Current practices in antinuclear antibody testing: results from the Belgian External Quality Assessment Scheme.
BACKGROUND
This study aimed to assess the state-of-the-art of antinuclear antibody (ANA) testing as practiced in the Belgian and Luxembourg laboratories, using the results obtained in the Belgian National External Quality Assessment Scheme from 2000 to 2005.


METHODS
During this period, nine samples with different specificities were sent for analysis. Participants were surveyed for methodology used and were asked to report staining pattern and titer of ANAs. In 2002, an attempt was made to improve the comparability of quantitative ANA results by the provision of a commercial reference material and to relate observed differences to methodology.


RESULTS
With one exception, all participants employed a microscope-based indirect immunofluorescence assay with human epithelial cell line 2 cells. Most laboratories were accurate in describing the pattern. The percentage of unacceptable answers was greater for samples with borderline levels of antibody and for samples showing a cytoplasmic pattern. An improvement in the detection of anticentromere antibodies was observed. For all samples, a wide range of titers was reported. The provision of the secondary reference preparation led to improved inter-laboratory concordance. Comparison of methodology variables revealed a correlation between unstandardized titers and the power of the lamp of the microscope and the use of a dark room.


CONCLUSIONS
The EQAS results presented in this work provide valuable insights into the state of the art of ANA testing as practiced in the Belgian and Luxembourg Laboratories and illustrate the important value of a national EQAS for ANA testing as a tool to improve performance and interlaboratory comparability of laboratory results.
Van Blerk
Marjan
M
Department of Clinical Biology, Scientific Institute of Public Health, Brussels, Belgium. m.vanblerk@iph.fgov.be
Van Campenhout
Christel
C
Bossuyt
Xavier
X
Duchateau
Jean
J
Humbel
René
R
Servais
Geneviève
G
Tomasi
Jean-Paul
JP
Albert
Adelin
A
Coucke
Wim
W
Libeer
Jean-Claude
JC
D000974:Antibodies, Antinuclear / Q000032:analysis*; D001530:Belgium; D019084:Fluorescent Antibody Technique, Indirect / Q000592:standards*; D006801:Humans; D011785:Quality Assurance, Health Care; D012015:Reference Standards; D011795:Surveys and Questionnaires
D000974:Antibodies, Antinuclear