medwireNews: The authors of a systematic review and meta-analysis have identified a number of clinical and laboratory features that should be assessed when investigating patients with suspected giant cell arteritis (GCA).
However, Kornelis van der Geest (University Medical Center Groningen, the Netherlands) and colleagues stress that “[n]o single symptom, physical sign, or laboratory test is sufficient to completely rule in or rule out GCA,” and “additional investigations (vascular imaging and/or temporal artery biopsy) are required” for a definitive diagnosis.
The meta-analysis included 68 studies comprising a total of 14,037 individuals with suspected GCA, 4277 of whom were diagnosed with the disease.
van der Geest et al report in JAMA Internal Medicine that two symptoms – limb claudication and jaw claudication – were significantly associated with a positive diagnosis of GCA, with positive likelihood ratios (LRs) of 6.01 and 4.90, respectively.
A number of physical and funduscopic abnormalities were also significantly associated with a positive diagnosis, including any temporal artery abnormality (LR=2.29), a number of specific temporal artery abnormalities (thickening, loss of pulse, and tenderness; LR=3.14–4.70), and anterior ischemic optic neuropathy (LR=2.15).
Of the laboratory features, erythrocyte sedimentation rates (ESR) of more than 60, 80, or 100 mm/h were all significantly associated with GCA diagnosis (LR=2.40–3.11), as was a platelet count of more than 400 × 103/μL (LR=3.75).
Conversely, the researchers also identified features “that should downgrade the level of suspicion for GCA,” including age of 70 years or younger, ESR of no more than 40, 50, or 60 mm/h, and a C-reactive protein level below 2.5 mg/dL.
Although “no single feature is likely to shift pretest probability sufficiently to render further investigation for GCA unnecessary,” these findings “may inform clinical decisions, including selection and timing of investigations, and whether to immediately commence high-dose glucocorticoid therapy or await further test results,” writes the team.
van der Geest and colleagues also say that “some features considered classic for GCA, such as headache, scalp tenderness, and constitutional symptoms, have limited use for upgrading or downgrading the clinical probability of GCA” based on a lack of significant associations between these features and definitive diagnosis in their meta-analysis.
“This does not mean, however, that these symptoms are irrelevant,” they add.
“Our meta-analysis shows that the prevalence of these classic features is high among patients with and without GCA, suggesting that the diagnostic value of these symptoms may have been used up earlier in the care pathway.”
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