Abstract: 【Abstract】Objective To explore the best period to evaluate the nutritional status in maintenance hemodialysis (MHD) patients. Methods A total of 66 MHD patients (53 cases in the young and middle age group, and 13 cases in the older age group) were enrolled in this study. Based on the body weight gain in the interval between two sessions of dialysis, each age group was subdivided into two subgroups: patients with body weight gain > 4.5% of their dry body weight (37 cases in the young and middle age group, and 6 cases in the older age group), and those with body weight gain < 4.5% of their dry body weight (16 cases in the young and middle age group, and 7 cases in the older age group). Triceps skinfold (TSF), mid-arm circumference (MAC), and mid-arm muscle circumference (MAMC) derived from TSF and MAC were measured and compared every month before and after dialysis. Results (a) MAC, TSF and MAMC were significantly larger before dialysis than after hemodialysis (29.33±3.48cm vs. 28.78±3.40cm for MAC, t=10.091, P=0.000; 21.41±6.00mm vs. 20.57±5.92mm for TSF, t=10.590, P=0.000; 23.00±2.75cm vs. 22.52±2.47cm for MAMC, t=3.534, P=0.000) in all patients. MAC, TSF and MAMC values were significantly larger before dialysis than after dialysis in both the young and middle age subgroup and the older age subgroup; MAC value was 29.21±3.44cm vs. 28.68±3.56cm (t=8.437, P=0.000) in the young and middle age subgroup, and was 29.81±3.80cm vs. 29.19±3.69cm (t=6.009, P=0.000) in the older age subgroup; TSF value was 21.43±6.06mm vs. 20.52±5.98mm (t=9.865, P=0.000) in the young and middle age subgroup, and was 21.34±6.00mmin vs. 20.74±5.88mm (t=4.242, P=0.000) in the older age subgroup; MAMC value was 22.99±2.80cm vs. 22.50±2.47cm (t=2.953, P=0.000) in the young and middle age subgroup, and was 23.05±2.68cm vs. 22.64±2.57cm (t=5.177, P=0.000) in the older age subgroup. (b) No statistical differences were found in the influence of body weight gain on TSF, MAC and MAMC values collected before and after dialysis in the two body weight gain subgroups. Conclusion To avoid the body weight gain in the interval between two dialysis sessions, TSF, MAC and MAMC measurements should be carried out when MHD patients had no complaint of uncomfortable feelings such as muscular tension, cramps and hypotension symptoms after dialysis. These measurements provide accurate data that are helpful for long-term nutritional evaluation and management.

Key words: Body measurement, Triceps skinfold, Mid-arm circumference, Mid-arm muscle circumference