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

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.

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 m² 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.

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.