Performance of Methods to Assess Kidney Function in a Predominantly Overweight Sample of Patients with Liver Disease

Figures & data

Table 1.  Methods used to assess kidney function.

Method	Abbreviations	Equation	Definitions
1^a Plasma decay method	^125I-CL, V-CL		AUC = area under plasma concentration versus time curve
2^a Urine collection method	^125I-Urine, CLCr Urine		U = urine concentrationP = plasma concentrationVol = volume of urine collectedTime = urine collection period
3 Hoek formula^22	Cystatin C GFR		Cys C = Cystatin C concentration
4^a Cockcroft–Gault^7	CG		Total body weight (TBW) in kilograms
5 MDRD equation^8	MDRD		AA = African-American

Notes: ¹²⁵I-CL, radiolabeled iothalamate clearance determined using the plasma decay method; ¹²⁵I-Urine, radiolabeled iothalamate clearance determined using the urine collection method; V-CL, vancomycin clearance; CLCr Urine, measured creatinine clearance; Cystatin C GFR, estimate of GFR using the cystatin C-based Hoek formula;²² CG, Cockcroft–Gault equation; MDRD, four-variable Modification of Diet in Renal Disease equation; GFR, glomerular filtration rate.

^aValues for methods 1, 2, and 4 were expressed in mL/min/1.73 m² by multiplying the calculated value by 1.73 m²/BSA, where BSA is the body surface area of the patient in m².

Table 2.  Patient characteristics.

Patient #	Cause of liver disease	Sex	Race	Age (years)	TBW (kg)	IBW (kg)	BMI (kg/m^2)	BSA (m^2)	SCr (mg/dL)	Alb (g/dL)	BUN (mg/dL)	INR	Bilirubin (mg/dL)	Cystatin C (mg/L)	MELD
1	Hepatitis C	F	AA	52	73	50	29	1.79	0.7	3.3	10	1.46	1.6	0.6	12
2	Laennec’s cirrhosis	M	W	52	99	83	28	2.28	1.1	3.5	11	1.32	1.5	1.0	12
3	Steatohepatitis	F	W	47	100	60	35	2.16	1.1	2.5	3	1.78	2.3	1.3	17
4	Primary biliary cirrhosis	F	AA	53	173	61	60	2.86	1.4	2.9	21	1.13	0.9	1.8	11
5	Primary biliary cirrhosis	F	W	43	47	51	18	1.44	0.7	3.2	9	1.07	4.8	1.0	13
6	Hepatitis C	M	W	52	61	62	22	1.67	1.1	2.9	23	1.23	0.7	1.9	10
7	Hepatitis B	M	W	55	84	69	28	2.01	1.7	1.8	27	1.40	1.6	1.9	17
8	Nonalcoholic steatohepatitis (NASH)	F	W	65	82	51	33	2.82	1.7	3.5	17	1.12	0.6	2.0	13
Mean (SD)	–	–	–	52 (6)	90 (38)	61 (11)	37 (19)	2.13 (0.51)	1.2 (0.4)	3.0 (0.6)	9.5 (6.9)	1.3 (0.2)	1.8 (1.4)	1.4 (0.5)	13 (3)

Note: AA, African-American; W, white; TBW, total body weight; IBW, ideal body weight; BMI, body mass index; BSA, body surface area; SCr, serum creatinine; Alb, albumin; BUN, blood urea nitrogen; MELD, Model for End-Stage Liver Disease.

Table 3.  Measured GFR and surrogate estimates of kidney function by patient (expressed in mL/min/1.73 m²).

Patient #	^125I-Urine	^125I-CL	CLCr Urine	V-CL^a	MDRD	CG	Cystatin C GFR
1	116	124	105	111	113	104	122
2	101	119	105	86	75	83	73
3	92	87	90	86	57^b	80	56^b
4	53	57	58	25^b	50	76^b	41
5	120	106	94	93	97	93	79
6	50	63	64	56	75^b	70	39
7	35	72^b	51^b	66^b	45	50^b	39
8	23	32^b	34^b	36^b	32^b	58^b	35^b
Mean (SD)	74 (38)	83 (32)	75 (27)	70 (30)	68 (27)	77 (18)	61 (30)
P versus ^125I-urine	–	0.195	0.578	0.984	0.523	0.617	0.195

Notes: GFR, glomerular filtration rate; CG, Cockcroft–Gault equation; MDRD, Modification of Diet in Renal Disease equation.

^aV-CL for patient #4 has been omitted from statistical analysis.

^bValues not within 30% of ¹²⁵I-Urine.

Figure 1.  Box plot of the difference in the mean ¹²⁵I-Urine and other assessment methods. The line within the box marks the median. Error bars above and below the box indicate the 90th and 10th percentiles.

Figure 2.  Bland–Altman plots of the relationship between ¹²⁵I-Urine and (A) ¹²⁵I-CL; (B) CLCr Urine; (C) V-CL; (D) MDRD; (E) CG-TBW; and (F) Cystatin C. Solid bar indicates the mean difference or bias. Dashed lines indicate the upper and lower limits of the interval of agreement (±1SD).

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