Nutrition Screening Adults

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NSA: Serum Proteins (2009)

Serum Proteins: Albumin and Prealbumin

Dietitians and other clinicians, administrators and surveyors (likely based on the work of Keys*) have traditionally used serum protein levels as indicators of protein status in adults. To evaluate the evidence supporting this practice, the expert workgroup reviewed more than 190 research publications to identify associations between changes in serum protein levels and weight loss and nitrogen balance. In order to avoid the well recognized influences of the inflammatory response and fluid status on serum protein levels, the workgroup limited the evidence analysis to four models of protein-energy restriction: anorexia nervosa, non-malabsorptive gastric partitioning bariatric surgery, calorie-restricted diets and starvation.

There were a number of criteria guiding the inclusion or exclusion of studies for this topic. Studies were excluded if participants suffered burns, trauma, cancer, liver disease with ascites, had unmeasured protein losses due to hemo- or peritoneal dialysis, or were in a postoperative or refeeding phase of care. In addition, studies were excluded if the period of starvation was less than five days, if intravenous albumin was administered, or if albumin measurements were from urine rather than sera. Intervention studies were only considered for inclusion if control arm of RCTs did not receive an intervention. 

Three different inclusion dates guided the literature search. Inclusion dates were chosen based on the period of time at which clinicians began widely using nitrogen balance to evaluate change in body protein, the reference year for use of the laparoscopic banding procedure and for starvation, the approximate year when the current method of measuring serum albumin began (bromcresol green method).

A large number of the studies reviewed could not be included based on the exclusion criteria. The most common reasons for exclusion included: intervention in both study arms, population or diagnosis not meeting criteria, or albumin, prealbumin or nitrogen balance not reported. Other reasons for exclusion included review article or meta-analysis (which were handsearched for references), not a starvation study or short duration of starvation or were outside of date range. For more information, see the search plan and results for albumin and prealbumin.

A total of 12 studies were accepted for inclusion to answer the following four questions on the associations between changes in serum protein levels and weight loss and nitrogen balance.

*Reference: Keys A. Caloric undernutrition and starvation, with notes on protein deficiency. J Am Med Assoc. 1948 Oct 16;138(7):500-511.