Dr. Ron’s Research Review – January 16, 2013

This week’s research review focuses on interpretation of lab values.

Despite the speed and simplicity of assays performance on automatic immunochemistry platforms, the interpretation of final results requires a deep knowledge of method fallibility. It is important for clinicians to know and to understand the limitation and fallibility of immunochemical methods in order to protect the patient from misdiagnosis.  (Sztefko and Szybowska 2012)

What is being measured by the immunoassay?

How accurate are low and high concentrations of the hormone/tumor marker being measured?

How do binding proteins affect hormone measurement?

How do autoantibodies, heterophilic, and anti-animal antibodies interfere with hormone/tumor markers measurement?

The article begins with a discussion of the effects of aging on lab values.

The function of endocrine glands function declines progressively with age. DHEAS concentration is about 10–20% of maximum in patients at the age of 70–80 years. The activity of the growth hormone/IGF axis also declines steadily, and a sudden cessation of the function of some elements of the hormonal system is well documented. In an elderly population, the presence of autoantibodies due to autoimmune or chronic diseases is more frequent than it is in the younger population. Changes in the serum level of specific and nonspecific hormone-binding protein, especially albumin, frequently observed in geriatric population, greatly influence the measurement of free hormones.

An older article compared lab values in three age groups. (Tietz, Shuey et al. 1992)

Dr. Ron


Articles

Interpretation of hormone levels in older patients: points for consideration

            (Sztefko and Szybowska 2012) Download

Blood hormone and tumor marker concentrations are usually determined by immunochemical methods which are based on an unique reaction between antigen and assay capture antibody. Despite the speed and simplicity of assays performance on automatic immunochemistry platforms, the interpretation of final results requires a deep knowledge of method fallibility. General lack of immunoassays standardization, presence of cross-reacting substances in patient's sample, limitation of free hormones measurement due to abnormal analyte binding protein concentrations, assay interferences due to patient's autoantibodies, and heterophilic antibodies, as well as proper interpretation of very low- and very high-sample analyte levels, are the main points discussed in respect to hormones and tumor markers measurement in geriatric population.

Laboratory values in fit aging individuals--sexagenarians through centenarians

            (Tietz, Shuey et al. 1992) Download

We determined approximately 15,000 laboratory values in 236 individuals between the ages of 60 and 90 y, 22 individuals between 90 and 99 y, and 69 individuals greater than or equal to 100 y, and compared these with values in young adults. We tested 47 different analytes in the 60-90-y group and 93 analytes in the greater than or equal to 90-y group. Na, K, Cl, and CO2 values were either identical or showed minimal change with age; pH decreased slightly. Differences in Ca values were only minor, but ionized Ca increased slightly. Phosphate decreased in men, but changed only minimally in women; parathyroid hormone increased with age. Increases with age were also observed for glucose, insulin, and C-peptide. Among the enzymes, alkaline phosphatase increased in women, but in men only greater than 90 y; gamma-glutamyltransferase increased in both sexes. Creatine kinase (CK) decreased slightly in individuals greater than 70 y and markedly in those greater than 90 y of age, whereas CK-MB decreased markedly greater than 70 y, reaching the detection limit in individuals greater than 90 y. Lactate dehydrogenase isoenzyme 5 decreased slightly with age. Urea nitrogen increased gradually with age, but creatinine increased only in individuals greater than or equal to 90 y. The increase in urea is not paralleled by a loss of protein in urine, suggesting that the possible cause of azotemia may not always be renal pathology. Urate increased in women but not in men. Liver function, as measured by total bilirubin and liver enzymes, was exceedingly well maintained. Concentrations of most proteins show little change, except for slight decreases in prealbumin, albumin, and transferrin, proteins used as an index of nutritional status. IgA values increased, IgG ranges were wider, IgM and IgD decreased, and the range for IgE was narrower than in young adults. Cholesterol, high-density lipoprotein cholesterol, and triglyceride values increased with age, but decreased in individuals greater than or equal to 90 y. Among the trace elements, magnesium changed little, zinc and lead decreased, and copper values increased with age. Total triiodothyronine and thyroxine decreased, with concomitant increases in thyroid-stimulating hormone. More individuals had increased microsomal antibodies and thyroglobulin titers in the aging population than in the young. In men, the free, percent free, bioactive, and total testosterone values decreased, but luteinizing hormone (LH) and follicle-stimulating hormone (FSH) values increased. In women, estrone and estradiol values decreased, with concomitant increases in LH and FSH. Androstenedione and progesterone decreased in both sexes.(ABSTRACT TRUNCATED AT 400 WORDS)

References

Sztefko, K. and P. Szybowska (2012). "Interpretation of hormone levels in older patients: points for consideration." Int J Endocrinol 2012: 712425 PMID: 22666247

Tietz, N. W., D. F. Shuey, et al. (1992). "Laboratory values in fit aging individuals--sexagenarians through centenarians." Clin Chem 38(6): 1167-85 PMID: 1596990