Nephrotic range pseudoproteinuria in a tolmetin-treated patient

False-positive proteinuria by acid precipitation testing in tolmetin-treated patients has been noted on routine urinalysis screening. However, the magnitude of such false positivity has not been previously reported. We present a patient with systemic lupus erythematosus who presented with nephrotic range pseudoproteinuria using an acid precipitation method of testing. This misleading laboratory result and alternative methods of testing for proteinuria in tolmetin-treated patients are discussed.