBNP due to renal dysfunction has to be taken into account if NT-proBNP level is used for risk-stratification or even as treatment goal”, say researcher Hans Klose (University Medical Center Hamburg-Eppendorf, Germany) and colleagues.

Their study included 155 patients with PAH, 40 of whom had renal dysfunction, defined as an estimated glomerular filtration rate at or below 60 mL/min per 1.73 m², at the time of right heart catheterisation, NT-proBNP levels rose as kidney function declined, so the median level was significantly higher in patients with renal dysfunction than those without, at 1935 versus 573 ng/L.

Nevertheless, NT-proBNP levels correlated with patients’ haemodynamic parameters, regardless of whether they had renal dysfunction.

During follow-up lasting an average of 20.6 months, 46% of the patients experienced clinical worsening. Among patients with normal renal function, NT-proBNP levels of 1292 ng/L predicted clinical deterioration with a sensitivity of 50% and a specificity of 83%.

In patients with renal dysfunction, however, a higher threshold of 1660 ng/L was required, giving a sensitivity of 68% and a specificity of 73%. Patients with levels at or above this threshold were 4.8 times more likely than patients with lower levels to have clinical worsening after accounting for variables including age, renal function and 6-minute walk distance.

An even higher threshold was needed to predict mortality in these patients. During an average 39 months of follow-up, 33% of patients with renal insufficiency died, and this was best predicted by a NT-proBNP threshold of 2212 ng/L, which gave a sensitivity of 62% and a specificity of 71%.

However, levels above this threshold were not associated with survival after accounting for factors including 6-minute walk distance and World Health Organization functional class.

“Thus, in these patients NT-proBNP seems to represent [a] valid clinical marker and facilitate clinical decision-making”, the team concludes in PLoS One.

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