The serum protein electrophoresis pattern (SPEP)2 for an 82-year-old female patient with known monoclonal gammopathy of undetermined significance demonstrated 2 aberrant protein bands, one in the α2-β1 interzone (Fig. 1A, fat arrow) and one in the β1-β2 interzone (Fig. 1A, thin arrow). The immunofixation electrophoresis (IFE) (Fig. 1B) revealed a large IgA κ paraprotein in the β1-β2 interzone (Fig. 1B, thin arrow) but only a very faint IgA heavy-chain paraprotein corresponding to the large α2-β1 interzone band (Fig. 1B, fat arrow). 

Serum IFE (A), the initial SPEP using a hemolyzed sample (B), and the SPEP performed with a nonhemolyzed serum sample(c).

The fat arrows mark the faint IgA heavy chain and the band corresponding to the haptoglobin–hemoglobin protein complex, respectively, migrating together within the α2-β1 interzone. 


  1. Why would a dense band on SPEP and a corresponding faint band on IFE be a red flag for a discrepant result?
  2. What are possible causes of additional α2-β1 interzone migrating protein bands?
  3. What is the most likely type of laboratory error involved in this case: preanalytical, analytical, or postanalytical?

Read the article here for the answers.