Study Design

Body fluid composition and plasma BNP values were measured in 158 nondialysis patients with CKD (age ≥20 years) by using a multifrequency bioelectrical impedance analysis (MFBIA) instrument (Inbody S20®; Biospace Co. Ltd., Seoul, South Korea) between October 2009 and May 2015. BNP was determined by using an enzyme-linked immunosorbent assay (TOSOH CORPORATION, Tokyo, Japan). We identified 147 patients with complete clinical data, and simultaneously assessed their age, sex, underlying disease, presence or absence of cardiac comorbidities, anthropometric measurements, blood pressure, and prescribed diuretic and antihypertensive agents. Cardiac comorbidities were defined as a composite of hospital-treated myocardial infarction or coronary intervention, hospital-treated heart failure, surgical-treated valvular disease, or medical-treated arrhythmia. The surveyed patients were categorized according to the tertile of the log-transformed plasma level of BNP, and data for the total cholesterol, triglyceride, fasting blood glucose, C-reactive protein, estimated glomerular filtration rate (eGFR), and ratio of urinary protein to creatinine in a random urine sample (UPCR) were extracted from the electronic medical records on the same day. The patients were classified as underweight, normal, overweight, or obese according to the body mass index (BMI) cutoffs of <18.5, 18.5-24.9, 25.0-29.9 and ≥30 [9]. The stage of CKD was classified based on the GFR category [1], and the eGFR was calculated according to the revised formula for Japanese patients using the Modification of Diet in Renal Disease method [10] as follows: 194 × creatinine^-1.094 × age^-0.287 (× 0.739 for women). The geriatric nutritional risk index, a simplified nutritional screening index, was calculated as follows: (14.89 + albumin [g/dl]) + (41.7 × body weight/ideal body weight of BMI 22) [11]. Treatment-resistant high blood pressure was defined as a systolic blood pressure ≥140 mm Hg or diastolic blood pressure ≥90 mm Hg in patients without proteinuria and as a systolic blood pressure ≥130 mm Hg or diastolic blood pressure ≥80 mm Hg in patients with proteinuria who received three or more hypertension medications, including diuretics. Blood pressure was considered treatment resistant if the patient took four or more drugs for control [1,12].