The concentration of serum albumin s[alb] has been considered the most
powerful predictor of death in hemodialyzed patients. Because low s[alb] is
also a marker for protein-calorie malnutrition, the usual paradigm is that
malnutrition causes a decline in health status that leads to death in
hemodialyzed patients with low s[alb]. Recent studies by Kaysen et al (KI
48:510-16, Aug 1995) have challenged this concept. Comparing stable
hemodialyzed patients with normal (4.2 g/dl) versus low (3.2 g/dl) s[alb]
they showed that albumin synthetic rates were decreased in the low s[alb]
group. The low s[alb] group also had elevated levels of the acute phase
reactants alpha-2 macroglobulin and ferritin with a tendency for elevation
of C-reactive protein (CRP). Nutritional status including dietary protein
intake, protein catabolic rate, and caloric intake were the same in both
groups. Since albumin is a well-established negative acute phase reactant, a
concern was raised that all of these findings including the low s[alb] are
due to an occult inflammatory process that may predispose to death.
Several abstracts were presented at the November ASN meetings in support of
this concept. Studies reported by Bergstrom
(2218, 573) showed that CRP was
an equally if not more powerful predictor of death than s[alb] and
nutritional status in 128 hemodialyzed patients followed for 4 years. A Cox
proportional hazard model showed that s[alb] lost its significance as a
predictor of mortality when corrected for CRP. In another report from the
same institution (995,586) Qureshi and
his colleagues found a significant
negative correlation between s[alb] and CRP in the same population. CRP was
an equally powerful predictor of s[alb] as nutritional status, suggesting
that non-nutritional factors associated with the acute phase response are
responsible for the low s[alb]. Bologa et al
(996,573) showed in a
population of 94 hemodialyzed patients that predialysis levels of TNF-alpha
correlated inversely with s[alb] and cholesterol levels. During the
following year patients with relatively high TNF-alpha and IL-6 levels had
higher mortality supporting the hypothesis that inflammatory cytokines
mediate the hypoalbuminemia, hypocholesterolemia, and mortality in
hemodialyzed patients. (Thomas A. Depner)
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