Discrepant Urinary Findings Between Dipstick Protein and Sulfosalicylic Acid Test in a Patient With Hyaline Casts: A Case Report.
Yifei Jia, Binquan Chu, Fengjun Chen et al.
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Case in brief
A 31-year-old woman with hemophagocytic lymphohistiocytosis underwent routine urinalysis after allogeneic hematopoietic stem cell transplantation. Automated sediment analysis showed elevated hyaline casts (5.8/μL), despite a negative dipstick protein result; sulfosalicylic acid testing was positive (++). Serum creatinine subsequently rose from 53 μmol/L to a peak of 132 μmol/L, with an estimated glomerular filtration rate nadir of 46.3 mL/min/1.73 m². On follow-up, dipstick and sulfosalicylic acid tests were negative and hyaline casts had decreased to 0.5/μL. The urinary findings were transient during evolving acute kidney injury.
What made this case unusual
The discordance between negative dipstick protein and positive sulfosalicylic acid testing, alongside increased hyaline casts, occurred during evolving acute kidney injury; the material detected by sulfosalicylic acid was not molecularly identified.
Diagnostic / clinical pearl
When increased hyaline casts accompany a negative dipstick protein result in a high-risk patient, confirmatory sulfosalicylic acid testing and correlation with renal-function trends may help interpret the finding.