Reference distributions for the negative acute-phase proteins, albumin, transferrin, and transthyretin: a comparison of a large cohort to the world's literature.

Clinical interpretation of the acute-phase proteins--albumin, transferrin, and transthyretin--has been hampered by the lack of accurate and precise methods for quantifying the levels and a stable and respected reference material. Now that these issues have been addressed, the community is faced with the need for credible age- and gender-specific reference values. The number of publications that address this issue, even for an analyte as familiar as albumin, is small and, in most cases, such publications lack the relevant data that would allow a combined experience to be created. We have identified 40 studies that meet our criteria: a description of the study participants' health status, of the statistical methodology, and of the laboratory technique and/or reference material used. Few of these studies reported values stratified by gender. A summary of the published median levels by age is presented for the three analytes, along with our own age- and gender-specific medians based on a large cohort. Ten of the studies presented a 95 percent reference range, in close agreement with ours where selection was based upon reported diagnosis rather than upon determination of individual health status. This meta-analysis provides support for the reliability of our recently published methodology and reference data for the clinical interpretation of individual albumin, transferrin, and transthyretin values. As with most laboratory measurements, clinical interpretation requires that other laboratory and clinical factors be considered.