J Clin Med Res

Journal of Clinical Medicine Research, ISSN 1918-3003 print, 1918-3011 online, Open Access

Article copyright, the authors; Journal compilation copyright, J Clin Med Res and Elmer Press Inc

Journal website http://www.jocmr.org

Original Article

Volume 12, Number 7, July 2020, pages 443-447

Diagnostic Accuracy of Single Spot Urine for Detecting Renal Uric Acid Underexcretion in Men

Figure 1. The ROC curve of the UACR, FCU, and the Simkin index for predicting renal UA underexcretion. ROC: receiver operating characteristic; UACR: urinary uric acid to creatinine ratio; FCU: fractional clearance of urate.

**Table 1.** Clinical Characteristic of the Participants With or Without Renal UA Underexcretion
Variables	Renal UA clearance (mL/min)	P value
Mean (standard deviation), median (25%, 75%), or %. BMI: body mass index; AST: aspartate aminotransferase; ALT: alanine transferase; GGT: γ-glutamyl transferase; UA: uric acid; SCr: serum creatinine; eGFR: estimated glomerular filtration rate; UACR: urinary uric acid to creatinine ratio; FCU: fraction clearance of urate.
Age, years	46.4 (12.0)	56.1 (10.4)	< 0.001
BMI, kg/m²	24.4 (3.3)	24.4 (2.8)	0.982
AST, IU/L	25.8 (8.2)	21.7 (10.1)	0.067
ALT, IU/L	30.5 (19.1)	24.9 (19.3)	0.221
GGT, IU/L	43.7 (31.1)	38.3(29.2)	0.451
Serum UA, mg/dL	6.7 (0.5)	6.9 (0.6)	0.174
SCr, mg/dL	0.91 (0.13)	0.97 (0.12)	0.026
eGFR, mL/min/1.73 m²	74.29 (12.78)	64.34 (9.01)	< 0.001
UACR	0.52 (0.07)	0.40 (0.08)	< 0.001
FCU	0.07 (0.01)	0.06 (0.01)	< 0.001
Simkin index	0.47 (0.08)	0.39 (0.08)	< 0.001
Alcohol consumption, g/week	56.0 (0, 134.4)	14.0 (0, 128.2)	0.416
Medication, %
Hypertension	6.1	7.5	> 0.999
Diabetes	6.1	0	0.201

Table 1. Clinical Characteristic of the Participants With or Without Renal UA Underexcretion

Variables

Renal UA clearance (mL/min)

P value

≥ 7.3 (n = 33)

< 7.3 (n = 40)

Mean (standard deviation), median (25%, 75%), or %. BMI: body mass index; AST: aspartate aminotransferase; ALT: alanine transferase; GGT: γ-glutamyl transferase; UA: uric acid; SCr: serum creatinine; eGFR: estimated glomerular filtration rate; UACR: urinary uric acid to creatinine ratio; FCU: fraction clearance of urate.

Age, years

46.4 (12.0)

56.1 (10.4)

< 0.001

BMI, kg/m²

24.4 (3.3)

24.4 (2.8)

0.982

AST, IU/L

25.8 (8.2)

21.7 (10.1)

0.067

ALT, IU/L

30.5 (19.1)

24.9 (19.3)

0.221

GGT, IU/L

43.7 (31.1)

38.3(29.2)

0.451

Serum UA, mg/dL

6.7 (0.5)

6.9 (0.6)

0.174

SCr, mg/dL

0.91 (0.13)

0.97 (0.12)

0.026

eGFR, mL/min/1.73 m²

74.29 (12.78)

64.34 (9.01)

< 0.001

UACR

0.52 (0.07)

0.40 (0.08)

< 0.001

FCU

0.07 (0.01)

0.06 (0.01)

< 0.001

Simkin index

0.47 (0.08)

0.39 (0.08)

< 0.001

Alcohol consumption, g/week

56.0 (0, 134.4)

14.0 (0, 128.2)

0.416

Medication, %

Hypertension

6.1

7.5

> 0.999

Diabetes

6.1

0.201

**Table 2.** Comparison of the UACR, FCU and the Simkin Index for Predicting Renal UA Underexcretion
Variables	Cutoff	Sn, %	Sp, %	PPV, %	NPV, %	DA, %	+LR	-LR	AUC (95% CI)	P value^a	P value^b
UACR = UUA/UCr; FCU = (UUA × SCr)/(SUA × UCr); Simkin index = UUA × SCr/UCr. ^avs. FCU; ^bvs. Simkin index. UACR: urinary uric acid to creatinine ratio; FCU: fraction clearance of urate; Sn: sensitivity; Sp: specificity; PPV: positive predictive value; NPV: negative predictive value; DA: diagnostic accuracy; +LR: positive likelihood ratio; -LR: negative likelihood ratio; AUC: area under the curve; UUA: urine uric acid; UCr: urine creatinine; SCr: serum creatinine.
UACR	0.460	89.2	80.6	82.5	87.9	84.9	4.59	0.13	0.903 (0.830 - 0.976)	0.158	0.004
FCU	0.060	67.5	87.9	87.1	69.0	76.7	5.57	0.37	0.841 (0.749 - 0.933)	-	0.013
Simkin index	0.399	81.2	65.9	65.0	81.8	72.6	2.38	0.29	0.779 (0.673 - 0.885)	0.013	-

Table 2. Comparison of the UACR, FCU and the Simkin Index for Predicting Renal UA Underexcretion

Variables

Cutoff

Sn, %

Sp, %

PPV, %

NPV, %

DA, %

+LR

-LR

AUC (95% CI)

P value^a

P value^b

UACR = UUA/UCr; FCU = (UUA × SCr)/(SUA × UCr); Simkin index = UUA × SCr/UCr. ^avs. FCU; ^bvs. Simkin index. UACR: urinary uric acid to creatinine ratio; FCU: fraction clearance of urate; Sn: sensitivity; Sp: specificity; PPV: positive predictive value; NPV: negative predictive value; DA: diagnostic accuracy; +LR: positive likelihood ratio; -LR: negative likelihood ratio; AUC: area under the curve; UUA: urine uric acid; UCr: urine creatinine; SCr: serum creatinine.

UACR

0.460

89.2

80.6

82.5

87.9

84.9

4.59

0.13

0.903 (0.830 - 0.976)

0.158

0.004

FCU

0.060

67.5

87.9

87.1

69.0

76.7

5.57

0.37

0.841 (0.749 - 0.933)

0.013

Simkin index

0.399

81.2

65.9

65.0

81.8

72.6

2.38

0.29

0.779 (0.673 - 0.885)

0.013