Malnutrition-Inflammation Score Independently Determined Cardiovascular and Infection Risk in Peritoneal Dialysis Patients

Background: The malnutrition-inflammation score (MIS) is an indicator of malnutrition-inflammation complex syndrome and an outcome-predictor in maintenance hemodialysis (MHD) patients. However, its utility in peritoneal dialysis (PD) patients and its association with the Charlson comorbidity index (CCI) have not yet been examined. Methods: All chronic stable PD outpatients in the PD center of National Taiwan University Hospital in January 2006 were studied and followed for up to 18 months. The baseline MIS and CCI at the beginning of the study and the dates and causes of mortality or hospitalization during the study period were obtained. Results: A total of 141 PD patients were enrolled. During the study period, 8 patients died and 40 patients had major cardiovascular or infection events. The CCI correlated positively and significantly with the MIS (r = +0.344, p ! 0.001). The MIS and CCI were both independent predictors of cardiovascular and infection events in the multivariate Cox proportional Received: June 20, 2009 Accepted: November 5, 2009 Published online: June 24, 2010 Chih-Kang Chiang, MD, PhD Department of Internal Medicine National Taiwan University Hospital No. 7 Chung-Shan South Road, Taipei (Taiwan) Tel. +886 2 2312 3456, Fax +886 2 2322 3905, E-Mail ckchiang @ ntuh.gov.tw © 2010 S. Karger AG, Basel 0253–5068/10/0301–0016$26.00/0 Accessible online at: www.karger.com/bpu Malnutrition Inflammation Score in Peritoneal Dialysis Patients Blood Purif 2010;30:16–24 17 active protein, pro-inflammatory cytokines, albumin, prealbumin, body composition, and anthropometrics as indices of inflammation or nutrition status [3, 4] . Although these simple parameters can easily be assessed, they are affected by many factors other than malnutrition or inflammation. In addition, the identification of a ‘complex’ syndrome using only 1 or 2 parameters is clearly incomprehensive and can easily lead to biased results. A comprehensive and quantitative measure called the malnutrition-inflammation score (MIS) was developed by Kalantar-Zadeh et al. [6] ; it is determined on the basis of the medical history, physical examination, body mass index (BMI), and laboratory parameters of the patient. In MHD patients, the MIS is associated with 1and 5-year prospective mortality [5, 6] , and it is superior to the subjective global assessment (SGA) and other inflammatory markers in predicting 5-year mortality [5] . Our previous study also found the MIS to be a useful tool in the risk stratification of Asian hemodialysis patients [7] . However, the utility of the MIS in PD patients had rarely been examined, although some authors have found a reasonable correlation between the MIS and SGA in this population [11, 14, 15] . The Charlson comorbidity index (CCI) is a comorbidity scale that has been developed for general medical patients [8] , but its application in dialysis patient populations to predict clinical outcomes, including length of hospital stay, inpatient costs, and mortality, has also been confirmed [9, 10] . Although the CCI has been accepted as a valid predictor of outcomes in incident PD patients, its utility in prevalent PD patients has not yet been established. Several comorbidities, including hepatitis C, diabetes mellitus (DM), and cardiovascular disease, have been associated with more severe malnutrition or inflammation conditions in end-stage renal disease (ESRD) [1, 12, 13] . From this point of view, the MIS may have a strong correlation with the CCI. The primary aim of our study is to validate the use of the MIS and the CCI in prevalent PD patients. The secondary aim is to clarify the association between malnutrition, inflammation, and comorbidities in a PD population. Subjects and Methods Patients All patients who received chronic PD treatment in the PD center of the National Taiwan University Hospital in January 2006 were recruited into the study. The study protocol conformed to the ethical guidelines of our institution, and informed consent was obtained from each participant. The following patients were excluded from the study: patients who had received PD for less than 3 months, those who had received MHD for more than 3 months before initiation of PD, those who received PD due to renal graft failure, and those who had been hospitalized or had a documented acute infection in the recent 3 months. These exclusion criteria ensured that all the enrolled subjects were chronic stable PD patients. Age, gender, BMI, duration of PD, and comorbid conditions were recorded for all enrolled patients. The duration of PD was defined as the duration of time from the first day of PD treatment to January 1, 2006. The MIS and CCI of each patient was also recorded in January 2006. Data Collection All enrolled patients received standard clinical care and were followed up for 18 months until June 30, 2007. The date and cause of mortality, hospitalization, and dropout during the study period were documented for all patients. Patients were classified as having a major cardiovascular event if the major cause of death or hospitalization was acute coronary syndrome, ischemic heart disease, congestive heart failure, cardiac arrhythmia, or peripheral arterial disease. They were classified as having a major infection event if the major cause of death or hospitalization was PD-related infection, including peritonitis and exit site infection, sepsis, pneumonia, urinary tract infection, cellulitis, or any systemic or localized infection. Patients with an emergency room (ER) stay over 24 h were also classified as being hospitalized, and the causes of the ER stay were documented after chart review. All laboratory measurements were performed in the laboratories of National Taiwan University Hospital using standardized and automated methods. All blood samples were obtained in January 2006. The glomerular filtration rate (GFR) of residual renal function was calculated as the mean of 24-hour renal urea clearance and 24-hour renal creatinine clearance. The GFR within 2 months of the beginning of this study was defined as the baseline residual renal function. The weekly fractional urea clearance (Kt/V) was the sum of peritoneal Kt/V and the residual renal Kt/V, which was calculated using the urea kinetic model formula. The results of the peritoneal equilibration test (PET), which were expressed as D/D 0 glucose ratio and D/P creatinine ratio at the 4th hour, were all obtained within 6 months before or after the initiation of the study. Malnutrition-Inflammation Score and Charlson Comorbidity Index The MIS consisted of 4 main parts, the medical history, physical examination, BMI, and laboratory parameters of the patient [6] ( table 1 ). The medical history included weight changes, dietary intake, gastrointestinal symptoms, functional capacity, and presence of comorbidities. The number of years the patient was on dialysis treatment was also defined as a type of morbidity. The physical examination involved detection of loss of subcutaneous fat and signs of muscle wasting. Laboratory parameters were defined as the serum albumin and serum total iron-binding capacity (TIBC) levels. Each of the above-mentioned 10 components had 4 levels of severity ranging from 0 (normal) to 3 (severely abnormal). One of the investigators (H.-H.W.) interviewed all the patients in January 2006 to obtain information on physical morbidity and self-care ability and assessed their subcutaneous muscle tissue and muscle mass. The MIS of the patients was recorded