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I strongly agree with the sentiments of the letter posted by Achim
Nestel(1) in response to the article by Hassan et al(2) regarding the
rarity of C-reactive protein (CRP)-negative giant cell arteritis and the
vital importance of simple blood tests to assist in diagnosis.
However, whilst CRP-negative giant cell arteritis is rare it is not
confined to case reports. A study of 119 cases of biopsy-proven giant cell
arteritis published in 2006(3) revealed that the sensitivity of
erythrocyte sedimentation rate (ESR) was up to 86% and the sensitivity of
CRP was 97.5%. Combining ESR and CRP gave a sensitivity of 99% for
detecting giant cell arteritis.
There were 2 cases out of 119 of CRP-negative disease (although ESR
was elevated in both). This study(3) identified 1 case with normal ESR and
CRP - 'a double negative' which is 0.8% of cases (not 4% as stated by
Hassan et al(2)).
1. Achim R Nestel. BMJ 2011;342:doi:10.1136/bmj.d3685 (Published 20
2. Nada Hassan, Bhaskar Dasgupta, Kevin Barraclough. BMJ
2011;342:doi:10.1136/bmj.d3019 (Published 23 May 2011)
3. Parikh et al. Prevalence of a normal C-reactive protein with an
elevated erythrocyte sedimentation rate in biopsy-proven giant cell
arteritis. Ophthalmology 2006;113:1842-5.