Discrepant Urinary Findings Between Dipstick Protein and Sulfosalicylic Acid Test in a Patient With Hyaline Casts: A Case Report

ABSTRACT Background Routine urinalysis is a foundational screening tool; however, increased hyaline casts accompanied by a negative dipstick protein result may complicate laboratory interpretation. In patients at high risk of acute kidney injury (AKI), this discordant pattern may warrant confirmatory protein testing and correlation with renal‐function trends. Case Presentation A 31‐year‐old female with hemophagocytic lymphohistiocytosis (HLH) underwent routine urinalysis after allogeneic hematopoietic stem cell transplantation (allo‐HSCT). Automated sediment analysis detected elevated hyaline casts (5.8/μL), whereas the concurrent dipstick protein result was negative. Protocol‐based sulfosalicylic acid (SSA) verification yielded a visually graded positive (++) reaction. Serial renal‐function monitoring showed that serum creatinine (SCr) increased from 53 μmol/L on December 10 to 62 μmol/L on December 12, followed by progressive deterioration and a peak SCr of 132 μmol/L with an estimated glomerular filtration rate (eGFR) nadir of 46.3 mL/min/1.73 m 2 on December 24. Follow‐up urinalysis on December 26 showed normalization of this urinary phenotype, with negative dipstick protein, negative SSA testing, and a decrease in hyaline casts to 0.5/μL. These findings were consistent with a transient urinary abnormality occurring during evolving AKI rather than persistent kidney disease. Conclusion In this high‐risk post‐transplant patient, increased hyaline casts with negative dipstick protein and positive SSA testing occurred during evolving AKI and resolved as renal function improved. The finding may indicate acid‐precipitable non‐albumin urinary material, but its molecular basis and relationship to tubular injury remain uncertain.