Comparison of experimental and bioelectrical impedance analysis methods in calculation of dry weight in peritoneal dialysis patients

BACKGROUND: To optimize dialysis prescription and fluid balance of the peritoneal dialysis (PD) patients, it is important to assess their dry weight accurately. The experimental evaluation is the method which is widely used in PD centers which needs continuous and controlled reduction of the postdialysis weight down to the point where patient does not show any signs of hypotension and volume overload. This study intends to indicate that the bioelectrical impedance analysis (BIA) method can be used as an alternative method to evaluate the dry weight. MATERIALS AND METHODS: The demographic data of 101 continuous ambulatory peritoneal dialysis (CAPD) patients of Alzahra and Noor hospitals of Isfahan University (50 males and 51 females) who had been referred for periodical examinations from April 2009 to April 2010 were extracted from their files. The normal body volume was selected as the inclusion criteria and identified by an examiner group (a nephrologist, a general practitioner and a PD nurse). The patients’ dry weights were calculated based on both methods. The bioelectrical impedance analysis method was done by the Maltron Bioscan ver916 and data were analyzed by SPSS program ver18. RESULTS: There were 49.5% males and 50.5% females with the mean age of 54.6±17 years. The mean dry weight in the experimental method was 63.4±13.3 kg in comparison to the other (61.5± 13.7 kg). There was a significant difference between the results (P value <0.001) depended on the gender t-test, but there was a 98% correlation between the results by two methods. No correlation observed between the patient's age, body mass index, blood pressure, previous hemodialysis history, PD duration time, and underlying disease. CONCLUSION: The study showed that there is significant difference between the two methods. However, there was 98% direct correlation between them. It is concluded that bioelectrical impedance analysis could be a better alternative for accurate evaluation of dry weight in PD patients because it is a fast and cheap method and does not depend on examiner's capability. Further studies based on the results of this method are recommended to consider this method as the gold standard.