What tests should be performed in the case of suspected giant cell arteritis (GCA)? What should we look for in the physical examination, laboratory tests, and imaging studies?
Bhaskar Dasgupta: First of all, in patients with GCA, we need to make sure that they do have GCA. We look at the pulses, and not only at the temporal artery pulses and the branches, but also at the peripheral pulses: whether the pulses are present, whether the arteries are thickened. Also sometimes when the arteries are involved in inflammation, they become tender, so the carotids can become tender. It is called carotidynia. So you look at the pulses, look for any ischemia that the patient might have. We also look at features of polymyalgia: the patients will have difficulty lifting their arms up or will have tenderness in their arms. We also need to exclude other conditions because GCA is associated with inflammatory response, and there are other conditions, like infections, tumors of the base of the skull, which can actually present like GCA. So you want to make sure that the patient does not have any other infective, any other neoplastic, or any other inflammatory problem which may look like GCA.
There is a lot of examination that needs to be done. We need to look at the cranial nerves. Sometimes in GCA you can have involvement of the oculomotor nerves, so you need to look at that very carefully. All those investigations have to be done, and then you arrive at the question, “Is this a low probability of GCA, is this a high probability of GCA, or is this an intermediate probability of GCA?” Then you choose your tests that you have at your disposal. For example, if you are an expert in ultrasound and you have a good machine that gives you good results, then you do an ultrasound first. Why should we do the ultrasound first? Because it is a noninvasive test and it is a point-of-care test. So, you do the clinical examination and then you do the ultrasound examination.
If someone has a high probability of GCA and you do an ultrasound and find the typical halo [sign], you do not need to do anything else, you just start treatment with the patient. In the patient who has got a low probability of GCA, you do an ultrasound, and the ultrasound is negative, that is it. You say, “You do not have GCA,” and you look for something else. In the low-probability situation, if ultrasound is positive, you may want to do another test because in someone who has a low probability of GCA, you do not just want to start treatment with steroids because the ultrasound is positive. So, you may want to do a temporal artery biopsy. In several situations, you may want to do a second test: when the diagnosis is not very clear-cut or your test result is doubtful, you may want to do a temporal artery biopsy or you may want to do some other scan, like a positron emission tomography computed tomography (PET-CT) or magnetic resonance imaging (MRI), particularly if there is a feature of large-vessel GCA.
That is the general approach that we are advocating in patients with suspected GCA. First, stratify the probability as low, intermediate, or high, then choose your test. Usually it is ultrasound, but you may have to use other backup tests.