By Mary Ellen Posthauer RDN, CD, LD, FAND
For many years clinicians have relied on serum proteins, such as albumin and pre-albumin, as markers of nutritional status. However, current research indicates that there is little data to support this practice. Albumin and pre-albumin (transthyretin) are acute phase proteins. The advent of the inflammatory process - including infection, trauma, surgery, burns, and other wounds - elicits the acute phase response. During this acute phase response, these proteins decline and are called negative acute phase reactants.
Albumin is a visceral protein and has a large body pool, distributed between the vascular and interstitial spaces. Only 5 % is synthesized daily. Albumin functions as a carrier protein, and assists in maintaining oncotic pressure. Corticosteroids, insulin, thyroid hormone, and dehydration all increase albumin levels. During inflammation, cytokines increase, especially interleukin-6, which is responsible for the production of acute phase proteins. This increased cytokine production results in albumin being pulled from the intravascular spaces and circulating to the liver until the inflammatory process resolves.
Pre-albumin, also a visceral protein, acts as a transport protein for thyroxine and as a carrier for retinal binding protein. Due to the short half-life of pre-albumin (2-3 days), it is assumed to be a better indicator of nutritional repletion. However, it is affected by the same inflammatory process as albumin and decreases during the acute phase response. A pre-albumin level declines with infection, hyperglycemia, dialysis, liver disease, and surgery. Pre-albumin may be elevated with corticosteroids and acute renal failure, as it is degraded by the kidneys.
What does research indicate?
Multiple studies, either randomized, interventional, or prospective cohort studies, fail to demonstrate a relationship between nutritional status and serum protein levels. Declining intake does not correlate with declining serum protein levels, nor does increased nutritional intake result in improved values. Low levels of albumin and pre-albumin are indicators of morbidity and mortality, and increased levels may reflect the improvement in the overall clinical status of the individual.
The focus of nutritional care should be on risk factors like unintended weight loss, undernutrition, declining food/fluid intake, and slow wound healing. Individuals with any of these risk factors will benefit from a comprehensive nutrition assessment, as well as aggressive interventions including weight monitoring and oral intake.
As a clinician, ask yourself the following questions:
- Is the individual actually receiving the nutrition care prescribed?
- Are the supplements ordered, delivered, and consumed?
- Is the feeding tube running at the ordered rate for the number of hours ordered?
Answering these questions will directly aid in providing nutrition assessments and interventions.
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Ferguson RP, O’Connor P ,Crabtree B, Batchelor A, Mitchell J, Coppola D. Serum albumin and prealbumin as predictors of hospitalized elderly nursing home residents. J Am Geriatr Soc.1993;41:545-549.
Friedman FJ, Campbell AJ, Caradoc-Davies TH. Hypoalbuminemia in the elderly is due to disease not malnutrition.Clinical Experimental Gerontol. 1985;7:191-203.
Myron Johnson A, Merlini G, Sheldon J, & Ichihara K. (2007). Clinical indications for plasma protein assays: transthyretin (prealbumin) in inflammation and malnutrition. Clinical Chemistry and Laboratory Medicine: CCLM / FESCC, 45(3), 419-426
About The Author
Mary Ellen Posthauer RDN, CD, LD, FAND is an award winning dietitian, consultant for MEP Healthcare Dietary Services, published author, and member of the Purdue University Hall of Fame, Department of Foods and Nutrition, having held positions on numerous boards and panels including the National Pressure Ulcer Panel and the American Dietetic Association’s Unintentional Weight Loss work group.
The views and opinions expressed in this blog are solely those of the author, and do not represent the views of WoundSource, Kestrel Health Information, Inc., its affiliates, or subsidiary companies.