Reference distributions for the negative acute-phase serum proteins, albumin, transferrin and transthyretin: A practical, simple and clinically relevant approach in a large cohort

Inflammation is associated with diverse clinical conditions accompanied by characteristic changes in serum levels of the acute-phase proteins that can be used to stage the inflammatory process and evaluate the impact of treat ment. Some acute-phase proteins increase during inflammation, while others, such as albumin, transferrin, and transthyretin, decrease. The current stu dy reports reference ranges for serum levels of albumin, transferrin, and t ransthyretin based on a cohort of over 124,000 Caucasian individuals from n orthern New England, tested in our laboratory between 1986 and 1998. Measur ements were standardized against CRM 470 (RPPHS) and analyzed using a previ ously validated statistical approach. Individuals with laboratory evidence of inflammation (C-reactive protein of 10 mg/L or higher) were excluded. Th e levels of all three analytes varied by age, generally rising until the se cond or third decade of life and then decreasing thereafter. Albumin and tr ansthyretin levels were higher during midlife among males as compared to fe males; the maximum being at 25 years for albumin (5%) and 35 years for tran sthyretin (16%). In contrast, above the age of 10 years, transferrin levels were increasingly higher among females (7% at 20 years). When values were expressed as multiples of the age- and gender-specific median levels, the r esulting distributions fitted a log-Gaussian distribution. When patient dat a are normalized in this manner, the distribution parameters can be used to assign a corresponding centile to an individual's measurement simplifying interpretation. The ultimate interpretation of an individual's measurement relies upon the clinical setting. J. Clin. Lab. Anal. 13:273-279, 1999. (C) 1999 Wiley-Liss. Inc.