What is it about?
Giant cell arteritis is the most common systemic vasculitis in the elderly and can cause irreversible blindness, and occasionally myocardial infarction, aortitis, stroke or even death. Temporal artery biopsy remains the criterion standard test for giant cell arteritis, but is a time-consuming and invasive test. Our multivariable (not multivariate) prediction model estimates the patient's risk of giant cell arteritis prior to temporal artery biopsy. The online spreadsheet calculator allows for risk stratification. https://docs.google.com/spreadsheets/d/1wlRFGleW2Vf-LlylmY76KSTzIAf1TrX5U_1770HhD1Y/edit#gid=0
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Why is it important?
The calculator facilitates objective decision-making in the management of patients with suspected giant cell arteritis. In the prediction model the patient variables are age, gender, new onset headache, temporal artery tenderness or pulselessness, jaw claudication, vision loss and diplopia. The bloodwork variables are the pre-steroid ESR, CRP and platelet level. In the future, using the prediction rule in conjunction with tests such as temporal artery ultrasound or dynamic contour tonometry may enhance the utility of non-invasive alternatives to temporal artery biopsy.
Perspectives
This article is the collaborative effort of physicians from 7 different medical institutions and is derived from both ophthalmology and rheumatology patients. As such it is generalizable to most patients. Misclassification errors are still a problem, as with any prediction algorithm. Notwithstanding, the calculator objectifies decision-making when discussing management options with patients with suspected GCA. The calculator only predicts biopsy-proven GCA. Interpret the probability score with respect to the cutpoints. For scores lower than 15%, ask your patient, "Given GCA is a potentially blinding disease, and there is a _% chance you might have GCA, do you want to proceed with TABx and steroids, or do you want to continue observation?" None of the 133 biopsy-proven GCA patients had a probability score below 2.7% 7.5% of the patients with biopsy proven GCA had normal platelet, and normal ESR and normal CRP level pre-steroid; the average probability score on this seronegative group was 11%. Female gender and diplopia were NOT helpful predictors of GCA in this study. On the calculator, you will see the risk goes down for females and patients with diplopia. More females had GCA than males, but more females also had negative biopsy. In this series 35% with biopsy proven GCA had vision loss. Perhaps the high incidence of vision loss made binocular diplopia unlikely and that is why the diplopia variable performs this way on the calculator.
Dr Edsel B Ing
University of Toronto
Read the Original
This page is a summary of: Multivariate prediction model for suspected giant cell arteritis: development and validation, Clinical Ophthalmology, November 2017, Dove Medical Press,
DOI: 10.2147/opth.s151385.
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