MON-477 Anti-Streptavidin Interference in Multiple Hormones Immunoassays: Case Report

Automated immunoassays are the most commonly current methods used in clinicial laboratory to hormone tests, due short turnaround time and high specificity and sensibility. However immunoassays are not free from interferences. Several immunoassays use biotin-streptavidin interaction to anchor antigen-antibody complexes in solid phase and so are susceptible to biotine intake or anti-streptavidin antibody. In sample with these interferents, the results in competitive assays are falsely high and in non-competitive assays are falsely low. OBJECTIVE: To report a case of multiple hormones immunoassay interference by an anti-streptavidin antibody. MATERIAL AND METHODS: A 11-years-old boy with child obesity, and no other symptoms, had discordant laboratory results with markedly elevated free T4, total T4 and total T3 with normal TSH. Repeated measurements in the same sample and in a new collected sample confirmed the initial results and revealed low PTH and high TRAb without hypocalcemia or hyperthiroidism clinical pictures. All the parameters were measured on the automated Cobas e602, Roche plataform.The patient and your family denied biotin ingestion, so anti-streptavidin interference could explain the multiple interference.The serum was pre-incubated with streptavidin microparticles during an hour and centrifuged for 10min (3000 rpm) to removed the analytical interference. RESULTS: The results of post-incubation with microparticles were all in the normal range. Three control samples were not affected by the incubation. Since luminescence is inversely proportional to analyte concentration in competitive assays, low signals lead to falsely high levels (like in free T4, total T4, Total T3 and TRAb in our patient). The reverse occurs with immunometric assays, in which low signals result in falsely reduced values (like in PTH in our patient). CONCLUSION: In literature, streptavidin antibodies seem to be a rare occurrence. In samples with biotin or anti-streptavidin suspection, pre-incubation with streptavidin microparticles is a simple and effective procedure to remove this interference.