[Quality control of radioligand assay for glutamic acid decarboxylase antibody].
OBJECTIVE
To supply the quality control for glutamic acid decarboxylase antibody (GAD-Ab) measurement using radioligand assay.


METHODS
The quality control of GAD-Ab determined with radioligand assay in 83 batches was analyzed.


RESULTS
The intra-assay coefficient of variation (CV) was 4.3% to approximately 8.3% and the inter-assay CV was 7.1% to approximately 10.8%. A ratio of signal to noise (S/N) with 15 or more was defined as a valid measurement. Of the 83 batches, 67 batches (80.7%) met with the standard and the other 16 (19.3%) were not qualified. When the results were analyzed according to the season, the failure rate in summer was significantly higher than that in winter (38.5% vs 4.8%, P < 0.05). In addition, the mean value of S/N in summer was significantly lower than that in winter ( 14.1 +/- 7. 3 vs. 21.5 +/- 5.2, P < 0.01). Among the failed batches, 68.8% (11/16) was caused by TBST buffer and 50% (8/16) due to the increased temperature of TBST buffer. Other causes for the failure included the invalidation of reagents for in vitro transcription and translation.


CONCLUSIONS
TBST buffer and other influential factors of radioligand assay in determining GAD-Ab, should be controlled strictly to ensure a reliable and repeatable result.
Huang
Gan
G
Institute of Metabolism and Endocrinology, Xiangya Second Hospital, Central South University, Changsha 410011, China.
Zhou
Zhi-guang
ZG
Peng
Jian
J
D001323:Autoantibodies / Q000097:blood*; D003922:Diabetes Mellitus, Type 1 / Q000097:blood / Q000276:immunology*; D005968:Glutamate Decarboxylase / Q000276:immunology*; D006801:Humans; D011786:Quality Control; D011869:Radioligand Assay; D012189:Retrospective Studies; D012621:Seasons
D001323:Autoantibodies; D005968:Glutamate Decarboxylase