Spot Urine Estimations Are Equivalent to 24-Hour Urine Assessments of Urine Protein Excretion for Predicting Clinical Outcomes

Table 2

Equations for converting spot estimates and 24 hr urine measurements.

(a) Conversion predicting equations

Equations	value
Log ⁡24 hr urine protein excretion (g) = −0.617019 + 0.7150918 × Log UPCR (mg/mg)	<0.001
Log ⁡24 hr urine albumin excretion (g) = −0.800153 + 0.8257142 × Log UACR (mg/mg)	<0.001
Log UACR (mg/mg) = −0.656352 + 1.3881178 × Log UPCR (mg/mg)	<0.001
Log UPCR (mg/mg) = 0.3216439 + 0.6394674 × Log UACR (mg/mg)	<0.001
Log UACR (mg/mg) = −0.270587 + 1.2870223 × Log ⁡24 hr urine protein excretion (g)	<0.001

(b) Performance of conversion equations using an external validation dataset ( = 45)

Predictor	Predicted variable	Predicted value	Measured value	value	Correlation (95% CI)
UPCR (mg/mg)	24 hr urine protein excretion (g)	0.74 (0.67–0.82)	0.38 (0.14–0.92)	0.0051	0.63 (0.41–0.78)
UACR (mg/mg)	24 hr urine albumin excretion (g)	0.91 (0.87–0.94)	0.21 (0.02–0.58)	<0.001	0.55 (0.31–0.73)
UPCR (mg/mg)	UACR (mg/mg)	0.01 (0.00–0.03)	0.03 (0.00–0.08)	<0.001	0.97 (0.95–0.98)
UACR (mg/mg)	UPCR (mg/mg)	0.15 (0.04–0.29)	0.05 (0.02–0.13)	<0.001	0.95 (0.91–0.97)
24 hr urine protein excretion (g)	UACR (mg/mg)	0.22 (0.06–0.69)	0.03 (0.00–0.08)	<0.001	0.81 (0.68–0.89)

Reported as median (25th–75th percentile); value of the difference between predicted and measured values; Pearson correlation (95% confidence interval).