External quality assessment of autoantibodies detection in clinical laboratories during 2006—2011 in China

Objective To evaluate the performance of antinuclear antibody(ANA) detection in clinical laboratories. Methods There were 2 external quality assessments(EQA) scheme for nuclear antibody detection.The panel consisting of 5 samples was distributed.Each participant laborotory of the EQA program was required to report the ANA qualitative results, patterns, titers and anti-double strain DNA(dsDNA) antibody, anti-extractable nuclear antigen(ENA) antibody, the percent agreements of which were calculated respectively. Results The number of laboratories performing ANA test with IIF increased from 77.6%（149/192）in 2006 to 82.2%（342/416） in 2011, while the number of laboratories performing ANA test with ELISA was in the range of 14.5%（53/365） and 16.0%（52/326）.The positive percent agreements of IIF was over 98%.The positive percent agreement of ELISA were all over 90%.IIF showed more satisfying positive percent agreements than ELISA every year.Over 90% of the laboratories reported correct results for samples with granular ANA pattern except 0613 and 0624.Over 95% of the laboratories reported correct results for samples with homogeneous ANA pattern.Two samples with centromere pattern were correctly detected by 88.5%（161/182），79.0%（147/186）of the laboratories in 2007, while the sample with centromere pattern was correctly detected by 98.4%（299/304）, which indicated an improvement in the detection of centromere pattern. In ANA positive results, the lowest percentage of the laboratories reporting the median result was 36%（94/261）, while the highest percentage was only 85.5%（224/262）.The satisfied results of anti-ENA antibody were over 90%.And those of anti-dsDNA antibody was over 85%. Conclusions IIF is the most common method for ANA screening in clinical laboratories.ELISA is also used in some laboratories.The two methods reported satisfying results in ANA test.The detection of anticentromere antibodies is improved.But the results of ANA titer reported are unsatisfactory. ANA detection in routine practice needs to be improved by standardization.（Chin J Lab Med, 2012,35:271-276） Key words: Autoantibodies; Autoimmune diseases; Quality control; Clinical laboratory techniques