Longitudinal assessment of measured and estimated glomerular filtration-rate in autosomal dominant polycystic kidney disease: Real practice experience

Table 1 Main baseline demographic and clinical characteristics of the study sample, n (%)

Variable	n = 37
Age (years)
mean ± SD	40.2 ± 15.3
Median (IqR)	37.0 (31.0-50.0)
Body mass index (kg/m2)
mean ± SD	25.4 ± 5.8
Median (IqR)	24.5 (21.8-27.4)
Gender
Female	19 (51.4)
Male	18 (48.6)
Diabetes mellitus
Yes	0 (0.0)
No	37 (100.0)
Dyslipidemia
Yes	4 (11.1)
No	32 (88.9)
HBP
Yes	22 (59.5)
No	15 (40.5)
HBP controlled
Yes	21 (95.5)
No	1 (4.5)
Systolic blood pressure (mmHg)
mean ± SD	130.9 ± 15.5
Median (IqR)	131.0 (118.8-140.0)
Diastolic blood pressure (mmHg)
mean ± SD	79.4 ± 9.0
Median (IqR)	80.0 (72.8-84.3)
Cardiovascular events
Yes	0 (0.0)
No	37 (100.0)
Smoker status
Never	32 (86.5)
Former	2 (5.4)
Current	3 (8.1)
Family history of autosomal dominant polycystic kidney disease
Yes	31 (86.1)
No	5 (13.9)

HBP: High blood pressure; IqR: Interquartile range.

Table 2 Concordance correlation coefficient between the measured glomerular filtration rate (used as reference method) and the estimated glomerular filtration rate (by chronic kidney disease epidemiology collaboration, modification of diet in renal disease and creatinine clearance formulas) in the overall study sample and according to the median split baseline measured glomerular filtration rate groups

	mGFR (reference), overall study sample (n = 37)
	CCC (95%CI)	Precision	Accuracy
CKD-EPI	0.576 (0.318-0.754)	0.585	0.983
MDRD	0.457 (0.223-0.641)	0.582	0.786
CrCl	0.598 (0.376-0.755)	0.697	0.858
	mGFR ≤ 80 (n = 17)
	CCC (95%CI)	Precision	Accuracy
CKD-EPI	0.315 (-0.038 to 0.599)	0.425	0.741
MDRD	0.356 (-0.069 to 0.672)	0.414	0.862
CrCl	0.418 (0.064-0.679)	0.599	0.698
	mGFR > 80 (n = 20)
	CCC (95%CI)	Precision	Accuracy
CKD-EPI	0.429 (0.069-0.690)	0.515	0.833
MDRD	0.277 (0.033-0.490)	0.529	0.524
CrCl	0.315 (-0.037 to 0.597)	0.423	0.745

CCC: Concordance correlation coefficient; CKD-EPI; Chronic kidney disease epidemiology collaboration; CrCl: Creatinine clearance; MDRD: Modification of diet in renal disease; mGFR: Measured glomerular filtration rate.

Table 3 Measured and estimated month-6 glomerular filtration rates changes versus baseline in the overall study autosomal-dominant polycystic kidney disease patients (n = 37) and ranked according to measured glomerular filtration rate ≤ 80 (n = 17) and > 80 (n = 20) mL/minute

		Glomerular filtration rate (mL/minute)
		Overall (n = 37)	mGFR ≤ 80 (n = 17)	mGFR > 80 (n = 20)
Iohexol	Baseline (mean ± SD)	85.6 ± 24.6	65.6 ± 10.2	102.7 ± 19.8
	Month-6 (mean ± SD)	81.2 ± 26.2	63.2 ± 16.1	96.6 ± 16.3
	Difference
	mean ± SD	-4.4 ± 10.3	-2.4 ± 9.5	-6.1 ± 10.8
	95%CI	-7.8 to -1.0	-7.2 to 2.5	-11.2 to -1.1
	P value	0.0132a	0.2842b	0.0136b
Chronic kidney disease epidemiology collaboration	Baseline (mean ± SD)	81.3 ± 23.7	71.2 ± 20.8	89.9 ± 23.0
	Month-6 (mean ± SD)	79.0 ± 23.9	69.1 ± 24.2	87.5 ± 20.6
	Difference
	mean ± SD	-2.3 ± 12.7	-2.2 ± 15.2	-2.4 ± 10.4
	95%CI	-6.5 to 2.0	-10.0 to 5.7	-7.3 to 2.5
	P value	0.2824a	0.4691b	0.4939b
Modification of diet in renal disease	Baseline (mean ± SD)	71.7 ± 18.9	63.6 ± 17.6	78.2 ± 17.7
	Month-6 (mean ± SD)	71.2 ± 19.2	63.5 ± 18.6	77.4 ± 17.7
	Difference
	mean ± SD	-0.5 ± 9.3	-0.1 ± 11.9	-0.8 ± 6.9
	95%CI	-3.6 to 2.7	-6.4 to 6.2	-4.0 to 2.3
	P value	0.7560a	0.7119b	0.5196b
Creatinine clearancec	Baseline (mean ± SD)	100.6 ± 34.1	74.0 ± 15.4	127.3 ± 27.4
	Month-6 (mean ± SD)	98.2 ± 34.0	77.6 ± 19.2	118.9 ± 33.5
	Difference
	mean ± SD	-2.4 ± 24.5	3.6 ± 10.3	-8.4 ± 32.7
	95%CI	-12.7 to 8.0	-2.9 to 10.1	-29.2 to 12.4
	P value	0.7642b	0.3668b	0.4697b

^aPaired samples t student test.

^bWilcoxon test.

^cMonth-6 measurements available in 24 patients in the overall study sample, 12 in the measured glomerular filtration rate (mGFR) ≤ 80 and in the mGFR > 80 groups, respectively.

mGFR: Measured glomerular filtration rate.