Jiun-Chi Huang, Shang-Jyh Hwang, Hung-Chun Chen

一蛋白尿病患尿液試紙和尿液蛋白/肌酸酐比值不相符的思考分析

Thinking Approach for a Patient of Proteinuria with Discrepancy between Urine Dipstick and Urine Protein-to-Creatinine Ratio

黃俊祺 黃尚志 陳鴻鈞

Jiun-Chi Huang, Shang-Jyh Hwang, Hung-Chun Chen

高雄醫學大學附設醫院 内科部 腎臟內科

Division of Nephrology, Department of Internal Medicine,

KaohsiungMedicalUniversityHospital, Kaohsiung, Taiwan

Urine dipstick is widely used for screening patients with kidney disease and proteinuria. It mainly detects albumin in the urine. The drawback should be compensated by sulfosalicylic acid test, which detects all protein in the urine.However, sulfosalicylic acid test was gradually omitted and replaced by spot urine protein-to-creatinine ratio, as its convenience and reliability to measure daily protein loss in the urine, compared to collecting 24-hour urine. We reported a case with heavy proteinuria, and found mismatch between the above two modalities.

A 62-year-old male with chronic kidney disease and hypertension, complaining of foamy urine for 3 months, presented to our nephrology out patient department. His urine dipstick for protein was only “+”, but nephrotic range of proteinuria (8.28 mg/mg) was noted by measuring spot urine protein-to-creatinine ratio. He was admitted for advanced study of nephrotic syndrome.

Serum IgG, IgA and IgM levels were depressed. HbsAg, IgG Anti-HCV and cryoglobulin were all negative. However, serum albumin level was 4.46 g/dL, which is unexpected in a patient with nephrotic syndrome. Serum protein electrophoresis was carried out, but it showed no abnormal peak.

Immunofixation electrophoresis demonstrated monoclonal lambda light chain in both serum and urine. Renal biopsy was performed as well as bone marrow aspiration. Immature plasma cells were more than 25% in bone marrow study. Skull x-ray showed punched-out osteolytic lesions. Therefore, this patient was diagnosed of multiple myeloma with lambda light chain monoclonal gammopathy.

It reminds us that when discrepancy between urine dipstick and spot urine creatinine-to-protein ration in a patient with proteinuria, we should notice the probability of Bence Jones protein and search for evidence of multiple myeloma.

Key words：Proteinuria, Urine dipstick, Chronic kidney disease

關鍵字：蛋白尿, 尿液試紙, 慢性腎衰竭