Supplement Article |
PP4. THE DIFFICULTIES IN THE DEVELOPMENT OF HISTOLOGICAL SCORING FOR INFLAMED TEMPORAL ARTERY IN GIANT CELL ARTERITIS
1 Department of Rheumatology, Southend General Hospital, Southend on Sea, Essex, UK, 2 Sahlgrenska Hospital, Gothengberg, Sweden
Background: The major complication of GCA is vision loss. A recent audit showed a high percentage of visual loss (29%) in biopsy patients. Cytokine patterns in temporal artery biopsies (TAB) such as high interferon-gamma have reported correlation with clinical features of ischaemia. It will be useful to differential patients at higher risk for ischaemic events early, to prevent complications such as vision loss. We undertook this study to determine whether a light microscopic histological score of TAB could reliably quantify the inflammatory response and different histological patterns in GCA.
Methods: A scoring system to quantify inflammatory response in TAB was evolved from a UK-Swedish collaboration. TAB were scored as mild (1), moderate (2), Severe (3) for the following: general degree of inflammation, extent of inflammatory invasion with regard to wall layers and the circumference, presence and the extent of multinucleate giant cells, intimal thickening, fibrinous exudation and neovascularisation. Twenty five TAB from biopsy positive GCA were scored twice after a 4-week interval by a consultant histopathologist. The slides were then exchanged between the 2 centres and underwent similar review by the other histopathologist. The histopathologist were blinded to each other's scores, their own scores as well as clinical data. Intra and inter-observer reliability was assessed using kappa statistics.
Results: Intra-observer reliability showed moderate (k = 0.59, 95% CI 0.51–0.66) and good (k = 0.77, 95% CI 0.71–0.84) agreement for the two observer reliability showed poor agreement (k = 0.16, 95% CI 0.12–0.20). Of the seven parameters of inflammation only intimal thickening produced fair or better inter-observer agreement (k = 0.34, 95% CI 0.19–0.48). The agreement for giant cell infiltration was no better than would be expected by chance (k = 0.02, 95% CI –0.11 to –0.07). The table shows the percentage of TAB with moderate/severe involvement (scores 2 or 3).
Conclusion: The overall histological scores showed poor inter-observer and intra-observer reliability in GCA. Evaluation of giant cells and neo-vascularisation showed highest variability. We suggest that future histological studies agree the definitions of such abnormalities in a prior consensus training phase.
Histological score (%) with moderate/severe involvement:
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