2 mL serum from a plain red top tube. Allow sample to clot in an upright position for at least 60 minutes, then centrifuge sample and transfer serum to a plastic transport tube within 2 hours of collection. Clearly label tube as serum from a plain red top tube. Refrigerate.
If definitive or possible monoclonal protein is present, immunotyping will be performed.
Note: consider ordering both serum protein electrophoresis and serum free light chains (SFLC) for the initial detection of monoclonal immunoglobulin protein (M-protein) in patients with suspected monoclonal gammopathies.