Table 3.
Comparison of Estimates Obtained From 24‐Hour Urine and Spot Urine Samples
| Equation | Salt Intake, g/d (mean, SD) | Difference (95% CI) | P Value | |||
|---|---|---|---|---|---|---|
| No. | Baseline | No. | Follow‐Up | |||
| 24‐h urine | 88 | 9.43 (3.69) | 73 | 7.44 (4.09) | −1.99 (−3.20 to −0.78) | .002 |
| INTERSALT equation | 509 | 8.48 (2.13) | 511 | 8.05 (2.11) | −0.43 (−0.69 to −0.17) | .001 |
| Tanaka equation | 509 | 9.94 (2.64) | 511 | 9.21 (2.84) | −0.73 (−1.06 to −0.39) | <.001 |
| Mage equation | 509 | 10.07 (8.50) | 511 | 8.74 (8.25) | −1.34 (−2.37 to −0.31) | .011 |
| Kawasaki equation | 509 | 13.98 (5.06) | 511 | 12.88 (5.19) | −1.09 (−1.72 to −0.46) | .001 |
| Simple equationa | 509 | 12.37 (9.85) | 511 | 10.64 (9.38) | −1.73 (−2.92 to −0.55) | .004 |
Abbreviations: CI, confidence interval; INTERSALT, International Cooperative Study on Salt, Other Factors, and Blood Pressure; SD, standard deviation.
Based on the equation used by Mann and Gerber (2010)19 to estimate 24‐hour sodium excretion from spot urine samples. The equation predicts the 24‐hour estimate by calculating the ratio of sodium and creatinine in the spot sample then multiplying this ratio by the individuals’ measured 24‐hour creatinine excretion. In this paper, the equation was modified such that 24‐hour creatinine excretion was predicted using Tanaka's formula: 24‐hour predicted creatinine (mg/d)=−2.04×age+14.89×weight+16.14×height−2244.45. In addition, 24‐hour predicted sodium was computed using the formula: [Spot Na (mmol/l) ÷ (Spot Crea (mg/dL)×10)]×24‐hour predicted creatinine (mg/d).