Use of Serum Albumin and Prealbumin in Determining Nutritional Status

We continue to receive questions from practitioners regarding whether it is appropriate to use serum albumin and/or prealbumin to determine nutritional status and/or nutritional repletion. To answer this question, I'll share some information from our book, The Complete Guide to Nutrition Care for Pressure Ulcers: Prevention and Treatment, Copyright 2012:

Laboratory Assessment: Biochemical data analysis may help clinicians to evaluate overall health issues however, care must be taken in the interpretation of lab values for use as nutritional markers. Although markers of protein status such as albumin and prealbumin may assist the clinician to establish progress, they may not correlate with clinical observations of nutritional status (1-3). Since it is impossible to separate nutrition from total health status, these lab values are more useful in helping to establish overall prognosis and severity of illness.

Only 3% of the body's total protein is in the plasma and extravascular fluids. About 10% is visceral organ protein. Because plasma protein measurements are quick and inexpensive, and because many plasma proteins are synthesized in the liver, plasma protein has historically been used to assess protein status. Neither serum albumin or prealbumin are accurate markers of protein or nutritional status.

Albumin has a long half life of about 20 days so the concentration in the blood changes slowly. There is a large extravascular pool of albumin that can be available to return to the circulation when needed, thus skewing the results of lab tests. There are also many factors which can decrease albumin levels due to inflammatory cytokine production or other comorbidity even when a person's protein intake is adequate: infection, acute stress, surgery or cortisone excess (4). Dehydration may falsely elevate albumin levels.

Prealbumin (transthyretin and thyroxine-binding albumin) has a half life of only 2-3 days, so practitioners have historically assumed that it is a better indicator of protein status. However, prealbumin is subject to the same factors that make albumin a poor nutritional indicator. Inflammatory stress, metabolic stress and zinc deficiency decrease prealbumin levels. In addition, prealbumin levels may also be maintained during malnutrition (5,6).

CMS further clarifies in F314 Pressure Sores of the CMS State Operations Manual, Surveyor Guidance: Although some laboratory tests may help clinicians evaluate nutritional issues in a resident with pressure ulcers, no laboratory test is specific or sensitive enough to warrant serial/repeated testing. Serum albumin, pre-albumin and cholesterol may be useful to help establish overall prognosis; however, they may not correlate well with clinical observation of nutritional status (1,2). At his or her discretion, a practitioner may order test(s) that provide useful additional information or help with management of treatable conditions (7).

References

1. Covinsky KE, Covinsky MH, Palmer RM, Sehgal AR. Serum albumin concentration and clinical assessments of nutritional status in hospitalized older people: different sides of different coins? J Am Geriatr Soc. 2002;50:631-637.

2. 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.

3. 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.

4. Friedman FJ, Campbell AJ, Caradoc-Davies TH. Hypoalbuminemia in the elderly is due to disease not malnutrition. Clinical Experimental Gerontol. 1985;7:191-203.

5. Mahan K and Escott-Stump S, Krause's Food and Nutrition Therapy, 12thed, 2008. Saunders, Philadelphia, PA.

6. Thomas DR. Prevention and Treatment of Pressure Ulcers. J Am Dir Assoc 2006;7:46-59.

7. Centers for Medicare & Medicaid Services. Department of Health and Human Services. State Operations Manual, Guidance to Surveyors for Long Term Care Facilities, Appendix PP. Rev. 70. 01-07-11. Accessed December 11, 2013.