Supplemental Table 1. Patient Characteristics

Supplemental Table 1. Patient Characteristics

Characteristic

/

N = 163

Age (yr)

/

53 ± 12

Male (n [%])

/

110 (67)

Race (n [%])

/

White

/

147 (90)

Black

/

5 (3)

Asian

/

6 (4)

other

/

5 (3)

Weight (kg)

/

78.7 ± 17.6

Height (cm)

/ 167.6 ± 9.6

Body surface area (m2)

/ 1.88 ± 0.23

Living donor (n [%])

/ 59 (36)

Time post-transplant (yr)

/ 8.0 ± 10.2

Primary transplant (n [%])

/ 141 (87)

Causes of renal disease (n [%])

Diabetes mellitus

/ 22 (13)

Polycystic kidney disease

/ 22 (13)

Glomerulonephritis

/ 45 (28)

Hypertension

/ 9 (6)

Other

/ 65 (40)

Supplemental Table 1. Patient characteristics (continued)

Medication (n [%])

Prednisone

/ 161 (99)

Cyclosporine

/ 81 (50)

Tacrolimus

/ 63 (39)

Sirolimus

/ 6 (4)

Mycophenolate Mofetil

/ 108 (66)

Azathioprine

/ 26 (16)

Trimethoprim-sulfamethoxazole

/ 29 (18)

Supplemental Table 2. Measurements of renal function

Characteristic

/

N = 163

Serum creatinine (umol/L)

/ 148 ± 66

Serum urea (mmol/L)

/ 10 ± 6

Serum BTP (mg/L)

Mean

/ 1.26 ± 0.71

Median

/ 1.08

Range

/ 0.42 – 4.90

Abbreviated MDRD GFR (ml/min/1.73m2)

/ 50 ± 20

DTPA-GFR (ml/min/1.73m2)

/ 59 ± 23

Chronic kidney disease stage (n [%])

Stage 1, GFR ≥ 90 ml/min/1.73m2

/ 16 (10)

Stage 2, GFR 60-89 ml/min/1.73m2

/ 64 (39)

Stage 3, GFR 30-59 ml/min/1.73m2

/ 68 (42)

Stage 4, GFR 15-29 ml/min/1.73m2

/ 12 (7)

Stage 5, GFR <15 ml/min/1.73m2

/ 3 (2)

Supplemental Table 3. Bias, precision and accuracy of creatinine and BTP estimatesa

CKD Stage / Bias / Precision / Accuracy Within
10% 30%
10% 30%
bEquation #1 / 1 / -14.9 / 12.0 / 19 / 100
2 / -1.6 / 12.4 / 47 / 98
3 / 2.0 / 7.7 / 43 / 87
4&5 / 3.9 / 6.3 / 20 / 53
All / -0.9 / 11.3 / 40 / 88
cEquation #2 / 1 / -15.1 / 14.5 / 31 / 100
M / 2 / -2.6 / 11.4 / 39 / 94
3 / 2.1 / 7.5 / 49 / 88
4&5 / 4.0 / 7.1 / 40 / 60
All / -1.2 / 11.1 / 42
2 / 88
Abbreviated MDRD / 1 / -25.7 / 16.6 / 25 / 50
2 / -11.4 / 10.6 / 28 / 83
3 / -4.5 / 9.4 / 21 / 82
4&5 / -3.1 / 4.9 / 27 / 67
All / -9.5 / 12.5 / 25 / 78

aBias was defined as the mean difference between measured (99mTc-DTPA) and estimated GFR (estimated GFR-measured GFR); Precision was defined as the standard deviation of the difference between measured (99mTc-DTPA) and estimated glomerular filtration rate; Precision, bias and mean GFR were expressed as ml/min/1.73m2; Accuracy was defined as the proportion of values that were within 10% or 30% of the measured (99mTc-DTPA) GFR

bEquation #1: 112.1 x BTP-0.662x Urea-0.280 x (0.880 if the patient is female), BTP in mg/L, urea in mmol/L, estimated GFR in ml/min/1.73m2

cEquation #2: 167.8 x BTP-0.758x Creatinine-0.204 x (0.871 if the patient is female),

BTP in mg/L, creatinine in umol/L, estimated GFR in ml/min/1.73m2

Supplemental Table 4-Receivor Operating Characteristic Analysis

GFR Cutoff
ml/min/1.732 / Abbreviated MDRD GFR
ml/min/1.732 / Equation #1 BTP GFR
ml/min/1.732
AUC / Sensitivity / Specificity / AUC / Sensitivity / Specificity
30
(95% CI) / 0.76
(0.55-0.91) / 66.7
(38.4-88.1) / 77.8
(40.1-96.5) / 0.88
(0.64-0.98) / 90
(55.5-98.3) / 75
(35.0-96.1)
40
(95% CI) / 0.97
(0.89-0.99) / 87.5
(71.0-96.4) / 96.6
(82.2-99.4) / 0.99
(0.90-0.99) / 92.9
(76.5-98.9) / 100
(78-100)
50
(95% CI) / 0.88
(0.79-0.94) / 69.5
(56.1-80.8) / 97.2
(85.4-99.5) / 0.90
(0.81-0.96) / 85.2
(72.9-93.4) / 81.2
(54.3-95.7)
60
(95% CI) / 0.91
(0.84-0.95) / 90.1
(81.5-90.6) / 74.4
(57.9-86.9) / 0.91
(0.84-0.96) / 80.5
(69.9-88.7) / 90.9
(70.8-98.6)

There were no statistically significant differences between the MDRD equation and the BTP equation at any of the DTPA GFR cutoffs (p>0.05)