Indirect immunofluorescence on HEp-2000 substrate is a sensitive method for detecting anti-Ro/SSA antibodies in patients with lupus erythematosus and/or photosensitivity

### Objective To evaluate the sensitivity of indirect immunofluorescence (IIF) utilizing HEp-2000 cells to detect antinuclear and anti-Ro/SSA antibodies. ### Methods We examined 5949 sera samples from 2316 patients with connective tissue diseases. All sera were tested by IIF on HEp-2 cells as substrate and by counterimmunoelectrophoresis (CIE). The positive sera for anti-Ro/SSA antibodies by CIE were retested by IIF using HEp-2000 cells. The sera that were anti-Ro/SSA-positive in CIE but negative on HEp-2000 cells were tested by ELISA for the 60 and 52 subunits of Ro/SSA antigen. ### Results Our results confirm the high sensitivity (81%) of HEp-2000 cells in detecting anti Ro/SSA antibodies. ### Conclusion Using the HEp-2000 substrate is a reliable, simple alternative method for detecting anti-Ro/SSA antibodies in a first-level screening test such as IIF, especially in patients with lupus erythematosus and/or photosensitivity.