Biotin interference in TSH, FT4, and FT3 assays based on the LOCI technology: Identifying interference by dilution.

Abstract

Although biotin interferences in TSH, FT3, FT4, and other biotinylated antibody-based assays manufactured by Roche Diagnostics have been well studied, there are relatively few reports on biotin interference in biotin-based assays manufactured by other companies. We investigated biotin interferences in TSH, FT4, and FT3 assays based on the LOCI (luminescent oxygen channeling assay) technology using the Dimension Vista 1500 analyzer (Siemens). We prepared four serum pools using leftover specimens. Three serum pools were prepared initially for the original study but the 4th pool was prepared three months later. The aliquots of serum pool one and two were supplemented with various amounts of biotin (50 -1200ng/mL) followed by determination of TSH, FT4, and FT3 concentrations. The aliquots of third pool were also supplemented with biotin to investigate whether 1:3 dilution could identify biotin interference. Aliquots of serum pool four were supplemented with biotin in order to study reproducibility of our original data. We observed significantly elevated FT3 levels at biotin concentration of 100ng/mL. In contrast, FT4 levels were falsely elevated but TSH levels were falsely decreased at a biotin level of 500ng/mL. We also observed nonlinearity in dilution experiment. We conclude that FT3 assay is most susceptible to biotin interference (threshold: 100ng/mL) while the FT4 and TSH assays are less affected (threshold: 500ng/mL). In addition, we also observed nonlinearity upon 1:3 dilution, which may indicate biotin interference (or interference from other compounds).