Sensitivity and specificity of immunological methods for the detection of anti-topoisomerase I (Scl70) autoantibodies: results of a multicenter study. The Italian Society of Laboratory Medicine Study Group on the Diagnosis of Autoimmune diseases.
BACKGROUND
The ability of immunometric methods to identify anti-topoisomerase I (Scl70) antibodies is controversial. We wished to quantify the performance of the currently available commercial systems for the assay of anti-topoisomerase I antibodies in a large multicenter study.


METHODS
Fifty Italian clinical laboratories analyzed 36 serum samples: 27 from individuals with scleroderma/systemic sclerosis, and 9 from a control group. The scleroderma/systemic sclerosis samples were positive in our laboratories by both ELISA and immunoblot (IB), and the control samples were negative. The laboratories used 42 immunoenzymatic (ELISA), 21 IB, 3 counterimmunoelectrophoresis, and 2 dot-blot methods, produced by 23 different manufacturers.


RESULTS
We obtained 2389 results. The ELISA methods showed 99.2% specificity and 97.2% sensitivity for detection of anti-Scl70 antibodies. For IB methods, specificity was 97.6% and sensitivity was 96.1%. The Western-blot method had poor analytical specificity (27% false positives for anti-extractable nuclear antigen antibodies other than anti-Scl70).


CONCLUSIONS
Excluding Western blots, commercial ELISA and IB reagents as used in clinical laboratories have a sensitivity and a specificity >95% for determination of anti-Scl70 antibodies.
Bizzaro
N
N
Laboratorio di Patologia Clinica, Ospedale Civile, 30027 S. Donà di Piave (VE), Italy. nbizzaro@dacos.it
Tonutti
E
E
Villalta
D
D
Bassetti
D
D
Tozzoli
R
R
Manoni
F
F
Pirrone
S
S
Piazza
A
A
Rizzotti
P
P
Pradella
M
M
D001323:Autoantibodies / Q000097:blood*; D015153:Blotting, Western; D004264:DNA Topoisomerases, Type I / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D015151:Immunoblotting; D007122:Immunoelectrophoresis; D011933:Reagent Kits, Diagnostic; D015203:Reproducibility of Results; D012595:Scleroderma, Systemic / Q000276:immunology; D012680:Sensitivity and Specificity
D001323:Autoantibodies; D011933:Reagent Kits, Diagnostic; D004264:DNA Topoisomerases, Type I