Validity aspects of erythrocyte sedimentation rate and C-reactive protein in ankylosing spondylitis: A literature review

The preliminary core set for endpoints in disease controlling antirheumatic therapy includes acute phase reactants, The objective of this clinically o riented literature review was to examine and compare the validity of erythr ocyte sedimentation rate (ESR) and C-reactive protein (CRP) in ankylosing s pondylitis (AS) clinical trials. A MEDLINE search was performed covering th e years 1967 through April 1998. AS studies were identified and selected if they included ESR andlor CRP and either presented data about their relatio n with disease activity or were designed as longitudinal clinical trials. A dditional studies were identified by scrutinizing references cited in the r etrieved studies. The selected studies were examined for truth (association with disease activity), discriminative power (sensitivity to change and di scrimination between active and inactive treatment in longitudinal clinical trials), and feasibility (e.g., applicability and costs) of ESR and CRP in AS. We identified 12 articles on the association of ESR andlor CRP with di sease activity and 13 longitudinal clinical trials reporting ESR and/or CRP data Although the applied definitions or disease activity proved very inho mogenous, there was some evidence that both acute phase reactants are corre lated with disease activity, In terms of discriminative capacity the availa ble data are inconclusive. Relevant feasibility aspects are general availab ility, technically simple measurement, and an advantage in the cost of ESR and central laboratory facilities for CRP. Acute phase reactants do not com prehensively represent the disease process in AS. Their worth in AS clinica l trials is limited. Based on the currently existing data neither measure i s clearly superior in terms of validity. When selecting an acute phase reac tant, feasibility aspects may be most relevant in choice of measure.