NKF KDOQI GUIDELINES

KDOQI Clinical Practice Guidelines for Nutrition in Chronic Renal Failure

I. ADULT GUIDELINES

A. MAINTENANCE DIALYSIS

1. Evaluation of Protein-Energy Nutritional Status

RATIONALE

The predialysis or stabilized serum cholesterol concentration may be a useful screening tool for detecting chronically inadequate protein-energy intakes. Individuals undergoing MHD who have a low-normal (less than approximately 150 to 180 mg/dL) nonfasting serum cholesterol have higher mortality than do those with higher cholesterol levels.^{14,25,47,50,55} As an indicator of protein-energy nutritional status, the serum cholesterol concentration is too insensitive and nonspecific to be used for purposes other than for nutritional screening, and MD patients with serum cholesterol concentrations less than approximately 150 to 180 mg/dL should be evaluated for nutritional deficits as well as for other comorbid conditions.

Serum cholesterol is an independent predictor of mortality in MHD patients.^14,19,47,55 The relationship between serum cholesterol and mortality has been described as either "U-shaped" or "J-shaped," with increasing risk for mortality as the serum cholesterol rises above the 200 to 300 mg/dL range¹⁴ or falls below approximately 200 mg/dL.^19,25,47,50 The mortality risk in most studies appears to increase progressively as the serum cholesterol decreases to, or below, the normal range for healthy adults (£ 200 mg/dL).^{14,19,25,50,55} Not all studies of MHD patients show that serum cholesterol levels predict mortality, however.^19,23,42 The relationship between low serum cholesterol and increased mortality is not observed in the CPD population,^{14,25,42,44,52} possibly because sample sizes in studies of individuals undergoing CPD are smaller and possibly due to confounding by greater energy (glucose intake) and/or hypertriglyceridemia. In one study, higher serum cholesterol concentrations (> 250 mg/dL) were associated with increased mortality in CPD patients.⁵⁶

Predialysis serum cholesterol is generally reported to exhibit a high degree of collinearity with other nutritional markers such as albumin,⁴² prealbumin,⁴² and creatinine,⁴⁴ as well as age.⁴⁴ In MHD patients, the predialysis serum cholesterol level measured may be affected by non-nutritional factors. Cholesterol may be influenced by the same comorbid conditions, such as inflammation, that affect other nutritional markers (eg, serum albumin).⁴² In one study there was no difference in serum cholesterol in CAPD patients whose serum albumin level was less than 3.5 g/dL as compared with those with levels ³ 3.5 g/dL.³³

RECOMMENDATIONS FOR RESEARCH

What are the conditions under which serum cholesterol is a reliable marker of protein-energy nutrition? What can be done to increase the sensitivity and specificity of the serum cholesterol as an indicator of protein-energy nutritional status?
The relationships between other markers of protein-energy nutritional status (eg, serum albumin or anthropometry) and serum cholesterol are limited, somewhat contradictory, and need to be better defined.
How does nutritional intervention in malnourished MD patients affect their serum cholesterol concentrations?
Recent data suggest that serum cholesterol exhibits a negative acute-phase response to inflammation.⁴² The relationship among serum cholesterol, nutritional status, and inflammation needs to be further investigated.
Why does mortality increase when the serum cholesterol falls outside the 200 to 250 mg/dL range?
More information is needed about the patterns of morbidity and mortality associated with abnormal serum cholesterol concentrations in MD patients. For example, in these individuals, is cardiovascular mortality directly related to the serum cholesterol level and are malnutrition and mortality from infection inversely related to the serum cholesterol level?
Additional data investigating the relationships among serum cholesterol, protein-energy nutritional status, morbidity, and mortality are needed for persons undergoing CPD.