O18. INCORPORATING TEMPORAL ARTERY ULTRASOUND INTO A FAST-TRACK SUSPECTED GIANT CELL ARTERITIS SERVICE: AUDITING A NEW CLINICAL PATHWAY

Abstract

Background: Giant cell arteritis (GCA) is challenging to diagnose and access to timely temporal artery biopsy (TAB) is not universal. Provision of a fast-track GCA service (FTS) incorporating temporal artery duplex US (TAUSS) has been suggested to reduce the incidence of sight loss from GCA and be cost effective. TAUSS has been performed at the Freeman Hospital since 2007. In the last 3 years we have developed a FTS for suspected GCA with ophthalmology colleagues. An audit of this service was performed between January 2014 and June 2016. Methods: Data were collected from all patients reviewed in the FTS. Referrals were received from GPs, ophthalmology and general medicine. Patients were clerked and examined by the on-call rheumatology registrar within 48 hours of referral. TAUSS was performed by an experienced consultant rheumatologist on the same day and documented as positive or negative for features of GCA. Based on clinical history, examination, TAUSS and available blood tests a decision about proceeding to TAB was made at the discretion of the supervising consultant rheumatologist or ophthalmologist. Data were collected on initial steroid dose and duration, TAUSS and TAB results and final clinician diagnosis. Results: 226 patients were seen during the 30 month audit period. GCA was diagnosed in 76 (35.9%). 212 patients (94%) had TAUSS, 42 were positive, 164 negative, 6 missing. 94 patients (44%) had a biopsy. 115 patients (including 11 with positive TAUSS) did not go onto to have a biopsy. The mean days of steroid pre-ultrasound was 2.4 and prebiopsy was 8.1. Using final diagnosis as the gold standard, the sensitivity and specificity of TAUSS were 57% and 99% respectively. The positive predictive value (PPV) of TAUSS was 95% and the negative predictive value (NPV) was 82%. Using TAB as the gold standard, the sensitivity and specificity of TAUSS were 68% and 86% respectively. The PPV was 70% and NPV was 84%. Conclusion: These data indicate that TAUSS can be incorporated into a FTS for suspected GCA and can contribute to the rapid diagnosis or exclusion of this condition. Reflecting normal clinical practice, TAUSS was used with no blinding to clinical presentation; using ultrasound and clinical judgment allowed patients with a low probability of GCA to avoid a biopsy. A small number of patients with a positive ultrasound scan did not have a biopsy, and this proportion may increase in the future with review of patient outcomes in this group. For patients who had both investigations performed, the audit shows good concordance between TAUSS and TAB. We suggest TAUSS can aid the diagnosis of GCA when performed by experienced practitioners and used alongside clinical assessment, and can reduce the need for TAB and unnecessary morbidity due to long term steroids.