Does casual urine Na/K ratio predict 24 h urine Na/K ratio in treated hypertensive patients? Comparison between casual urine voided in the morning vs. 24 h urine collected on the previous day

The urine sodium-to-potassium (Na/K) ratio is associated with blood pressure and cardiovascular diseases. A single urine sample is preferable for determining the Na/K ratio in clinical practice. We evaluated whether the Na/K ratio measured using morning casual urine samples predicts the ratio measured using the preceding 24 h urine sample in patients with hypertension. The study included 187 hypertensive patients (mean age 66.1 years, 52.4% female) whose Na and K concentrations were measured both in 24 h (24Na/K) and casual urine the next morning (CNa/K). The Na/K ratios were 3.54 ± 1.5 in 24NaK and 2.63 ± 1.9 in CNa/K. The two estimates showed a significant positive correlation (r = 0.49, p