METHODS: This multicenter, parallel, open-label, randomized controlled trial investigated the clinical efficacy of WPS in 126 malnourished CAPD patients with serum albumin <40 g/L and body mass index (BMI) <24 kg/m2. Patients randomized to the intervention group (IG, n = 65) received protein powder (27.4 g) for 6 months plus dietary counseling (DC) while the control group (CG, n = 61) received DC only. Anthropometry, biochemistry, malnutrition-inflammation-score (MIS), dietary intake inclusive of dialysate calories, handgrip strength (HGS) and quality of life (QOL) were assessed at baseline and 6 months. Clinical outcomes were assessed by effect size (Cohen's d) comparisons within and between groups.

RESULTS: Seventy-four patients (n = 37 per group) completed the study. Significantly more IG patients (59.5%) achieved dietary protein intake (DPI) adequacy of 1.2 g/kg per ideal body weight (p  0.05). A higher DPI paralleled significant increases in serum urea (mean Δ: IG = +2.39 ± 4.36 mmol/L, p = 0.002, d = 0.57 vs CG = -0.39 ± 4.59 mmol/L, p > 0.05, d = 0.07) and normalized protein catabolic rate, nPCR (mean Δ: IG = +0.11 ± 0.14 g/kg/day, p  0.05, d = 0.09) for IG compared to CG patients. Although not significant, comparison for changes in post-dialysis weight (mean Δ: +0.64 ± 1.16 kg vs +0.02 ± 1.36 kg, p = 0.076, d = 0.58) and mid-arm circumference (mean Δ: +0.29 ± 0.93 cm vs -0.12 ± 0.71 cm, p = 0.079, d = 0.24) indicated trends favoring IG vs CG. Other parameters remained unaffected by treatment comparisons. CG patients had a significant decline in QOL physical component (mean Δ = -6.62 ± 16.63, p = 0.020, d = 0.47). Using changes in nPCR level as a marker of WPS intake within IG, 'positive responders' achieved significant improvement in weight, BMI, skinfold measures and serum urea (all p  0.05).