Characteristics of patients who were ANA positive in all assays and patients who showed discordance between assays
| ANA positive all assays | Disagreement among assays | P value | |
| Age (years)* | 34.2 (20.2–67) | 38.4 (21.6–62.5) | NS† |
| Duration of SLE (years)* | 6.3 (0.1–33.4) | 5.7 (1.6–19.8) | NS |
| Male (%) | 6.3% male | 11.4% male | NS‡ |
| Caucasian (%) | 56% | 66% | NS‡ |
| African American (%) | 38% | 31% | NS‡ |
| Lupus nephritis (%) | 67% | 51% | NS‡ |
| Ever anti-dsDNA positive | 59% | 23% | 0.0006‡ |
| C3§ (SD) | 99 (32) | 121 (34) | 0.0058¶ |
*Median (range).
†Mann-Whitney test.
‡Fisher’s exact test.
§Complement component C3, measured in a serum sample taken at the same time the sample for ANA was obtained.
¶Unpaired t test.
ANA, antinuclear antibody; ds-DNA, double-stranded DNA; SLE, systemic lupus erythematosus.