Validation of a new immunoenzymatic method to detect antibodies to RNA polymerase III in systemic sclerosis.
OBJECTIVE
To test the reliability of a new enzyme-linked immunosorbent assay (ELISA) to identify anti-RNA polymerase III (RNAP III) positive sera from Italian patients with Systemic Sclerosis (SSc) and other chronic inflammatory disorders.


METHODS
A comparison between the new ELISA for anti-RNAP III and the gold standard technique, immunoprecipitation (IP), was first performed on 106 SSc patients, 16 patients with other connective tissue diseases and 10 healthy subjects. A further ELISA evaluation was performed on 224 SSc patients, 120 subjects with other rheumatic or infectious diseases, and 81 healthy controls.


RESULTS
Plotting ELISA and IP data in a Receiver Operator Characteristic curve, the ELISA cut-off value providing the best specificity (99.1%) and sensibility (100%) was 28 U/ml (AUC=0.999; p<0.0001). Using this cut-off in the second analysis, anti-RNAP III positive results were found in 41 (18.3%) SSc patients, all negative for anticentromere or anti-topoisomerase I antibodies, while only 3 subjects tested positive among the 120 sera collected from other patients. All the healthy subjects were negative.


CONCLUSIONS
This new ELISA for anti-RNAP III is highly accurate when a proper cut-off value is employed and represents a valid substitute to IP in a clinical setting.
Codullo
V
V
Division of Rheumatology, University of Pavia, and Laboratory of Clinical and Microbiological Analysis, Ospedale Civile, Latisana, Italy.
Morozzi
G
G
Bardoni
A
A
Salvini
R
R
Deleonardi
G
G
De Pità
O
O
Riccieri
V
V
Ruffatti
A
A
Tincani
A
A
Tozzoli
R
R
Valesini
G
G
Montecucco
C
C
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000906:Antibodies / Q000097:blood*; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D006801:Humans; D047468:Immunoprecipitation / Q000379:methods; D007558:Italy; D008875:Middle Aged; D012320:RNA Polymerase III / Q000276:immunology*; D012372:ROC Curve; D012016:Reference Values; D015203:Reproducibility of Results; D012595:Scleroderma, Systemic / Q000097:blood / Q000208:ethnology / Q000276:immunology*; D012680:Sensitivity and Specificity
D000906:Antibodies; D012320:RNA Polymerase III