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The presence of abnormal proteins, primarily a monoclonal antibody produced by a plasma cell myeloma, will result in the hyperviscosity of a serum or plasma sample. Such highly viscous samples are difficult to pipette and may cause falsely low results in autoanalyzers for which sampling occurs through syringe-controlled sampling, where short sampling is possible. Compare this process to attempting to sip honey through a straw. Extra pressure is required to accomplish the task, and even where possible, the ability to accurately aspirate and dispense is compromised.
Many autoanalyzers are equipped with pressure sensors that will alert operators to the need to re-test the sample after checking for clots and sample viscosity.
For manual procedures where operators pipette the samples using a micropipette, such hyperviscous samples must be handled with caution to ensure that intended volumes are being added with accuracy. Occasionally, it will be necessary to first dilute the sample using pipette tips with a larger bore and intended for larger sample volumes to overcome the matrix effect.