Development of the Takayasu's arteritis integrated disease activity index

Abstract

Background: Accurate clinical assessment of disease activity in Takayasu’s arteritis (TAK) can be challenging. 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) can directly measure vascular inflammation. This study details the development of a new type of disease activity index called the Takayasu’s Arteritis Integrated Disease Activity Index (TAIDAI). Methods: Clinical symptoms for TAIDAI were identified from a literature review. Each symptom was paired to FDG-PET findings in corresponding arterial territories. Constitutional symptoms were paired with acute phase reactant levels. One point was given for each clinical symptom paired with supporting FDG-PET or laboratory abnormalities and summed into the TAIDAI score. A TAIDAI of ≥1 defined active disease. To assess performance of TAIDAI, face validity, content validity and sensitivity to change were evaluated within a prospective observational cohort of patients with TAK. Results: Seventeen clinical symptoms were paired to imaging or laboratory abnormalities. In a cohort of 96 patients contributing 204 study visits, TAIDAI showed excellent sensitivity (96.3%) and good specificity (79.2%) compared to physician’s clinical assessment. TAIDAI significantly correlated with physician global assessment, PET Vascular Activity Score (PETVAS), patient global assessment, and acute phase reactant levels. In patients treated with either TNF inhibitors or tocilizumab, a TAIDAI of 0 was achieved in 21 of 23 (91%) patients who met a pre-defined definition of clinical response.