Misleading Urinary Protein Pattern in a Patient with Hypogammaglobulinemia: Effects of Mechanical Concentration of Urine

Usually urine protein electrophoresis (UPE) gives rise to distinctive patterns that indicate the source of proteinuria. However, abnormalities of endogenous protein synthesis and peculiarities attributable to mechanical concentration of the sample before analysis can cause misinterpretation. Here we describe the analysis of urine from a patient with hypogammaglobulinemia in which a probable mixed pattern appeared as pure glomerular proteinuria as a result of altered immunoglobulin synthesis.A 72-year-old, Caucasian male patient with a 1-year history of chronic lymphocytic leukemia and a 20-year history of insulin-requiring type 2 diabetes with diabetic retinopathy and neuropathy was admitted to the hospital because of syncope. Selected test results at the time of admission were as follows (reference intervals in parentheses): urea nitrogen, 0.22 g/L (0.07–0.22 g/L); creatinine, 0.01 g/L (0.006–0.014 g/L); total protein, 55 g/L (62–82 g/L); albumin, 33 g/L (35–50 g/L); IgG, 1.7 g/L (7.2–16.8 g/L); IgA,0.2 g/L (0.69–3.8 g/L); IgM, 0.1 g/L (0.63–2.7 g/L); phosphorous, 0.022 g/L (0.025–0.048 g/L); potassium, 3.7 mmol/L (3.5–5.1 mmol/L); and glucose, 2.35 g/L (0.65–1.1 g/L, fasting). Sodium, bicarbonate, and chloride were within the health-related reference intervals. Urinalysis was remarkable for occasional squamous epithelial cells and hyaline casts, a glucose >2.5 g/L, and 6.4 g protein/24 h, with a volume of 1.5 L (reference interval, <200 mg/24 h). Hematologic studies were unremarkable except for a white blood cell count of 115 000/mm3 with 86% lymphocytes.A 24-h urine specimen was obtained without the use of preservatives. Urinary total protein was measured using pyrogallol red-molybdate with a kit (Biotrol urine proteins, Biotrol USA) on a Cobas Fara II (Roche Diagnostics), which was modified by use of a linear interpolation calibration mode with calibrators down to 50 mg/L to optimize accuracy in the low range. Before electrophoresis, urine samples were concentrated mechanically using Minicon-B15 concentrators (Amicon).Protein electrophoresis was …