Role of Residual Kidney Function and Convective Volume on Change in β2-Microglobulin Levels in Hemodiafiltration Patients

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Figure 1.
Changes in predialysis serum β2M levels by dialysis modality in patients (A) without and (B) with RKF. Bars represent 95% CI. ^#P < 0.001 (for difference between HDF and HD).
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Figure 2.
Relationship between baseline GFR and change in β2M level from baseline to 6 mo in HDF patients adjusted for participating center. Baseline GFR is subdivided in tertiles. Bars represent 95% CI. P value for trend <0.001.

Table 1.

Patient characteristics at baseline^a

	HDF (n = 199)	HD (n = 207)
Gender (% male)	62	65
Age (yr)	66 (53 to 74)	66 (55 to 75)
History of cardiovascular disease (%)	45	44
Diabetes mellitus (%)	25	20
Dialysis vintage (yr)	1.7 (0.8 to 3.4)	2.2 (1.1 to 4.1)
Body mass index (kg/m²)	24.9 ± 4.7	25.0 ± 4.2
Systolic blood pressure (mmHg)	147 ± 21	150 ± 21
Diastolic blood pressure (mmHg)	76 ± 13	77 ± 11
Vascular access (% arteriovenous fistula)	76	80
Treatment time (min)	240 (210 to 240)	240 (210 to 240)
Blood flow (ml/min)	302 ± 37	299 ± 43
Dialysis Kt/V_urea	1.39 ± 0.22	1.36 ± 0.17
RKF (%)^b	58	55
Urinary volume (ml/24 h)^c	700 (288 to 1150)	750 (350 to 1210)
GFR (ml/min/1.73 m²)^c,^d	3.1 (1.3 to 5.6)	3.3 (1.1 to 5.4)
Hemoglobin (mmol/L)	7.4 ± 0.8	7.4 ± 0.7
Phosphorus (mmol/L)	1.69 ± 0.52	1.63 ± 0.49
Albumin (g/L)	36.5 ± 4.6	36.7 ± 4.5
β2M (mg/L)	29.5 ± 12	31.9 ± 13

↵a Values represent mean ± SD, median (interquartile range), or proportion (%). To convert hemoglobin in mmol/L to g/dl, divide by 0.62; phosphate in mmol/L to mg/dl, divide by 0.323; and albumin in g/L to g/dl, divide by 10.
↵b Defined as the proportion of patients with diuresis >100 ml/24 h.
↵c In selection of patients with RKF.
↵d Mean of urea and creatinine clearance.

Table 2.

Results from univariable and multivariable linear regression analyses^a of 6-mo change in β2M in HDF patients

Determinant	Univariable Regression		Multivariable Regression
Determinant	B^b	95% CI	B	95% CI
Gender (male)	1.3	−2.0 to 4.6
Age (per 10 yr)	0.2	−0.9 to 1.3
History of cardiovascular disease	2.5	−0.7 to 5.7	1.9	−1.3 to 5.2
Diabetes mellitus	2.7	−1.0 to 6.3	1.7	−2.1 to 5.5
Dialysis vintage (per yr)	−0.4	−0.9 to 0.2
Body mass index (per kg/m²)	0.0	−0.3 to 0.3
Arteriovenous fistula	0.2	−3.5 to 3.9
Convective volume (per L/treatment)	0.1	−0.3 to 0.6	0.3	−0.2 to 0.7
Dialysis frequency (per session/wk)	−6.3	−12.7 to 0.1	−3.7	−10 to 3.0
GFR (per ml/min/1.73 m²)	0.9	0.5 to 1.4^c	0.9	0.4 to 1.5^c
Serum albumin (per g/dl)	−0.2	−0.7 to 0.2

↵a Adjusted for participating center.
↵b The regression coefficient (B) reflects the change in β2M levels between baseline and 6 mo. Positive values of B indicate smaller decreases in β2M during the study period.
↵c P < 0.001.