Table 1.

Activity of Cathepsin S and concentrations of secretory IgA (sIgA), Lactoferrin (LF), and Cystatin C in patients compared between diagnostic groups, n = 312 eyes, 156 subjects.

	SS* (n = 33)	RA (n = 33)	Other (n = 31)	Dry Eye (n = 35)	Healthy (n = 24)
Age years (Mean ± SE)	55.8 ± 2.4	54.5 ± 2.4	49.0 ± 2.5	65.4 ± 2.3	45.7 ± 2.5
p	—	0.70#	0.10#	0.02#	0.02#
CTSS RFU/protein** (Med ± SE)	5631 ± 937.9	1020 ± 205.5	786 ± 136.1	912.1 ± 399.2	267 ± 74.6
p	—	<0.0001†	<0.0001†	<0.0001† 0.003††	<0.0001†
Cys C ng/protein** (Med ± SE)	211.7 ± 60.16	788.8 ± 121.3	1123 ± 117.5	834.2 ± 81.56	1490 ± 106.0
P	—	< 0.0001†	<0.0001†	0.0002†	<0.0001†
sIgA µg/protein** (Med ± SE)	224 ± 97.0	1348 ± 147.0	1106 ± 163.2	1982 ± 152.6	1452 ± 121.9
p	—	<0.0001†	<0.0001†	<0.0001†	<0.0001†
LF µg/protein** (Med ± SE)	207.1 ± 53.7	1031 ± 97.45	1428 ± 118.7	2018 ± 193.2	1572 ± 86.6
p	—	<0.0001†	<0.0001†	<0.0001†	<0.0001†

All data were normalized to the total protein concentration of the tear sample.

Groups were compared using generalized estimating equations to account for correlation between the eyes of each subject.

Within-subject correlation (between eyes) for comparison between SS, RA, OAD and healthy, CTSS r = 0.56; sIgA r = 0.74; LF r = 0.61; Cys C r = 0.62.

All models adjusted for age: p-value for association with age: CTSS p = 0.0005; sIgA p = 0.74; lactoferrin p = 0.86; cystatin C p = 0.98.

Overall p-value for group differences: CTSS p < 0.0001; sIgA p < 0.0001; LF p < 0.0001; Cys C p < 0.0001.

^*Primary and secondary Sjögren’s syndrome combined.

^**Indicates per 10 mg of total tear protein.

^# Overall p-value for group differences by ANOVA < 0.0001. P-values for difference from SS adjusted for multiple comparisons using Hochberg method.

^†Statistical analysis is based on log transformed values, p is for comparison with SS.

^††Statistical analysis is based on log transformed values, p is for comparison with Healthy.

SS = Sjögren’s Syndrome, RA = Rheumatoid Arthritis, Other = autoimmune disease other than SS or RA.