No single sign, symptom adequate 'to rule in or rule out' giant cell arteritis
Although no single sign or symptom alone is strong enough to confirm a diagnosis of giant cell arteritis, a collection of features, including limb claudication and temporal artery thickening, are most informative, according to findings published in JAMA Internal Medicine.
“Making a diagnosis of giant cell arteritis (GCA) can be challenging,” Kornelis S. M. van der Geest, MD, PhD, of the University of Groningen, in the Netherlands, told Healio Rheumatology. “Prompt diagnostic evaluation and treatment are needed due to the substantial risk of ischemic sight loss. The EULAR recommendations and British Society for Rheumatology guidelines for GCA recommend selecting diagnostic tests for GCA based on the clinical probability of the disease. Clinicians may wonder how such clinical probability should be estimated.”
To examine the diagnostic accuracy of various symptoms, signs and laboratory tests for GCA, van der Geest and colleagues conducted a systemic review and meta-analysis of trials and observational studies describing patients who were suspected of having the disease. The researchers searched data using PubMed, EMBASE and the Cochrane Database of Systematic Reviews, including findings published from November 1940 through April 5, 2020.
Using an appropriate reference standard for GCA — temporal artery biopsy, imaging test, or clinical diagnosis — and with available data for at least 1 symptom, physical sign, or laboratory test, the researchers identified and included 68 unique studies, representing 14,037 patients. Data extraction included screening, full text review and quality assessment, as well as a bivariate model for the diagnostic test meta-analysis. The primary outcome measures were diagnostic accuracy parameters, including positive and negative likelihood ratios (LR).
According to the researchers, findings associated with a confirmed GCA diagnosis include limb claudication (positive LR = 6.01; 95% CI, 1.38-26.16), jaw claudication (positive LR = 4.9; 95% CI, 3.74-6.41), temporal artery thickening (positive LR = 4.7; 95% CI, 2.65-8.33), temporal artery loss of pulse (positive LR = 3.25; 95% CI, 2.49-4.23), a platelet count greater than 400×103/L (positive LR = 3.75; 95% CI, 2.12-6.64), temporal tenderness (positive LR = 3.14; 95% CI, 1.14-8.65) and an erythrocyte sedimentation rate greater than 100 mm/h (positive LR = 3.11; 95% CI, 1.43-6.78).
Meanwhile, findings that eliminated a diagnosis of GCA included the absence of an erythrocyte sedimentation rate greater than 40 mm/h (negative LR = 0.18; 95% CI, 0.08-0.44), the absence of a C-reactive protein level of 2.5 mg/dL or more (negative LR = 0.38; 95% CI, 0.25-0.59) and being aged 70 years or younger (negative LR = 0.48; 95% CI, 0.27-0.86).
“No single clinical or laboratory feature is sufficient to rule in or rule out GCA,” van der Geest said. “Classic features of GCA such as headache and scalp tenderness show a high prevalence among patients with GCA. However, these symptoms have limited use for upgrading or downgrading the clinical probability of GCA. In the diagnostic cohort studies, many patients without GCA also had classic symptoms of GCA. The classic symptoms seem to prompt the initial suspicion of GCA and onward referral to a specialist; thus, their diagnostic value is used up early in the diagnostic pathway.”
“Our study may help clinicians judge the clinical probability of giant cell arteritis based on evidence from 68 diagnostic cohort studies,” he added. “Since no single clinical or laboratory feature is sufficient to rule in or rule out the disease, additional investigations such as vascular imaging and/or temporal artery biopsy are required.”