29th January 2024

Diagnosis

If GCA is highly suspected, it is crucial not to delay the initiation of high-dose glucocorticoids to minimise the risk of vision loss. Initial laboratory tests such as low red cell count and raised ESR and CRP can be suggestive of the disease. 

Doppler ultrasound of the temporal arteries is the first line imaging technique for suspected GCA. Oedema and thickening of the vessel wall (halo sign), non-compressible artery (compression sign) and stenosis and occlusion of the vessels are all supportive of the diagnosis. However, this is operator-dependent, and other modalities such as high-resolution MRI, MRA, CTA, and PET scans can also be used. 

The gold standard for diagnosis is a temporal artery biopsy. Typical findings include panarteritis, proliferation of the intima and subsequent stenosis of the artery, necrosis of the media, and mononuclear infiltration of the vessel wall with formation of the giant cells. Despite this, histopathology may be falsely negative due to skip lesions and biopsy of the contralateral temporal artery may be required. 

Patients with PMR with no symptoms of GCA above the neck can be diagnosed clinically without a temporal artery biopsy.