Serologic associations of anti-cytoplasmic antibodies identified during anti-nuclear antibody testing.
BACKGROUND
There are currently no guidelines concerning additional laboratory testing for specific autoantibodies among anti-nuclear antibody-negative sera with an anti-cytoplasmic staining pattern identified by indirect immunofluorescence assay. Moreover, few data are available that address this laboratory situation.


METHODS
We performed specific autoantibody assays in 200 sera with an anti-nuclear antibody titer < or =1:32 and a cytoplasmic titer (undefined staining pattern) of > or =1:64, identified sequentially in the course of routine anti-nuclear antibody testing.


RESULTS
A total of 85 sera (42.5%) were positive in one (n=57) or more (n=28) of the specific autoantibody tests performed. Autoantibodies identified were antimitochondrial (15%), antimicrosomal (13%), anti-neutrophil cytoplasmic (10%), anti-smooth muscle (6%), anti-parietal cell (4%), and extractable nuclear antigen (8.5%, including histones, SSA, SSB, Sm, Jo-1 or Scl-70). A positive result in one or more of these assays was more frequent at anti-cytoplasmic titers > or =1:1024 (77.8%) than at titers of 1:64-1:128 (7%) (chi2=25.3, p<0.001).


CONCLUSIONS
The present data demonstrate that undefined anti-cytoplasmic staining in anti-nuclear antibody-negative sera is associated with, although not necessarily caused by, a high frequency and wide range of specific autoantibodies. Further work is needed before specific recommendations can be made concerning follow-up in subjects with this laboratory finding.
Craig
Wendy Y
WY
Foundation for Blood Research, Scarborough, ME 04070-0190, USA. wcraig@fbr.org
Ledue
Thomas B
TB
Collins
Marilyn F
MF
Meggison
William E
WE
Leavitt
Lynda F
LF
Ritchie
Robert F
RF
D019268:Antibodies, Antineutrophil Cytoplasmic / Q000097:blood*; D000974:Antibodies, Antinuclear / Q000097:blood*; D001323:Autoantibodies / Q000097:blood*; D003593:Cytoplasm / Q000276:immunology*; D005455:Fluorescent Antibody Technique; D006801:Humans; D012698:Serologic Tests
D019268:Antibodies, Antineutrophil Cytoplasmic; D000974:Antibodies, Antinuclear; D001323:Autoantibodies