The manufacturer used 50 IF-ANA-positive and 30 IF-ANA-negative sera to verify that the COBAS-ANA detects only the disease-specific ANAs and does not react against the control sera, but its clinical usefulness has not been evaluated.
We also compared the ability of the COBAS-ANA and IF-ANA to detect the eight disease-specific ANAs. When the positivity (sensitivity for detection of disease-specific ANAs) of the COBAS-ANA was determined in CTD patients who were positive for at least one of eight disease-specific ANAs, the positivity was 91.8% at a cutoff index of 0.9, but rose to 97.1% at a cutoff index of 0.6, which was almost the same as the 97.6% positivity for the IF-ANA at cutoff dilution of 1:40.
Comparison of the COBAS-ANA and the IF-ANA for measurement of ANAs in patients with CTD.
Four of these patients were positive for at least one disease-specific ANA, including one patient with RA who was positive for both anti-SSA/Ro and anti-dsDNA antibodies.
Laboratories must make a great effort to follow these recommendations and to keep their ANA data reliable and accurate.
Two types of EIA-based ANA screening tests are commercially available at present (6, 8).
This is an advantage for the COBAS-ANA because the ANA test is frequently requested to screen CTD patients (excluding patients with RA) from patients with RA and soft tissue rheumatism.
(18), the AUC for an EIA-based ANA was not significantly different from that for an IF-ANA.
In a study by Roche Diagnostics to evaluate time consumption and costs for ANA testing, the total costs per determination for the COBAS-ANA were calculated to be 7.04-7.26 DM (US $3.03-3.12), whereas those for the IF-ANA were 5.54-5.57 DM (US $2.38-2.40; Roche Diagnostics, unpublished data).
The COBAS-ANA cannot tell the ANA staining pattern and may not detect some important antibodies to nuclear antigens, such as proliferating cell nuclear antigens and nucleolar antigens, that can be easily detected by the IF-ANA.
Hans-Peter Lehmann, David Panneton, and Syuichi Hayashi (Roche Diagnostics), Hiroshi Suno (MBL), and Tomoyoshi Terakawa (DIA-IATRON) for providing the ANA reagent sets and for helpful discussions.
Multicenter evaluation study on a new HEp2 ANA screening enzyme Immune assay.