The demographics of all the included patients were listed in Table 1. There were 117 MHD patients and 167 CAPD patients, with a mean age of 59.8 ± 13.8 years and a mean dialysis vintage of 41.8 ± 37.2 months (median 32, range 1–233).
The primary causes of end stage of renal disease (ESRD) were chronic glomerulonephritis (n = 93), diabetic nephropathy (n = 57), interstitial nephropathy (n = 45), hypertensive nephrosclerosis (n = 33), polycystic disease (n = 10), lupus nephropathy (n = 2), chronic pyelonephritis (n = 1), and others (n = 43).
Compared with CAPD patients, MHD patients had lower prealbumin, lower serum bicarbonate, higher albumin, higher systolic blood pressure and longer dialysis vintage. No statistical significance was found in age, gender and body mass index between CAPD and MHD patients.
Distribution of Plasma Vitamin C
Patients showed a widely distribution of plasma vitamin C levels. The median plasma level was 3.34 ug/ml and the range from the 25th to the 75th percentile [inter quartile range (IQR)] was 1.87–5.74 ug/ml. vitamin C deficiency was present in 95(33.45%) and insufficiency in 88 ( 30.99%) of the dialysis patients. 73(25.70%) patients had plasma vitamin C levels within normal range and 28(9.86%) at higher than normal levels. There were 48 patients taking vitamin C supplements (median 100 mg/day, range 50–600 mg/day), among whom, 9 patients with daily vitamin C supplement 50 to 100 mg had plasma vitamin C level less than 4 ug/ml, and 26 patients with daily vitamin C supplement 300 mg or more had higher plasma vitamin C level than normal.
Association of Vitamin C and Prealbumin, Albumin, hsCRP
In the total dialysis patients, plasma vitamin C level was positively associated with prealbumin (Spearman r = 0.268, P < 0.001), albumin (Spearman r = 0.161, P = 0.007), and inversely associated with hsCRP (Spearman r = -0.201, P = 0.001), age (Spearman r = -0.233, P = 0.000). Prealbumin is negatively correlated with hsCRP (Spearman r = -0.331, P < 0.01). No significant association was found between vitamin C and each of gender, hemoglobin, KT/V, body mass index, ferritin, or dialysis vintage in our study.
In MHD group, compared with group A, groups B and C had significantly lower age, higher albumin, higher prealbumin, and lower hsCRP (Table 2) while gender, body mass index, KT/V and dialysis vintage were comparable among the three subgroups (Table 2). The similar trend was found in CAPD patients (Table 2).
Patients receiving HDF treatment had lower log10hsCRP value(0.04 ± 0.71) compared with patients receiving HD treatment(0.52 ± 0.64, P = 0.03). There was no statistical significance in each of plasma vitamin C level, albumin and prealbumin among three MHD modalities.
Compared with patients without oral vitamin C supplements, patients with vitamin C supplements had increased albumin(38.47 ± 3.28 g/L vs 37.00 ± 4.44 g/L, P = 0.04), not significantly high prealbumin (341.08 ± 65.39 mg/L vs 336.83 ± 101.74 mg/L, P = 0.79), and not significantly low log10hsCRP(0.28 ± 0.65 vs 0.41 ± 0.69, P = 0.21).
Multivariate Analysis for Vitamin C Effects on Prealbumin and hsCRP Levels
In the whole dialysis patients, after adjusting for gender, age, diabetes and modality of dialysis, systolic blood pressure, metabolic acidosis and use of statins, per category increase of vitamin C caused 0.098 ± 0.049 decrement of log10 (hsCRP), this corresponding to 1.25 (1.12, 1.40) mg/L decrement of hsCRP (P = 0.048), (Table 3).
Plasma vitamin C was positively with prealbumin levels (P = 0.002) adjusted for hsCRP and above cofactors, prealbumin level was 58.49 ± 12.29 mg/L lower in patients with vitamin C deficiency compared with patients with normal vitamin C level.
However, there was no statistical significant association between plasma vitamin C and albumin (Table 3).
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Cite this: Low Levels of Vitamin C in Dialysis Patients is Associated With Decreased Prealbumin and Increased C-reactive Protein - Medscape - May 01, 2011.