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Abstract
Carbamylation requires isocyanic acid derived from urea. Carbamylation of hemoglobin
(Hb) produces carbamylated Hb (carbHb), which could serve as a marker of posttranslational
protein modification possibly associated with such uremic complications as atherosclerosis.
Since relative carbHb levels are determined by mean urea concentration and duration
of exposure, they could be used to assess the adequacy of a patient’s hemodialysis
(HD) regimen. We therefore determined the relationship between carbHb and urea kinetics
in patients with chronic renal failure (CRF) undergoing maintenance HD. In pre-HD
determinations as well as in nondialyzed subjects including healthy subjects and CRF
patients without dialysis, carbHb correlated well with blood urea nitrogen (BUN) concentrations,
especially with BUN averaged for the preceding 1–3 months. In HD patients, carbHb
correlated significantly with urea kinetics (time-averaged concentration of urea,
or TAC<sub>urea</sub>, K<sub>t</sub>/V and urea reduction rate). The estimated mean
urea concentration in HD patients calculated from the relationship between carbHb
and averaged BUN over 3 months in the nondialyzed groups was lower than TAC<sub>urea</sub>,
suggesting that TAC<sub>urea</sub> may be an overestimate. Pre-HD BUN is not a good
nutritional index since detrimental decreases in urea elimination from the body can
elevate pre-HD BUN independently of nutrition. We therefore devised a new nutritional
index, BUN/carbHb, which correlated significantly with serum albumin as well as the
normalized protein catabolic rate. These results demonstrate that carbHb accurately
reflects uremic control and the BUN/carbHb ratio could serve as an index of nutritional
state in HD patients.