External validation of the natriuretic response prediction equation to discriminate diuretic response in heart failure

Aims: Incomplete decongestion due to lack of titration of diuretics to effective doses is a common reason for readmission in patients with acute decompensated heart failure (ADHF). The natriuretic response prediction equation (NRPE) is a novel tool that proved to be rapid and accurate to predict natriuretic response and does not need urine collection. However, the NRPE has not been externally validated. The goal of this study was to externally validate the discrimination capacity of the NRPE in patients with ADHF and fluid overload.

Methods and results: Patients admitted with ADHF who required intravenous loop diuretics were included. A spot urine sample was obtained ~2 h following diuretic administration, and a timed 6-h urine collection by study staff was carried out. Urine sodium and urine creatinine from the spot urine sample were used to predict the 6-h natriuretic response using the NRPE. The primary goal was to validate the NRPE to discriminate poor loop diuretic natriuretic response (sodium output <50 mmol in the 6 h following diuretic administration). The NRPE was compared with urine sodium and measured urine output which are the methods currently recommended by international guidelines to assess diuretic response. Eighty-seven diuretic administrations from 49 patients were analysed. Mean age of patients was 57 ± 17 years and 67% were male. Mean estimated glomerular filtration rate was 65 ± 28 mL/min/1.73 m², and ejection fraction was 35 ± 15%. Median dose of intravenous furosemide equivalents administered the day of the study was 80 mg (IQR 40 - 160). Poor natriuretic response occurred in 39% of the visits. The AUC of the NRPE to predict poor natriuretic response during the 6-h urine collection was 0.91 (95% CI 0.85-0.98). Compared with the NRPE, spot urine sodium concentration (AUC 0.75) and urine output during the corresponding nursing shift (AUC 0.74) showed lower discrimination capacity.

Conclusions: In this cohort of patients with ADHF, the NRPE outperformed spot urine sodium concentration and all other metrics related to diuretic response to predict poor natriuretic response. Our findings support the use of this equation at other settings to allow rapid and accurate prediction of natriuretic response.