Abstract: Objective　To investigate the practical application of the interference screening and quantification for urine analysis in clinical chemistry according to the  Clinical and Laboratory Standards Institute (CLSI) EP7-A2 document，and evaluate the interference effects of aminoglycoside antibiotic in urine total protein determination.   Methods　According to the CLSI EP7-A2 document， fresh urine specimens with the urine total protein concentrations of 77， 146， 538 and 832 mg/L were collected, and the etimicin sulfate solution of 3 times maximum therapeutic dosage per liter of urine was added. The interference was screened by pyrogallol red-molybdate assay. The interference effects were quantified, and the etimicin sulfate solution and distilled water were added to form a concentration gradient （0, 0.15, 0.30, 0.45 and 0.60 mg/mL） of the interferent for each group. By multiple regression analysis, the degrees of interference at any interferent concentrations were estimated.  Results　After adding 0.6 mg/mL of etimicin sulfate solution into 4 groups （with the urine total protein concentrations of 77，146，538 and 832 mg/L）， the lower confidence limit of interference effect exceeded the allowable error at the medical decision concentration. Adding 5 concentrations of the etimicin sulfate solution into each specimen group， the five-level dose-response series (0, 0.15, 0.30, 0.45 and 0.60 mg/mL) all showed a linear relationship, and the linear equations were Y＝202X－1.2，Y＝187.3X＋4，Y＝325.3X＋0.6 and Y＝345.3X＋6.4. It indicated that the positive interference effects caused by etimicin sulfate while adding 0.08，0.15，0.35 and 0.50 mg/mL of the interferent into each urine group, all exceeded the allowable error.  Conclusions　The etimicin sulfate causes a positive interference in the pyrogallol red-molybdate assay for urine total protein determination. Clinical laboratories need to perform the interference tests to screen potential interferents, quantify interference effects, evaluate potential hazards and establish meaningful interference claims.

Key words: Total protein, Urine, Aminoglycoside antibiotic, Interference analysis