Standardization of minor salivary gland biopsy interpretation in Sjögren’s disease: using the 2017 EULAR recommendations: a monocentric study

OBJECTIVES: To assess the inter- and intrarater reliability of minor salivary gland biopsy (MSGB) interpretation for the evaluation of Sjögren's disease (SjD), in accordance with the 2017 EULAR recommendations. METHODS: The reproducibility of MSGB findings in patients with suspected SjD was analysed by two pathologists. For intrarater reliability, expert examiner A (ExA) evaluated 196 slides twice, with a two-month interval, following a standardised blinded protocol. For Inter-rater reliability, ExA's initial assessment was compared with that of the routine service pathologists (ExR) and with expert examiner B (ExB), who independently evaluated a random subset of 115 slides. Agreement for qualitative variables was assessed using Cohen's kappa coefficient (κ), and the intraclass correlation coefficient (ICC) was calculated for quantitative measures. RESULTS: Inter- and intrarater analyses demonstrated substancial to almost perfect agreement (κ ≥ 0.6) for glandular area, dichotomised focus score (FS ≥ 1 or < 1), and the diagnosis of focal lymphocytic sialadenitis (FLS). In contrast, agreement for structural damage assessment was only moderate to fair (κ ≤ 0.4) across both analyses. The ICC for FS indicated good reliability (≥ 0.61) between ExR and ExA, and almost perfect reliability (ICC≥ 0.76) between ExA and ExB, as well as within ExA's intrarater comparison. CONCLUSION: Inter- and intrarater reliability for diagnosing FLS and determining FS is good, whereas reliability for grading structural damage remains limited. This discrepancy may reflect less consistent training and criteria for assessing tissue damage compared with inflammatory features. Improving MSGB reproducibility will require stronger standardisation of histopathological procedures and enhanced pathologist training.