Epidermal Fatty Acid-Binding Protein: A Novel Marker in the Diagnosis of Dry Eye Disease in Sjögren Syndrome

Abstract

Purpose: Sjögren syndrome (SS) is a chronic inflammatory autoimmune disease of the lacrimal and salivary glands. This study compared the concentrations of epidermal fatty-acid binding protein (E-FABP) in the saliva, serum, and tears of SS patients with dry eye and dry mouth, with those of healthy adults to investigate the usefulness of E-FABP as a diagnostic marker for SS.

Design: Prospective, observational case series.

Participants: The subjects were 11 new patients with untreated Sjogren syndrome and 12 healthy control individuals.

Methods: The diagnosis of SS was in accordance with the Ministry of Health, Labour and Welfare (Japan) Diagnostic Criteria (1999). Saliva, serum, and tear specimens were collected during internal medicine, dental, and ophthalmological examinations. The ophthalmological tests included the Dry Eye-related Quality of life Score (DEQS), tear break-up time (BUT), vital staining with fluorescein (FS) and lissamine green (LG), and the Schirmer test-1. The E-FABP concentration in the tears, saliva, and serum was measured by enzyme-linked immunosorbent assay (ELISA).

Main outcome measure: The E-FABP concentrations were compared between patients and controls.

Results: There were significant differences between the patient and healthy control groups in all ophthalmological test results. There were no significant differences between the groups in the E-FABP concentrations in the saliva (p = 0.1513) or the serum (p = 0.4799), but the E-FABP concentration in the tears significantly differed between groups. The E-FABP concentration in tears tended to be significantly lower in patients with SS (mean, 323.5 ± 325.6 pg/mL) than healthy control subjects (mean, 4076 pg/mL; p = 0.0136). The E-FABP concentration in tears significantly correlated with the results of dry eye parameters.

Conclusion: The E-FABP concentration in tears appears to be related to ocular surface epithelial damage and tear stability and may be a promising novel biomarker in the diagnosis of SS.

Keywords: dry eye; epidermal fatty-acid binding protein (E-FABP), Sjögren’s syndrome; tears.

Figure 1

Tear E-FABP concentrations. E-FABP concentration in tears was 323.5 ± 325.6 pg/mL (range: 28.08–710.5 pg/mL; median: 169.1 pg/mL)in the patient group (n = 5) and 4076 ± 5746 pg/mL (range: 106.3–18516 pg/mL; median: 1629 pg/mL) in the control group (n = 12); the difference between the groups was statistically significant (p = 0.0136). Data are expressed as the mean with SD (one bar per column).

Figure 2

Saliva E-FABP concentrations. The E-FABP concentration in the saliva was 46.46 ± 38.22 pg/mL (range: 8.527–130.6 pg/mL; median: 40.44 pg/mL) in the patient group (n = 9) and 32.08 ± 38.31 pg/mL (range: 6.1–107.3 pg/mL; median: 20.38 pg/mL) in the control group (n = 12); the difference between the groups was not statistically significant (p = 0.1513). Data are expressed as the mean with SD (one bar per column).

Figure 3

Serum E-FABP concentrations. The E-FABP concentration in the serum was 1630 ± 1030 pg/mL (range: 95.94–3420 pg/mL; median: 1545pg/mL) in the patient group (n = 11) and 1604 ± 1686 pg/mL (range: 350.4–6774 pg/mL; median: 1074pg/mL) in the control group (n = 12); the difference between the groups was not statistically significant (p = 0.4799). Data are expressed as the mean with SD (one bar per column).

Figure 4

Correlation between tear E-FABP concentrations and DED parameters. X and Y axis units: FABP: pg/mL; DEQS: points (pts); BUT: seconds (sec); Schirmer: millimeters (mm); FS: points (pts); LG: points (pts).