Positive LR | Negative LR | |||||
---|---|---|---|---|---|---|
ANA− | ANA+ | All | ANA− | ANA+ | All | |
Low C3/C4 | 3.3 (0.2 to 50.2) | >10.7 (0.9 to 128) | 17.0 (2.3 to 125) | 0.95 (0.83 to 1.1) | 0.73 (0.63 to 0.85) | 0.78 (0.69 to 0.89) |
High CB-CAPs | 3.3 (0.5 to 21.7) | 12.7 (1.8 to 88) | 10.8 (3.4 to 33.7) | 0.90 (0.73 to 1.1) | 0.51 (0.39 to 0.67) | 0.59 (0.48 to 0.73) |
Anti-dsDNA confirmed by IIF | 2.7 (0.2 to 35) | > 8.0 (0.7 to 97) | >6.9 (1.6 to 31.0) | 0.93 (0.82 to 1.1) | 0.80 (0.70 to 0.91) | 0.83 (0.75 to 0.92) |
CB-CAPs in MAAA | >5.7 (0.7 to 50) | >29.0 (2.4 to 355) | >24.0 (5.7 to 102) | 0.86 (0.69 to 1.1) | 0.27 (0.18 to 0.43) | 0.40 (0.30 to 0.54) |
ANA was determined using IIF and the cut-off for a positive test result was set at ≥1:40. Positive LR is calculated as sensitivity/(1- specificity). Negative LR is calculated as 1- sensitivity/(specificity). CIs (95%) are provided.
ANA, antinuclear antibodies; CB-CAP, cell bound complement activation product; dsDNA, double-stranded DNA; IIF, indirect immunofluorescence; LR, likelihood ratio; FM, fibromyalgia; MAAA, multi-analyte assay with algorithm; NA, not applicable: none of the patients ANA negative were anti-dsDNA-positive; SLE, systemic lupus erythematosus.