Stepwise Interpretation of Albumin Fraction Abnormalities on Serum Protein Capillary Electrophoresis in Nephrotic Syndrome: A Case Series.

Serum protein electrophoresis (SPEP) is commonly used in the diagnostic evaluation of nephrotic syndrome (NS) to rule out monoclonal gammopathies. However, NS itself and various other factors may cause transient bisalbuminemia, resulting in albumin fraction irregularities in capillary SPEP and complicating interpretation. This study proposes a stepwise approach for interpreting albumin fraction irregularities, illustrated through three representative cases of NS. Case 1: a 44-year-old woman with isolated proteinuria, Case 2: a 36-year-old woman with diabetic foot infection, and Case 3: a 58-year-old man with ankylosing spondylitis, all presenting with nephrotic-range proteinuria. On initial SPEP case 1 exhibited a distinct sharp peak, while cases 2 and 3 showed irregular bands between the albumin and α1 regions. A stepwise interpretative approach was applied: First, technical errors were excluded by repeat analysis using alternative capillaries on the same analyzer. Second, potential biochemical interferences were evaluated. Third, SPEP was repeated using freshly collected samples. Fourth, persistent albumin fraction irregularities prompted consideration of biochemical albumin modifications, such as glycosylated or carbamylated forms. Fifth, other causes including drugs, heavy metal toxicity, liver disease, and systemic inflammation were excluded. Finally, additional tests such as immunofixation electrophoresis were performed to rule out monoclonal proteins. In the absence of monoclonal proteins, the condition was interpreted as bisalbuminemia related to NS. Using this approach, transient bisalbuminemia was considered the most likely cause in Cases 1 and 2, whereas the disappearance of the irregular band in Case 3 suggested a preanalytical artifact. Systematic interpretation of albumin fraction irregularities can help distinguish true pathology from benign or artifactual patterns in patients with NS.