Labial Salivary Gland Biopsy: Inter-rater Reliability and Clinical Correlations

Objectives: For many years, the labial salivary gland (LSG) biopsy has been considered the “gold standard” in confirming a diagnosis of Sjögren's syndrome (SS). Recently, the accuracy of interpretation and diagnostic benefits of this procedure have been reviewed with mixed findings. One objective of this study was to assess the inter-rater agreement among five pathologists who provided independent assessments of labial salivary gland biopsies. A second objective was to assess the relationship between biopsy findings and clinical disease parameters.

Methods: Three oral pathologists and two head/neck medical surgical pathologists, blinded to clinical measures, provided independent histopathological diagnosis and focus scores for 37 patients who had undergone lip biopsies for sicca symptoms. Diagnoses were scored as either consistent with Sjögren's syndrome or chronic sialadenitis. Focus scores for SS ranged from 0 to 12. Inter-rater reliability was assessed using both the percentage of overall agreement and the intraclass correlation coefficient (ICC). Relationships between biopsy diagnoses and clinical disease parameters were examined using nonparametric correlation analysis.

Results: Overall agreement among the five pathologists was poor for both ratings of focus scores (agreement =52.1%; ICC=0.48) and diagnoses (agreement=79.5%, ICC=0.60), although agreement within-specialty was quite good; percent agreement for diagnostic status was 89% for oral pathologists and 100% for surgical pathologists. Correlations between ANA titer and ratings of both focus score and diagnostic status were statistically significant for all five pathologists. However, the ratings of oral pathologists were most highly correlated with serological measures (anti-SSA, anti-SSB, ESR), while those of surgical pathologists were most highly correlated with salivary flow rate and disease damage.

Conclusion: Because the labial salivary gland biopsy provides valuable information in most clinical situations, inconsistencies in its interpretation need to be addressed.

Acknowledgement: This project was supported by the UFCD Center for Orphaned Autoimmune Disorders (COAD).