Table 1 Sensitivity and specificity as diagnostic indicators for rheumatoid arthritis for antibodies against cyclic citrullinated peptide (anti-CCP Ab) and for rheumatoid factor (RF) of IgA, IgM, and IgG isotypes, in combination with the presence of a shared epitope (SE) allele – HLA-DRB1*0401 or B1*0404 – in 59 'prepatients' whose blood samples antedated the appearance of symptoms of rheumatoid arthritis (median 2.0 years [interquartile range 0.9–3.9]) and in 118 matched controls.
Variables | Sensitivity | Specificity | ||
|---|---|---|---|---|
% | 95%CI | % | 95%CI | |
Anti-CCP Ab | 37 | 25–51 | 98 | 93–100 |
IgA-RF | 42 | 29–56 | 94 | 87–98 |
IgM-RF | 22 | 12–35 | 94 | 87–98 |
IgG-RF | 17 | 8–30 | 94 | 87–98 |
SE (B1*0404 or 0401)1 | 60 | 45–72 | 64 | 54–73 |
SE + anti-CCP Ab | 28 | 17–42 | 99 | 94–100 |
SE + IgA-RF | 25 | 14–38 | 98 | 93–100 |
SE + IgM-RF | 14 | 6–27 | 98 | 93–100 |
SE + IgG-RF | 11 | 4–22 | 99 | 94–100 |
SESE (B1*0404 or 0401)1 | 28 | 17–42 | 95 | 88–98 |
SESE + anti-CCP Ab | 14 | 6–27 | 99 | 94–100 |
SESE + IgA-RF | 7 | 2–18 | 99 | 94–100 |
SESE + IgM-RF | 5 | 1–16 | 99 | 94–100 |
SESE + IgG-RF | 4 | 0–14 | 100 | 95–100 |