Which lab test should a nurse practitioner order when the suspected diagnosis is temporal arteritis?

When temporal arteritis, also known as giant cell arteritis, is suspected, ordering an erythrocyte sedimentation rate (ESR) is critical. The ESR test measures the rate at which red blood cells settle at the bottom of a test tube in one hour. An elevated ESR indicates inflammation in the body, which is commonly associated with temporal arteritis due to the inflammation of the temporal arteries. High levels of ESR can thus help support the diagnosis, prompting further investigation or management.

While other tests, such as a complete blood count, may provide supportive information (like anemia or thrombocytosis), they are not as directly indicative of the inflammatory process characteristic of temporal arteritis. Antinuclear antibody testing is more specific for autoimmune conditions rather than directly diagnosing a cranial vasculitis. An electrolyte profile does not play a role in diagnosing temporal arteritis, as it primarily assesses electrolyte imbalances rather than inflammation. Therefore, the ESR is the most relevant and useful test to confirm the presence of significant inflammation associated with this condition.