Utility of cystatin C-derived equations for evaluation of residual renal function in peritoneal dialysis patients

Figures & data

Table 1. Baseline characteristics of study participants.

Age (years)	56.5.2 ± 16.5
Sex (female/male)	39/37
Underlying kidney disease, n (%)
Diabetes	28 (36.8)
Hypertension	19 (25.0)
Diabetes + Hypertension	10 (13.2)
Nephrotic syndrome	4 (5.3)
Lupus nephritis	3 (3.9)
Other	12 (15.8)
Time on peritoneal dialysis (months)	24 (20–26)
BMI (kg/m^2)	23.6 ± 4.7
Serum CRP (mg/L)	5.0 ± 1.2
Serum TSH (mU/L)	3.6 ± 1.5
Serum albumin (g/dL)	3.2 ± 0.6
Serum creatinine (mg/dL)	7.8 ± 3.3
Serum urea (mg/dL)	101.3 ± 34.1
Urine creatinine (mg/dL)	19.3 ± 33.9
Urine urea (mg/dL)	32.0 ± 26.5
Serum cystatin C (mg/L)	5.0 ± 1.2
Peritoneal equilibration test, n (%)
High	41 (54.0)
High average	21 (27.6)
Low average	11 (14.5)
Low	3 (3.9)
Kt/V urea
Peritoneal	1.5 ± 0.4
Renal	0.5 ± 0.6
Total	2.0 ± 0.8

Figure 1. Bland–Altman scatter plots between RRF and GFR estimations methods of (A) CKD-EPI, (B) Hoek’s, and (C) Yang’s. Notes: Horizontal lines delineate mean difference along with upper and lower limits of agreement. RRF, residual renal function; GFR, glomerular filtration rate; CKD-EPI, chronic kidney disease epidemiology collaboration.

Table 2. Correlation analysis for cystatin C and serum creatinine with clinical parameters and indicators of dialysis adequacy.

	Cystatin C				Serum creatinine
	Female		Male		Female		Male
	r	p Value	r	p Value	r	p Value	r	p Value
Age	0.211	0.197	0.173	0.305	0.351	0.028	0.334	0.0.43
BMI (kg/m^2)	0.019	0.910	0.062	0.715	0.142	0.389	0.144	0.396
Serum CRP (mg/L)	0.163	0.322	0.101	0.554	0.051	0.758	0.014	0.932
Serum TSH (mU/L)	−0.037	0.822	0.092	0.586	0.074	0.656	0.003	0.987
Serum albumin (g/dL)	0.247	0.130	0.023	0.894	0.138	0.402	0.113	0.0506
Kt/V urea (peritoneal)	0.048	0.770	−0.136	0.422	−0.281	0.083	0.043	0.802
Kt/V urea (renal)	−0.131	0.427	−0.058	0.733	−0.309	0.056	−0.372	0.023
Kt/V urea (total)	−0.044	0.792	−0.104	0.541	−0.371	0.020	−0.283	0.089
RRF (mL/min/1.73 m^2)	0.129	0.433	0.367	0.025	−0.322	0.039	−0.281	0.092

Note: r, correlation coefficient; BMI, body mass index; CRP, C-reactive protein; TSH, thyroid stimulating hormone; RRF, residual renal function.

Table 3. Agreement analysis between estimated GFR values of cystatin C and CKD-EPI and residual renal function.

			Difference		Accuracy (%)
GFR method	Mean ± SD (mL/min/1.73 m^2)	(95% CI) (mL/min/1.73 m^2)	Limits of agreement (mL/min/1.73 m^2)	p Value^a	Within 30%	Within 50%
CKD-EPI	7.4 ± 4.0	6.7 (5.9–7.5)	−0.4–13.8	<0.001	5.3	7.9
Hoek’s	4.1 ± 1.4	3.4 (2.9–3.9)	−1.1–7.9	<0.001	10.5	19.7
Yang’s	4.5 ± 1.5	3.8 (3.3–4.3)	−0.4–8.0	<0.001	9.2	11.8

Notes: ^aTesting the hypothesis whether difference (95% CI) contains 0.

GFR, glomerular filtration rate; CKD-EPI, chronic kidney disease epidemiology collaboration.