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Relative value of commercial kits for ANA testing
1Department of Medicine, University of Alberta, Edmonton, Alberta, Canada.
Aims:
We have tested the relative performance of 20 commercial ANA test kits along with that of our own laboratory to assess whether one was clearly superior.
Methods:
The sera were drawn from 3 pools that had all been pre-tested in our laboratory: patients with definite SLE; patients with non-connective tissue diseases (CTD), but where a positive FANA had been found; and normal blood donors. The tests were used in accordance with the recommendations of the specific supplier but in a routine serology laboratory.
Results:
Sensitivity and specificity ranged between 38 and 100%. While the negative predictive value of 4 ELISA kits was 100%, and most others were close, the HEp-2 kits were 100% in only 1 case. A positive predictive value of 100% was also seen with 1 kit.
Conclusion:
Some of the tests are clearly better than others, but the choice may differ depending on the clinical needs, e.g. preference for a good positive or negative predictive value. However, the ELISA kits offered better results than the immunofluorescent technique. Two of them had sensitivity/specificity of > 90%.