Abstract
BACKGROUND AND AIMS: Limited data are available to assess oral diuretic response in outpatients with heart failure (HF). The natriuretic response prediction equation (NRPE) predicts natriuresis following a loop diuretic dose using a urine sample 2 h after the dose and was validated to accurately predict intravenous diuretic response. The primary aim was to validate the NRPE's assessment of oral diuretic response in patients with HF. METHODS: The NRPE was evaluated in two HF patient cohorts receiving oral loop diuretics: Mechanisms of Diuretic Resistance (MDR) and TRANSFORM-Mechanism. Participants received their home oral loop diuretic followed by a supervised timed urine collection including spot urine samples at 1 and 2 h. Patients quantified their self-assessed diuretic response (urine volume) via a standardized survey. A poor diuretic response was defined as cumulative natriuresis < 50 mmol over the study visit. RESULTS: The MDR cohort included 318 oral diuretic administrations from 237 patients. The NRPE predicted a poor natriuretic response with an area under the curve (AUC) of .87 [95% confidence interval (CI) .83-.91] and similar accuracy to the previously validated intravenous NRPE performance (P = .16). Patient's ability to self-estimate their diuretic response was poor with an AUC of .57 (95% CI .44-.70) and significantly worse than the oral NRPE (P < .001). In TRANSFORM-Mechanism (110 oral diuretic administrations), the NRPE had similar operating characteristics (AUC .89, 95% CI .80-1.0) for poor diuretic response. CONCLUSIONS: Natriuretic response to an oral diuretic can be rapidly and accurately assessed with a urine sample collected 2 h after an oral diuretic dose and the NRPE.