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Transferrin-derived TIBC, a flagged but normal result
Martin Safran1, James Corines1, Matthew Elkins1
1Department of Pathology & Laboratory Medicine, State University of New York, Upstate Medical University, Syracuse, NY, USA.
Background:
Total Iron Binding Capacity (TIBC) is routinely used in the diagnosis and management of iron disorders. TIBC can be derived by multiplying transferrin value by a conversion factor. Usage of different conversion factors in calculating patient TIBC results and the upper- and lower-limit of TIBC reference intervals inadvertently exist. Its commonality and effect on diagnosis and clinical management remain unknown.
Methods:
Electronic medical records and laboratory operation procedures were examined to identify and analyze the root of cause of discordant patients' results between transferrin and transferrin-derived TIBC. Internet-searching was conducted for the information, posted on-line by 21 randomly selected CLIA-certified clinical laboratories in the USA, on the conversion factors for calculation of the lower- and upper-limit of TIBC reference intervals.
Results:
Discordance between the transferrin and transferrin-derived TIBC results were found to cause no adverse impact on quality of patient care. Of the 21 laboratories, 14 (66%) used different conversion factor values ranging 0.74-1.44 for calculating lower-limit of TIBC reference interval, and 1.07-1.42 for the upper limit, with the absolute difference values ranging 0.01-0.67.
Conclusion:
Our study suggested that usage of different conversion factors in calculating the upper- and lower-limits of TIBC reference intervals be commonly used by the CLIA-regulated clinical laboratories in the USA but remain unnoticed. The phenomenon of discordant results may likely occur to transferrin results near the lower- or upper-limit of reference range and unlikely cause adverse impact on quality of patient care.
