External quality assessment of antinuclear antibodies titer report from clinical laboratories in 2012 in China

Objective To evaluate the agreement of antinuclear antibody (ANA) titer reported in clinical laboratories and analyze possible problems in clinical laboratories. Methods Experiment survey.The panel consisting of 5 samples was distributed to 533 laboratories.Each panel contains one negative sample and 4 positive samples,which were from individuals of autoimmune disease.ANA titer system was divided into traditional titer system with two-fold dilution and titer system with 3.2 times dilution.Clinical laboratories were required to report the ANA titers and initial screening dilution according to the standard used in routine work.Results were expressed as median titers and range for acceptable performance.As to titer system with two-fold dilution,acceptable performance on proficiency testing was defined by a result equal to median titer±two two-fold dilutions.While as to titer system with 3.2 times dilution,acceptable performance on proficiency testing was defined by a result equal to median titer±3.2 times dilutions.The laboratories percentages with acceptable performancewerecalculated to evaluate their agreements. Results 412 laboratories reported ANA titer results,of which 11.9% (49/412) reported results with two-fold dilution titer system,88.1% (363/412) reported results with 3.2 times dilution titer system.The median titers of sample 1211,1212,1213 and 1215 reported with two-fold titer system were 1∶640,1∶320,>1∶1280 and 1∶160,respectively.The agreement within the median ANA titer reported with two-fold dilution titer system ranged from 24.5% (12/49) to 57.1% (28/49) and the lowest percentage of the results within the acceptable limits was 87.8% (43/49).The median titers of sample 1211,1212,1213 and 1215 reported with 3.2 times dilution titer system were 1∶1000,1∶1000,>1∶3200 and 1∶320,respectively.The agreement within the median ANA titer reported with 3.2 times dilution titer system ranged from 63.3% (31/49) to 83.7% (41/49).The lowest percentage of the results within the acceptable limits was 98.0% (48/49). Conclusions The results of ANA titer reported are unsatisfactory.Standardization for reagent,microscopy,procedure and result interpretation is necessary to improve the agreement of ANA titer report in different laboratories.(Chin J Lab Med,2013,36:648-652) Key words: Antibodies; antinuclear; Laboratory techniques and procedures; Quality control