Diagnostic performance and predictive value of serum markers for the diagnosis of rheumatoid arthritis
Received: 16 January 2004
Published: 24 February 2004
Keywords
Background
Rheumatoid factor (RF) is the classical serum marker for rheumatoid arthritis (RA). Anti-citrullinated peptide antibodies (ACPA) have a higher sensitivity and specificity (spec) for RA.
Objective
Our aim was to evaluate the diagnostic and predictive value for RA of RF and antibodies to pepA and pepB (two synthetic substrates for ACPA detection) in a setting relevant to routine clinical practice.
Methods
In this prospective multicentre study, samples were collected at academic and nonacademic centres from 1003 consecutive patients presenting for diagnostic work-up when the clinician included RA in the differential diagnosis. RF was detected by latex fixation. A research INNO-LIA™ RA (Innogenetics, Belgium) was used to detect anti-pepA and anti-pepB antibodies. Diagnoses were made by the clinician using ACR criteria after 1 year follow-up. ROC curve analysis was used to evaluate the diagnostic performance of the tests.
Results
ROC curves.
Diagnostic performance of serum markers using different cut offs
Antibody | Cutoff | Sensitivity (%) | Specificity (%) | PPV (%) |
|---|---|---|---|---|
PepA | Low | 63.6 | 90.6 | 60.7 |
PepB | 64.3 | 90.0 | 59.0 | |
RF | 69.2 | 90.1 | 61.5 | |
PepA | Intermediate | 62.9 | 95.1 | 74.4 |
PepB | 61.5 | 95.1 | 73.3 | |
RF | 55.2 | 94.6 | 69.9 | |
PepA | High | 58.7 | 98.1 | 87.5 |
PepB | 48.3 | 98.1 | 85.2 | |
RF | 42.0 | 97.8 | 81.1 | |
PepA | Very high | 41.3 | 99.0 | 90.8 |
PepB | 37.1 | 99.0 | 89.8 | |
RF | 21.0 | 99.0 | 83.3 |
Conclusion
When high specificity is required, anti-pepA and anti-pepB antibodies have a markedly higher sensitivity than RF. The highest PPV are found when ACPA are very high.
