Should I still use both CRP and ESR when investigating temporal arteritis?

In this article

• No, CRP alone is adequate as the initial test
• References

In this article

No, CRP alone is adequate as the initial test

In a 2006 publication on ESR/CRP, bpac^nz recommended that both CRP and ESR should be tested simultaneously for patients in whom temporal arteritis was suspected.¹ However, this is no longer regarded as best practice and in October 2009, an update was published recommending CRP alone as the initial test.²

The use of ESR in the initial diagnosis of temporal arteritis is largely based on its inclusion in the 1990 American College of Rheumatology criteria for classification of temporal arteritis.³ However, this reference is now over 20 years old and the role of ESR as a routine test of the inflammatory response has since been questioned.

ESR and CRP results will sometimes appear discordant when investigating temporal arteritis. In most cases this will be a normal ESR with an elevated CRP, but an elevated ESR and a normal CRP, while unusual, is also consistent with temporal arteritis. In a study which examined the sensitivity of CRP and ESR, it was determined that elevated ESR had a sensitivity of 76% to 86% for temporal arteritis, while an elevated CRP had a sensitivity of 97.5%. When using the criteria of an elevated ESR or CRP, or both, the sensitivity was 99.2%.⁴

Applying this to a clinical context, it is considered that the 1.7% increase in sensitivity gained by using both ESR and CRP compared to the use of CRP alone is not clinically relevant. Any patient with a strong clinical history should have a temporal artery biopsy or empirical treatment irrespective of the results of laboratory tests.