A genetic association study of serum acute-phase C-reactive protein levels in rheumatoid arthritis: Implications for clinical interpretation

Benjamin Rhodes, Marilyn E. Merriman, Andrew Harrison, Michael J. Nissen, Malcolm Smith, Lisa Stamp, Sophia Steer, Tony R. Merriman, Timothy J. Vyse

Research output: Contribution to journalArticle

43 Citations (Scopus)

Abstract

Background: The acute-phase increase in serum C-reactive protein (CRP) is used to diagnose and monitor infectious and inflammatory diseases. Little is known about the influence of genetics on acute-phase CRP, particularly in patients with chronic inflammation. Methods and Findings: We studied two independent sets of patients with chronic inflammation due to rheumatoid arthritis (total 695 patients). A tagSNP approach captured common variation at the CRP locus and the relationship between genotype and serum CRP was explored by linear modelling. Erythrocyte sedimentation rate (ESR) was incorporated as an independent marker of inflammation to adjust for the varying levels of inflammatory disease activity between patients. Common genetic variants at the CRP locus were associated with acute-phase serum CRP (for the most associated haplotype: p = 0.002, p<0.0005, p<0.0005 in patient sets 1, 2, and the combined sets, respectively), translating into an approximately 3.5-fold change in expected serum CRP concentrations between carriers of two common CRP haplotypes. For example, when ESR = 50 mm/h the expected geometric mean CRP (95% confidence interval) concentration was 43.1 mg/l (32.1-50.0) for haplotype 1 and 14.2 mg/l (9.5-23.2) for haplotype 4. Conclusions: Our findings raise questions about the interpretation of acute-phase serum CRP. In particular, failure to take into account the potential for genetic effects may result in the inappropriate reassurance or suboptimal treatment of patients simply because they carry low-CRP-associated genetic variants. CRP is increasingly being incorporated into clinical algorithms to compare disease activity between patients and to predict future clinical events: our findings impact on the use of these algorithms. For example, where access to effective, but expensive, biological therapies in rheumatoid arthritis is rationed on the basis of a DAS28-CRP clinical activity score, then two patients with identical underlying disease severity could be given, or denied, treatment on the basis of CRP genotype alone. The accuracy and utility of these algorithms might be improved by using a genetically adjusted CRP measurement.

Original languageEnglish
Article numbere1000341
JournalPLoS Medicine
Volume7
Issue number9
DOIs
Publication statusPublished - 21 Sep 2010
Externally publishedYes

Bibliographical note

This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Fingerprint Dive into the research topics of 'A genetic association study of serum acute-phase C-reactive protein levels in rheumatoid arthritis: Implications for clinical interpretation'. Together they form a unique fingerprint.

Cite this