Abstract:

Objective To investigate the interference of endogenous urea in the determinations of thyroglobulin antibody（TgAb）,thyroid peroxidase antibody（TPOAb） and thyroid-stimulating hormone（TSH） by chemiluminescence immunoassay（CLIA）. Methods CLIA was used to determine the levels of serum TgAb,TPOAb and TSH in 30 patients with renal function failure before and after dialysis. Different levels（20,10,30,40,50 and 60 mmol/L） of urea were added to the mixed sera of healthy subjects,and the changes of TgAb,TPOAb and TSH levels were compared. The 800 U/L urease was added to serum samples from patients with renal function failure before and after dialysis,and the changes of TgAb,TPOAb and TSH levels were compared. Results Serum levels of TgAb,TPOAb and TSH of patients with renal function failure after dialysis were higher than those before dialysis（P<0.001）. There was no statistical significance for TPOAb and TgAb in TPOAb<15.0 IU/mL and TgAb<15.0 IU/mL dialysis patients before and after dialysis（P>0.05）. With the increasing of urea in the mixed sera of healthy subjects,the levels of TgAb,TPOAb and TSH were gradually decreased. After adding 800 U/L urease,there was no statistical significance in TgAb,TPOAb and TSH levels before and after dialysis in patients with renal function failure（P>0.05）. Conclusions High level of endogenous urea can interfere with the determinations of TgAb,TPOAb and TSH by CLIA. The addition of urease can eliminate the interference of endogenous urea.

Key words: Urea, Chemiluminescence immunoassay, Urease, Renal function failure