Usefulness of IgA Anti-α-fodrin Antibodies in Combination with Rheumatoid Factor and/or Antinuclear Antibodies as Substitute Immunological Criterion in Sjögren Syndrome with Negative Anti-SSA/SSB Antibodies

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Figure 1.
Flow of patients through study phases.

Table 1.

Clinical and immunological features among patients with and without Sjögren syndrome (SS). Data are n (%) unless otherwise specified.

Variables	SS, n = 65	No SS, n = 149	p
Age, yrs, mean ± SD	51.8 ± 13.8	46.8 ± 15.1	0.02
Women	65 (100)	135 (90.6)	0.01
Oral symptoms	37 (56.9)	26 (17.4)	< 0.0001
Ocular symptoms	44 (67.7)	35 (23.5)	< 0.0001
Parotid enlargement	8 (12.3)	2 (1.3)	0.001
Schirmer-I test	43 (66.2)	49 (32.9)	< 0.0001
Wafer test	60 (92.3)	79 (53)	< 0.0001
Keratoconjuctivitis sicca	51/64 (79.6)	43/94 (45.7)	< 0.0001
NSWSF < 0.1 ml/min	61 (93.8)	57/122 (46.7)	< 0.0001
Focal sialadenitis	31/42 (73.8)	0/17 (0)	< 0.0001
RF	28 (43.1)	49 (32.9)	0.15
ANA ≥ 1:320	32 (49.2)	85 (57)	0.29
ANA ≥ 320 and RF	13 (20.3)	21 (11.1)	0.30
AFA-IgA	44 (67.7)	94 (63.1)	0.51
AFA-IgG	20 (30.8)	48 (32.2)	0.83
Median AFA-IgA, U/ml (range)	5.8 (4.3–48.5)	5.7 (4–48)	0.50
Median AFA-IgG, U/ml (range)	5.4 (4.3–10.9)	5.5 (4.3–17.9)	0.25
RF and AFA-IgA	22 (33.8)	35 (23.5)	0.11
ANA ≥ 1:320 plus AFA-IgA	25 (38.5)	54 (36.2)	0.75

NWSFS: nonstimulated whole salivary flow rate; RF: rheumatoid factor; ANA: antinuclear antibodies; AFA: anti-α-fodrin antibodies.

Table 2.

American College of Rheumatology (ACR) and modified immunological criterion ACR performance. Data in parentheses are 95% CI.

Immunological Criterion	SN	SP	PPV	NPV	LR+	LR−
RF + ANA ≥ 1:320	56.9 (44–69.1)	93.9 (88.8–97.2)	80.4 (66–90.6)	83.3 (76.8–88.6)	9.4 (4.8–18.3)	0.46 (0.35–0.61)
RF + AFA-IgA	61.5 (48.6–73.3)	88.5 (82.3–93.2)	70.1 (56.6–81.5)	84.0 (77.4–89.4)	5.3 (3.3–8.7)	0.43 (0.32–0.59)
AFA-IgA + ANA ≥ 1:320	64.6 (51.7–76.8)	85.9 (79.2–91.0)	66.6 (53.6–78.0)	84.7 (78.0–90.0)	4.5 (2.9–7.0)	0.41 (0.29–0.56)
RF	66.15 (53.3–77.4)	87.2 (80.8–92.1)	69.2 (56.3–80.4)	85.53 (78.9–80.4)	5.19 (3.29–8.17)	0.39 (0.27–0.55)
Two out of three of RF, ANA ≥ 1:320, or AFA-IgA	70.7 (58.1–81.4)	78.5 (71.0–84.8)	58.9 (47.2–69.9)	86.0 (78.0–91.3)	3.3 (2.3–4.6)	0.37 (0.25–0.55)

SN: sensitivity; SP: specificity; PPV: positive predictive value; NPV: negative PV; LR: likelihood ratio; RF: rheumatoid factor; ANA: antinuclear antibodies; AFA: anti-α-fodrin antibodies.