At current study we found that there was a statistically significant correlation between CAR, CRP and albumin and MIS (r = 0.413 p = 0.026, r = 0.388 p = 0.038 and r=-0.511 p = 0.005 respectively). ANOVA showed that was a statistically significant independent correlation between MIS, CRP, albumin and CAR (for CRP p = 0.003, for albumin p = 0.008, for CAR p = 0.003). Lower albumin values, higher CRP and CAR values were found strong indicators for malnutrition in HD patients.
Malnutrition is an important phenomenon in HD patients which is responsible for adverse outcomes. Quality of life impairment, infection risk, progressive loss of body muscle and fat mass and mortality are associated with malnutrition (2,3,11). The etiology of malnutrition in ESRD is multifactorial, comprised by declining appetite, impairment of glucose and amino acid transport and metabolism, low diet quality, uremia, cytokine production, comorbidities and the dialysis procedure itself (3).
Low grade chronic systemic inflammation in which CKD patients are characterized by, is also a potential contributor to malnutrition development and progression. In HD patients, the development of inflammation is caused by various factors, including oxidative stress, uremic milieu, increased cytokine production and decrease of clearance of cytokines, dialysis procedure and infection frequency (4,12). The coexistence of malnutrition and inflammation suggests the potential relationship between these two aspects of ESRD, However the precise role of inflammation in the physiopathology of malnutrition and PEW is not totally elucidated (13). There several hypotheses regarding role of inflammation at malnutrition development in ESRD. Cytokine production affects the regulation of appetite resulting anorexia (14). Inflammation may enhance insulin resistance and impair glucose and amino acid transport metabolism (3). Resting energy expenditure is reported to be raised because of inflammatory status, contributing to muscle mass loss (13). Anabolic hormone resistance caused by inflammation also prompts catabolism (15).
While there are studies to show the relationship between SGA and inflammatory markers such as CRP, adinopectine, IL-6 in HD patients (16–18), studies about the association between MIS and CAR in HD patients are lacking. Our study is the first study in the literature to show an independent association between CAR and MIS in HD patients.
Association between CRP, albumin and MIS in CKD has been reported by number of studies. Aggarwal et al. has found an association between MIS and inflammatory markers CRP and albumin, negative correlation for albumin (p < 0.01) and positive correlation for CRP (p < 0.01) in CKD stage 3 to 5 (19). At a study conducted at pre-dialysis CKD patients, it has been reported that patients with MIS ≥ 7 had significant increase in Hs-CRP levels (p < 0.001), albumin was negative correlated with MIS in the same research (20).
Considering the studies on the HD patient group, Ashabi et al. has found positive correlation between serum CRP and MIS (p < 0.01) and negative correlation between albumin and MIS (p < 0.01) (21). Another study has reported that CRP level (β = 3.33, P < 0.001), and albumin level (β = −1.95, P = 0.008) were factors independently associated with MIS at HD patients (22) Martins et al. has found that higher CRP (OR 1.01 p < 0,001) were independently associated with a higher risk of MIS > 5 (23). Similar results have been reported by another study, CRP levels had an association with MIS (B = -0.56; P = 0.0001) (24). In our study we found that CRP and CAR are positive correlated and alb is negative correlated with MIS in HD patients.
Literature also comprises conflicting results regarding relation of MIS, CRP and albumin in HD patients. Pisetkul et al. did not found a correlation between hs-CRP and MIS at hemodialysis patients ( r = 0.08, p 0.44) (25). Different study has reported that albumin was not significantly correlated statistically with MIS in HD patients. (-0.189 p = 0.345) (26). At the research of Ekremzadeh et al, albumin was not statistically significant between two MIS groups ≥ 10 and < 10, in HD patients (15). Another study conducted in HD patients has found that while albumin level was lower when MIS ≥ 8 (p < 0.001), CRP levels did not differ between two MIS groups (27).
CAR is a novel inflammation index that has been emerged in recent years and it has been reported recently that it can better reflect the inflammation status compared to other markers (28). In current study, multiregression analysis showed that CRP, CAR, ALB were independently associated with MIS. Our research demonstrates statistically significant independent positive correlation between CAR and MIS, CRP and MIS and negative correlation between MIS and albumin. Interesting feature of our study is this is the first time in the literature that shows a strong relation between CAR and MIS in HD patients. Our findings indicate that CAR can be reliable and practical measurement for assessing nutritional status of HD patients.
Precise nutritional status assessment and to be able to detect PEW before related complications emerge are two crucial aims for management of malnutrition in maintenance HD patients. CAR can be used as valuable tool for predicting and screening of PEW and malnutrition risk in HD patients.
Sample size was a possible limitiation in our research. More studies with wider sample size are needed for this topic. At present study, we investigated the relationship between MIS and inflammation markers CAR, CRP, albumin and other biochemistry parameters at HD patients. Interesting feature of our research is that our study showed first time in the literature that CAR is independently associated with MIS in HD patients.