Nephrotic range pseudoproteinuria in a tolmetin-treated patient

Area of Science:

• Nephrology
• Clinical Chemistry
• Pharmacology

Background:

• Routine urinalysis is crucial for monitoring kidney health.
• Tolmetin, a nonsteroidal anti-inflammatory drug (NSAID), is sometimes prescribed for inflammatory conditions.
• Acid precipitation testing is a common method for detecting proteinuria.

Observation:

• A patient with systemic lupus erythematosus (SLE) exhibited pseudoproteinuria (false-positive proteinuria).
• This misleading result was observed during routine urinalysis screening.
• The pseudoproteinuria was detected using an acid precipitation method for proteinuria assessment.

Findings:

• False-positive proteinuria results from acid precipitation testing in patients treated with tolmetin can occur.
• The magnitude of this false positivity has not been previously quantified.
• Nephrotic range pseudoproteinuria was observed in the presented SLE patient.

Implications:

• Clinicians should be aware of potential false-positive proteinuria results in tolmetin-treated patients.
• Alternative methods for proteinuria testing may be necessary for accurate diagnosis in these patients.
• Misleading urinalysis results can impact patient management and treatment decisions.