Purpose
Traditional autoantibodies used in the diagnosis of Sjögren's syndrome (SS) include SS-A (anti-Ro), SS-B (anti-La), rheumatoid factor (RF), and anti-nuclear antibody (ANA). The usefulness of these antibodies is limited by low specificity and sensitivity, particularly at early stages of the disease. Three novel autoantibodies (Secretory Protein-1 (SP-1), Carbonic Anhydrase-6 (CA-6) and Parotid Secretory Protein (PSP) have been identified that may aid in early diagnosis of SS. However, patients positive for novel autoantibodies have not yet been well characterized. Therefore, we conducted a retrospective chart review to determine the prevalence of novel antibodies in dry eye patients and examined correlations with signs and symptoms of SS.
Methods
68 dry eye patients were tested with the Sjö® kit (Nicox/Immco Diagnostics, Buffalo NY) which includes detection of SS-A, SS-B, RF, ANA, SP-1, CA-6, and PSP. Data on systemic symptoms (dry mouth, arthralgias, and myalgias) and ocular surface signs (conjunctival lissamine green staining, Schirmer’s test and osmolarity) was obtained.
Results
Of the 68 patients tested with the Sjö® kit, 22 were positive for novel SS autoantibodies (32.4%) and 4 were positive for traditional autoantibodies (5.9%). The prevalence of each novel antibody individually and in combination is summarized in Table 1. CA-6 was present in 78.5% of the novel antibody (Ab) positive group. Of the novel SS Ab group, 7 out of 22 (31.8%) had a lip biopsy for SS. 2 of these lip biopsies were positive, leading to a diagnosis of SS by the American European Consensus Group (AECG) criteria. No correlation was found between the presence of novel SS antibodies and ocular surface exam findings, arthralgias, or myalgias. However, 40.9% of novel SS-A positive patients had xerostomia, compared with 23.7% of negative patients.
Conclusions
Of the three novel SS antibodies, CA-6 was the most prevalent in our population. No significant correlation between ocular surface exam signs and the presence of novel autoantibodies was found. Patients positive for novel SS antibodies were significantly more likely to complain of xerostomia than those who were negative for those antibodies. In the future, prospective studies that follow subjects who are positive for novel SS antibodies are needed to determine the value of these antibodies for detecting early SS in dry eye patients.