For assays that use antibodies, heterophile antibodies (human anti-sheep, mouse, rat, or goat antibodies) in the patient sample may interfere with them. Patients regularly exposed to animals or who have received immunotherapy or diagnostic procedures utilizing immunoglobulins or immunoglobulin fragments may produce antibodies that interfere with immunoassays, causing erroneous results. If this is the case, it is recommended that LC-MS assays be used to avoid such interferences.
Hemolyzed samples (concentrations greater than 50 mg/dL), lipemic, or severely icteric samples may cause falsely elevated results in those assays that use spectrophotometric methods for analysis. It is recommended that these samples be avoided if possible.
Other potential interferences in the patient sample could be present and may cause erroneous immunoassay results. Some examples documented in the literature include rheumatoid factor, endogenous alkaline phosphatase, fibrin, and proteins capable of binding to alkaline phosphatase.
