Research Blog

December 7, 2022

Protein Biomarkers: Albumin

Optimal Takeaways

Albumin is a vital protein that acts as a carrier for nutrients, hormones, enzymes, and medications. It has anti-inflammatory, anti-coagulant, and antioxidant effects and also maintains the oncotic pressure that helps stop the fluid in blood vessels from leaking out into tissues. 

Albumin levels may decrease due to liver disease, inflammation, infection, surgery, oxidative stress, ischemia, heart disease, stroke, fluid overload, advanced malnutrition, diabetes, and advanced kidney disease. Optimal levels are associated with a reduction in surgical complications, short-term and long-term survival in hospitalized patients, and reduced mortality in healthy adults. High levels may be associated with dehydration.

Conventional Lab Range: 3.60 - 5.10 g/dL (36.00 g/L)

Optimal Dx’s Optimal Range: 4.50 – 5.00 g/dL (45.00 – 50.00 g/L)  

Low albumin is associated with liver disease, kidney disease, diabetes, cardiovascular disease, infection, inflammation, oxidative stress, ischemia, advanced malnutrition, fluid overload (Arques 2018), tissue necrosis, burns, surgery, stress, and myocardial infarction (Pagana 2021). Hypoalbuminemia is considered a prognostic factor for MI, stroke, and heart failure (Alsancak 2018).

High albumin levels may indicate dehydration so hydration status must be assessed if levels are above optimal.

Overview

Albumin is produced in the liver and is the most abundant protein in the blood. It accounts for ~60% of the protein in circulation and is part of the total protein measurement along with globulin. Albumin is a major carrier of hormones, enzymes, nutrients, and drugs, and is instrumental in the maintenance of the colloidal osmotic or “oncotic” pressure that prevents fluid from leaking out of blood vessels and into interstitial spaces (Pagana 2021). Very low albumin levels can lead to edema or even anasarca, which is severe generalized edema.

Albumin acts as “protein storage” in that it can be catabolized to release amino acids that are then used for protein synthesis and energy generation. This catabolism also releases nutrients such as zinc that are transported by albumin (Malavolta 2015).

Assessment of albumin can be complex as synthesis decreases with impaired liver function but also decreases acutely with inflammation, infection, burns and surgery. Levels can also decrease with oxidative stress, ischemia, heart disease, stroke, fluid overload, advanced malnutrition, diabetes, and advanced kidney disease. A reduction in albumin will ultimately compromise its valuable antioxidant, anti-inflammatory, and anticoagulant effects (Arques 2018).

Inflammation, especially systemic inflammation, can reduce albumin synthesis as well as increase its degradation and leakage into intercellular spaces. Albumin can also be lost into the urine with kidney disorders and into the gastrointestinal tract with protein-losing enteropathies. Declining albumin coupled with unexplained weight loss may reflect advancing cancer and should be further investigated (Keller 2019).

Albumin is considered a potent antioxidant and accounts for 70% of the free-radical trapping ability of serum. It is able to bind oxidative metal ions including copper, iron, nickel, vanadium, and cobalt. Excessive oxidative stress or ischemia can damage albumin and interfere with its vital functions. Ischemia-modified albumin can be measured and is approved as an early diagnostic biomarker in myocardial infarction (Sitar 2013). Albumin inhibits the activation and aggregation of platelets as well as endothelial cell apoptosis (Alsancak 2018).

Albumin at the low end of the conventional lab range is associated with increased risk of surgical complications and increased mortality (Bendersky 2017). Earlier meta-analysis of 8 studies found a significant increase in coronary heart disease risk with an albumin of 3.8 versus 4.2 g/dL (Danesh 1998). Low albumin in elderly subjects is associated with increased sepsis and mortality following surgery for hip fracture (Keller 2019).

Albumin above 4.5 g/dL has been associated with greatest short-term and long-term survival in hospitalized patients (Akirov 2017). Maintaining albumin above 4.5 g/dL was associated with a reduction in all-cause mortality in healthy adults and can be considered an optimal goal (Fulks 2010). Albumin may appear falsely elevated in dehydration so hydration status must be considered during clinical assessment.

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References

Akirov, Amit et al. “Low Albumin Levels Are Associated with Mortality Risk in Hospitalized Patients.” The American journal of medicine vol. 130,12 (2017): 1465.e11-1465.e19. doi:10.1016/j.amjmed.2017.07.020

Alsancak, Yakup, et al. "Role of calcium–albumin ratio in severity of coronary artery disease assessed by angiographic SYNTAX score." Archives of Clinical and Experimental Medicine 3.3 (2018): 174-178.

Arques, Stephane. “Human serum albumin in cardiovascular diseases.” European journal of internal medicine vol. 52 (2018): 8-12. doi:10.1016/j.ejim.2018.04.014

Bendersky, Victoria et al. “Determining the Optimal Quantitative Threshold for Preoperative Albumin Level Before Elective Colorectal Surgery.” Journal of gastrointestinal surgery : official journal of the Society for Surgery of the Alimentary Tract vol. 21,4 (2017): 692-699. doi:10.1007/s11605-017-3370-9

Danesh, J et al. “Association of fibrinogen, C-reactive protein, albumin, or leukocyte count with coronary heart disease: meta-analyses of prospective studies.” JAMA vol. 279,18 (1998): 1477-82. doi:10.1001/jama.279.18.1477

Fulks M, Stout RL, Dolan VF. Albumin and all‐cause mortality risk in insurance applicants. J Insur Med. 2010;42: 11–17.

Keller, Ulrich. “Nutritional Laboratory Markers in Malnutrition.” Journal of clinical medicine vol. 8,6 775. 31 May. 2019, doi:10.3390/jcm8060775

Malavolta, Marco et al. “Serum copper to zinc ratio: Relationship with aging and health status.” Mechanisms of ageing and development vol. 151 (2015): 93-100. doi:10.1016/j.mad.2015.01.004

Noh, Eul et al. “The clinical role of serum albumin in Organophospate poisoning.” Basic & clinical pharmacology & toxicology vol. 128,4 (2021): 605-614. doi:10.1111/bcpt.13546

Pagana, Kathleen Deska, et al. Mosby's Diagnostic and Laboratory Test Reference. 15th ed., Mosby, 2021.

Sitar, Mustafa Erinç et al. “Human serum albumin and its relation with oxidative stress.” Clinical laboratory vol. 59,9-10 (2013): 945-52

Tag(s): Biomarkers

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