Objectives: There are no valid instruments to measure disease activity in Takayasu arteritis (TA). We aim to provide a valid measure to assess clinical disease activity with or without incorporating acute phase reactants.
Methods: The Indian Takayasu Clinical Activity Score (ITAS) was initially derived from disease manifestations scored in the Disease Extent Index (DEI.Tak). The ITAS was validated by a group of physicians scoring both live and paper cases for inter-rater reliability (IRR), convergence with BVAS, correlation with the Physician's Global Assessment (PGA) and ESR/CRP. It was further validated at a single centre in 177 patients for its ability to discriminate between active and inactive disease state at first visit and sensitivity to change in 132 active patients measured serially at two follow-up visits. ITAS-A also included graded scores for ESR/CRP.
Results: The final ITAS2010 contains 44 items with 33 features arising from the cardiovascular system. Seven key items are weighted to score 2 and all others score 1 only. Inter-observer variability was highly satisfactory (IRR 0.97). The ITAS showed superior inter-rater agreement compared with the BVAS (IRR 0.9) and PGA (IRR 0.82). In the single-centre study, median ITAS scores at first visit were significantly higher in active disease (5.62 ± 3.14) compared with grumbling (3.36 ± 1.96) and inactive disease (1.27 ± 1.26, P < 0.0001). The therapy induced a significant decrease in the ITAS2010 but the higher ITAS-A scores remained elevated.
Conclusion: The ITAS2010, validated in over 300 TA patients and sensitive to change, is a useful measure of clinical disease activity for patient monitoring. Higher ITAS-A scores suggest poor control of active disease by current therapy.
Keywords: IRAVAS; India; Takayasu arteritis; activity index; acute phase response; large vessel disease; longitudinal studies.