Welcome to part four of our look into the world of special protein testing in a clinical laboratory setting.
Over the past 2 weeks we have been posting excerpts from an article written by Bob Janetschek, MS, MT (ASCP), our Immunologicals Business Manager for the USA East Coast and Canadian territories.
Join us as we conclude our overview of the proteins most commonly considered in clinical testing.
Lipoprotein(a): Lipoprotein(a), also called Lp(a) or LPA, is a lipoprotein subclass. Lp(a) determinations are intended for use in conjunction with clinical evaluation, patient risk assessment and other lipid tests to evaluate disorders of lipid metabolism, and to assess coronary heart disease in specific populations.
Genetic studies and numerous epidemiologic studies have identified Lp(a) as a risk factor for atherosclerotic diseases, such as coronary heart disease and stroke.
Microalbumin: When kidneys are functioning normally, there is very little or no albumin in the urine. Abnormal amounts of albumin, or microalbumin, leak into the urine if kidneys are damaged. As such, microalbumin levels can aid in the diagnosis of renal disease. Early detection and treatment are important in preventing renal failure in insulin-dependent diabetics, as elevated urinary albumin is a good indicator of glomerular damage. Additionally, microalbumin levels can be a potential marker for future cardiovascular problems, including hypertension, in noninsulin-dependent-diabetes patients.
Prealbumin: Primarily synthesized in the liver, but also by the choroid plexus, prealbumin helps assess nutritional status. It has a high affinity for, and binds with, thyroxine (T4) and retinol-binding protein. Plasma concentrations are dependent on protein and energy intake, with reduced levels associated with malnutrition.
Rheumatoid factor: Rheumatoid factor (RF) is a heterogeneous group of high-molecular- weight autoantibodies directed against the body’s own immunoglobulins. They are produced by plasma cells present at sites of tissue injury. The initiating antigen is thought to be one or more viruses, or viral antigens, that persist in the joint tissues. Research has shown that environmental and genetic factors can affect the production of RF. Rheumatoid factor has also been observed in the sera of patients with lupus erythematosus, hepatitis, liver cirrhosis, syphilis and various other conditions, but the titer is much lower than that seen in rheumatoid arthritis. This abnormal protein is found in the blood and joint fluid of 60–80% of patients with active rheumatoid arthritis.
Transferrin: Transferrin principally occurs in sera, but is found at lower concentrations in other bodily fluids as well. Its main function is the transport of iron to cells. Measurement of transferrin levels aids in the diagnosis of malnutrition, acute inflammation, chronic infection, hepatic disease and iron-deficiency anemia.
Much research in medical diagnostics, genomics, life sciences and drug discovery focuses on protein chemistry because it has the widest diagnostic potential. Current studies are targeting the diagnosis, monitoring and treatment of cardiovascular disease; spinal injury and neurological disorders (including Alzheimer’s); organ transplant and rejection; new biomarkers for certain cancers; obesity and nutrition; diabetes; and autoimmune conditions (see Figure 2). Successes in medical technology hold promise for new and improved diagnostic tests for many disease indications, and the discovery of novel special protein biomarkers.
We have a catalogue of antibodies to human serum proteins, including many of those mentioned throughout this article.
1. Bakerman, S.; Bakerman, P. et al. Bakerman’s ABC’s of Interpretive Laboratory
Data, 3rd Ed. Interpretive Laboratory Data, Inc.: Valley Stream,
2. Tietz, N.W. Tietz Fundamentals of Clinical Chemistry, 2nd Ed. WB Saunders:
Philadelphia, Penn., 1982.
3. Pesce, A.J. and Kaplan, L.A. Methods in Clinical Chemistry. CV Mosby:
Maryland Heights, Mo., 1987.
4. Davidsohn, I. and Henry, J. Todd-Sanford Clinical Diagnosis by Laboratory
Methods,15th Ed. WB Saunders: Philadelphia, Penn., 1974.
Excerpt taken from the article "Special Protein Testing in the Clinical Laboratory: Overview of Available Assays" published in American Laboratory magazine, August 2016.
Reference link: http://www.americanlaboratory.com/