Should a temporal artery biopsy (TAB) or a PET-CT scan of the head and neck be performed first to evaluate for giant cell arteritis (GCA) or other large vessel vasculitis in this patient?

From the Guidelines

For a patient being evaluated for giant cell arteritis (GCA) or large vessel vasculitis, a temporal artery biopsy (TAB) should generally be performed first before a PET-CT scan. This approach is based on the recommendations from the 2021 American College of Rheumatology/Vasculitis Foundation guideline for the management of giant cell arteritis and Takayasu arteritis 1. TAB remains the gold standard diagnostic test for GCA with high specificity, and it should be performed within 1-2 weeks of starting corticosteroid therapy to minimize false-negative results. The procedure involves removing a 2-3 cm segment of the temporal artery under local anesthesia, with bilateral biopsies sometimes recommended to increase diagnostic yield.

Key Considerations

• TAB is preferred initially because it is more specific, less expensive, involves less radiation exposure, and has been the established diagnostic standard for longer.
• While PET-CT is valuable for detecting large vessel involvement and can identify inflammation in vessels not accessible to biopsy, it should typically be used as a complementary test after TAB or when TAB results are negative but clinical suspicion remains high.
• In cases where cranial symptoms are absent and there is suspicion for isolated large vessel vasculitis, or when TAB is contraindicated or technically challenging, PET-CT might be considered as the initial diagnostic test.

Diagnostic Approach

• The patient's presentation, including subacute infarction of the left parieto-occipital region, 90% stenosis of the left subclavian artery, weight loss, non-specific left-sided headaches, and left jaw discomfort, along with elevated hemoglobin, hematocrit, and platelet count, suggests a possible diagnosis of GCA or large vessel vasculitis.
• Given the patient's symptoms and the need for a definitive diagnosis, TAB is the recommended initial diagnostic test, as it provides a high degree of specificity for GCA.
• If the TAB results are negative but clinical suspicion remains high, or if TAB is contraindicated or technically challenging, PET-CT may be considered as a complementary diagnostic test to evaluate for large vessel involvement.

Evidence-Based Recommendations

• The 2021 American College of Rheumatology/Vasculitis Foundation guideline recommends TAB as the initial diagnostic test for suspected GCA, with PET-CT used as a complementary test in certain cases 1.
• The guideline also recommends that TAB be performed within 1-2 weeks of starting corticosteroid therapy to minimize false-negative results.
• The use of PET-CT in the diagnosis of GCA and large vessel vasculitis is supported by studies demonstrating its high sensitivity and specificity for detecting vascular inflammation 1.

From the Research

Diagnostic Approach for Giant Cell Arteritis (GCA)

The patient's presentation of subacute infarction in the left parieto-occipital region, 90% stenosis of the left subclavian artery, weight loss, non-specific left-sided headaches, and left jaw discomfort, along with transient vision loss and lower quadrantopsia, suggests a possible diagnosis of giant cell arteritis (GCA) or other large vessel vasculitis.

Temporal Artery Biopsy (TAB) vs. PET-CT Scan

When considering whether to perform a temporal artery biopsy (TAB) or a PET-CT scan of the head and neck first, several factors come into play:

• TAB Sensitivity and Specificity: Studies have shown that TAB has a high specificity for GCA but variable sensitivity, which can be influenced by factors such as the length of the biopsy specimen and the timing of corticosteroid treatment 2, 3, 4.
• Clinical Utility of TAB: Research indicates that TAB may not be necessary in all cases of suspected GCA, especially when clinical suspicion is low or when patients do not meet specific diagnostic criteria 5, 6.
• Non-invasive Imaging: The use of non-invasive vascular imaging technologies like PET-CT can provide valuable information on large vessel involvement and may help in diagnosing GCA or other vasculitides, potentially reducing the need for TAB in some cases 4.

Decision Making

Given the patient's symptoms and the need for a definitive diagnosis, the following points should be considered:

• TAB: It is a diagnostic gold standard for GCA but has limitations, including false negatives and the invasive nature of the procedure 2, 4.
• PET-CT Scan: This can be a useful tool for assessing large vessel vasculitis and may guide the decision to perform a TAB or initiate treatment based on clinical suspicion and imaging findings 4.

Recommendations

Based on the evidence:

• A careful selection of patients for TAB is recommended, considering factors such as clinical presentation, laboratory findings, and the potential for alternative diagnoses 2, 6.
• Non-invasive imaging, including PET-CT, may play a role in the diagnostic workup, especially for evaluating large vessel involvement and guiding further management 4.
• The decision to perform a TAB or a PET-CT scan first should be based on individual patient factors, including the severity of symptoms, the presence of specific clinical findings suggestive of GCA, and the availability of diagnostic resources 5, 3, 4.