BACKGROUND: Serum protein electrophoresis (SPE) and immunofixation electrophoresis (IFE) are used in the diagnosis and monitoring of plasma cell dyscrasias. IFE is considered the most sensitive method for the detection of monoclonal proteins (M-proteins), but it is not quantitative. The goal of this study was to establish the analytical sensitivity and diagnostic performance of SPE on the Sebia Hydrasys using HYDRAGEL 30 PROTEIN(E) β1-β2. METHODOLOGY: Patient sera with a previously identified M-protein (IgG, IgA or IgM) were serially diluted with a normal serum pool and electrophoresed on the Sebia Hydrasys using HYDRAGEL 30 PROTEIN(E) β1-β2. The SPE gels were individually interpreted by five independent observers and IFE was performed on selected samples. Limit of detection was determined as the lowest concentration of M-protein band visible on the gel. SPE diagnostic performance was evaluated against the "gold standard" IFE according CLSI EP12-A2 guidelines. RESULTS: Detection limit was comparable among all M-proteins migrating in the gamma region, IgG-κ (0.18±0.08g/L; n=6), IgG-λ (0.36±0.25g/L; n=8), IgA-κ (0.40±0.13g/L; n=7), IgA-λ (0.37±0.23g/L; n=4), IgM-κ (0.47±0.20g/L; n=13) and IgM-λ (0.29±0.24g/L; n=6). Percentage agreement with IFE for IgG and IgA in the gamma region ranged from 65% to 100%, whereas IgM migrating in the gamma region and immunoglobulins co-migrating with alpha or beta globulins, showed poor (0-38%) agreement. CONCLUSIONS: This study evaluates the analytical sensitivity and diagnostic performance of SPE on the Sebia Hydrasys using HYDRAGEL 30 PROTEIN(E) β1-β2. There was acceptable agreement between SPE and IFE for IgG-κ/λ and IgA-κ/λ migrating in the gamma region, suggesting that repeating IFE for samples with these isotypes, when the previous IFE and second SPE are both negative, may not be necessary.