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Letters |
Department of Clinical Pathology, University Hospitals Leuven, Kapucijnenvoer 33, B-3000 Leuven, Belgium
a Author for correspondence. Fax 32 16 332896; e-mail xavier.bossuyt{at}uz.kuleuven.ac.be.
To the Editor:
Antibodies against extractable nuclear antigens (ENAs) are useful diagnostic markers for various autoimmune diseases. Anti-SSA and anti-SSB antibodies are found in Sjögren Syndrome (SS), anti-Sm antibodies are found in systemic lupus erythematosus (SLE), anti-RNP antibodies are found in mixed connective tissue disease (MCTD), and anti-Scl-70 antibodies are found in scleroderma. Antibodies against cytoplasmic Jo-1 and M2 are helpful markers for the diagnosis of, respectively, polymyositis and primary biliary cirrhosis. The antibodies can be identified by either counter immunoelectrophoresis (CIE) or immunoblotting. These techniques, however, are time-consuming, technically demanding, and do not provide for fast turnaround times. Over the last few years, alternative techniques such as ELISA and dot blot (DB) have been introduced. A DB technique from Biomedical Diagnostics recently has become available and has been evaluated for autoantibodies against ENAs by Ermens et al. (1). In the present study, we evaluated the same DB technique for autoantibodies against ENAs and against the cytoplasmic antigens Jo-1 and M2. The DB technique was compared with CIE for the detection of antibodies against ENAs and Jo-1 and with indirect immunofluorescence (IF) for the detection of antibodies against M2.
The DB technique was performed according to the manufacturer's instructions. CIE was performed as described by Walravens et al. (2). To detect antibodies against mitochondria by IF, we incubated sera for 30 min at room temperature with rat kidney and rat stomach sections at a 1:20 serum dilution, and then washed and incubated the sera with fluorescein isothiocyanate-labeled sheep anti-human immunoglobulin. Tissue sections were examined under ultraviolet light, using an Orthoplan Leitz Wetzler microscope. Mitochondrial antibodies appeared as discrete granular staining, predominantly in the distal tubules of the kidney and in the parietal cells of the stomach.
Table 1
shows the results of the method comparison study. The agreement
between CIE and DB for antibodies against ENAs was 99%, 98%, 99%,
100%, and 0%, for SSA, SSB, RNP, Sm, and Scl-70, respectively. The
medical records of the patients with CIE+/DB- SSA, CIE+/DB- SSB,
CIE-/DB+ SSB, and CIE-/DB+ RNP revealed symptoms typical for systemic
lupus erythematosus, SS, mixed connective tissue disease, and
SS, respectively. The three patients with CIE-/DB+ results for Scl-70
had symptoms typical for scleroderma. These data confirm the previously
reported (1) excellent sensitivities and specificities of DB
techniques for the detection of antibodies against ENAs. The agreement
between CIE/IF and DB for the detection of the cytoplasmatic
antigens Jo-1 and M2 was 100% and 93%, respectively. The patients
with IF+/DB- M2 had autoimmune hepatitis and chronic hepatitis C.
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IF detects various subtypes of anti-mitochondrial antibodies, but lacks the ability to detect specific antigens, such as the M2 subtype, which is highly specific for primary biliary cirrhosis. Therefore, DB is a valid alternative to CIE and IF for the detection of antibodies against ENA, Jo-1, and M2 with markedly faster turnaround time. The DB method is also more sensitive for the detection of anti-Scl-70 antibodies.
References
The following articles in journals at HighWire Press have cited this article:
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X. Bossuyt and A. Luyckx Antibodies to Extractable Nuclear Antigens in Antinuclear Antibody-Negative Samples Clin. Chem., December 1, 2005; 51(12): 2426 - 2427. [Full Text] [PDF] |
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X. Bossuyt, J. Frans, A. Hendrickx, G. Godefridis, R. Westhovens, and G. Marien Detection of Anti-SSA Antibodies by Indirect Immunofluorescence Clin. Chem., December 1, 2004; 50(12): 2361 - 2369. [Abstract] [Full Text] [PDF] |
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A. A.M. Ermens, A. J.M. Bayens, A. Crooymans, A. A.M. Broekman-van Hout, and H. L.P. van Duijnhoven Evaluation of a Simple Dot-Blot Method for the Detection of Anti-Neutrophil Cytoplasmic Antibodies Directed against Proteinase 3 and Myeloperoxidase Clin. Chem., October 1, 2000; 46(10): 1717 - 1719. [Full Text] [PDF] |
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