The saline needle-wash specimen is analyzed with the Siemens calcitonin reagent assay on the Siemens Immulite 1000. The Siemens calcitonin assay is a solid-phase, 2-site chemiluminescence enzyme-labeled immunometric assay. The solid-phase bead is coated with monoclonal murine anticalcitonin. The specimen and alkaline phosphatase-conjugated goat polyclonal anticalcitonin antibody are incubated to bind calcitonin into an antibody sandwich complex. In the presence of alkaline phosphatase, the chemiluminescent substrate, which is a phosphate ester of adamantyl dioxetane, produces light that is proportional to the concentration of the calcitonin in the specimen.(Package insert: IMMULITE 2000 Calcitonin, Siemens Medical Solutions Diagnostics, Los Angeles, CA. PIL2KCL-15, 2008-07-29)
For all samples with calcitonin concentrations >50 pg/mL, a dilution series is performed. A linear dilution excludes hooking and most major interferences. Samples that contain calcitonin concentrations <50 pg/mL are spiked with exogenous calcitonin to identify possible interferences that may cause a false-low result.