Subjects
All eligible HD and PD patients of Ewha Womans University Mokdong Hospital, who voluntarily participated with written informed consent, were enrolled between December 2016 and May 2017. The number of original patient cohort was 93 patients for HD group and 67 patients for PD group. Included were outpatients who had been undergoing dialysis treatment for at least 3 months and agreed to participate in this study voluntarily. We excluded patients who were younger than 18 years of age, had a plan for renal transplantation within 3 months, had a life expectancy of less than 3 months, had distinct edema observed by the investigators, acute disease phase leading to admission, hybrid dialysis type using both of hemodialysis and peritoneal dialysis, and cognitive impairments who are unable to complete questionnaires. The study was performed in accordance with the Declaration of Helsinki and was approved by the Institutional Review Board of Ewha Womans University Medical Center (EUMC 2016-09-039-001).
Data Collection
Demographic and clinical data were recorded at the time of the study by a self-report survey and included sex, age, duration of dialysis, comorbidities, marital status, work status, family support, smoking, alcohol, and medication (including anti-hypertensive agents, phosphate binders, and supplemental iron). Patients with medications that were maintained for at least 2 months before enrollment were marked as having maintenance medication.
Decreased physical activity plays an important role in etiology of PEW, so we analyzed body mass index (BMI), mid-arm circumference (MAC), and hand grip strength (HGS). HGS was measured in the hand without vascular access for HD patients after hemodialysis and in the dominant hand for PD patients. Among HD patients, 24 patients of HD had arteriovenous fistula, and 8 patients (20%) had arteriovenous graft. HGS was measured using a digital hand dynamometer (Digital grip strength dynamometer, T.K.K 5401, Takei Scientific Instruments Co., Ltd., Tokyo, Japan).
Nutritional status was determined using the 7-point subjective global assessment (SGA), scale consisting of two categories: medical history and physical examination. The medical history section included weight change, dietary intake, gastrointestinal symptoms, functional capacity, and disease and comorbidity data. The physical examination section included loss of subcutaneous fat, muscle wasting, and edema. The trained investigators rated each item from 1 to 7 and decided the overall SGA score. Based on the overall SGA score, the patients were categorized into three groups: well nourished (normal) = SGA score of 6–7, mildly to moderately malnourished = SGA score of 3–5, or severely malnourished = SGA score of 1–2[12].
In Republic of Korea, insurance-covered nutritional education programs are available for CKD patients: at initial diagnosis; and when dialysis is started. However, the program is not mandatory, and the patients are not aware of the program. Through a questionnaire, Presence of diet education prior to dialysis initiation was also recorded.
Dietary Behaviors
A questionnaire consisting of 10 items on the patient’s appropriate or inappropriate dietary behaviors was used, which was a modified version of a questionnaire for dialysis patients from a previous study [12]. The questionnaire responses were divided into three categories according to the fulfillment frequency on each question: 0 to 2 days, 3 to 5 days, or 6 to 7 days during the week. For questions in which the number of days of appropriate diet activity for health was asked, we gave the scores 0, 1, and 2 for each response in order. In contrast, for questions in which the number of days of inappropriate diet activity for health was asked, we gave the scores 2, 1, and 0 for each response in order. Therefore, higher values represented better dietary behavior. The survey was conducted twice with an interval of more than 1 week, and the average values of the survey were used.
SEMI- FFQ
The Semi-FFQ is the most commonly used questionnaire in epidemiological studies to assess long-term nutritional exposure [13]. The FFQ examines the intake frequency during a standard period as well as the amount of the listed food categories. Recently, the Semi-FFQ has been used for the assessment of nutritional intake in dialysis patients [14]. We designed the semi-FFQ for Korean dialysis patient and reported that this questionnaire would be a reliable tool for the assessment of the HD patients’ nutrient intake along with the 7-day dietary record [15]. The correlation coefficients were higher for foods consumed daily, such as steamed rice, meat and chicken, bean, egg, milk, coffee and alcohol, while those were lower in foods eaten rarely. A Semi-FFQ including 47 food items which is reflected dialysis patients’ diet was presented (Table S1), and the food items listed in the questionnaire were based on the Korean Health and Nutrition Survey. The Semi-FFQ consisted of groups of grains (rice, bread, and rice cake), meat, fish, beans, eggs, potatoes, dairy products, vegetables, and fruits classified as having low, medium, and high potassium content. The survey was conducted twice with an interval of more than 1 week, and the mean values were used.
Laboratory Parameters
The results of the most recent blood test within 1 month from the time of the survey were collected retrospectively. Blood samples were taken mid-week before the HD session for HD patients and on the outpatient visit day for PD patients. We measured the concentrations of serum albumin, blood urea nitrogen (BUN), creatinine, hemoglobin, hematocrit, sodium, phosphorus, calcium, potassium, and serum glucose.
Statistical Analysis
The results of the food intake amount and the frequency were analyzed by applying the nutrient evaluation program CAN-Pro 4.0. We analyzed the intake amounts for 20 nutrients, using the ninth revision of the National Standard Food Composition Table published by the Rural Development Administration in Korea [16]. In addition, the intake of each nutrient was compared to the recommended nutrient reference value [17].
The general characteristics, dietary behaviors, laboratory parameters, and Semi-FFQ scores of the subjects were presented as mean and standard deviation or N (%), and p-value < 0.05 was considered significant. For the comparison of the characteristics of the HD and PD groups, Student’s t-test and the chi-square test were used. Statistical analyses were conducted using the SPSS statistical package for Windows Ver. 23.0 (SPSS, Inc., Chicago, IL, USA).