Prospect for an additional laboratory criterion for rheumatoid arthritis

Area of Science:

• Rheumatology
• Immunology
• Clinical Diagnostics

Background:

• Rheumatoid arthritis (RA) diagnosis relies on clinical and laboratory criteria.
• Rheumatoid factor (RF) is a common laboratory marker, but its sensitivity and specificity can vary.
• Novel autoantibodies like antikeratin antibody (AKA) and antiperinuclear factor (APF) are explored for improved RA detection.

Purpose of the Study:

• To assess the diagnostic benefit of incorporating antikeratin antibody (AKA) and/or antiperinuclear factor (APF) positivity as a laboratory criterion for rheumatoid arthritis (RA).
• To compare the performance characteristics (sensitivity, specificity) of AKA and APF against rheumatoid factor (RF) and other established tests.

Main Methods:

• A cohort of 308 hospital patients with recent-onset inflammatory joint diseases was followed for 3 years.
• The study evaluated the sensitivity and specificity of AKA, APF, RF (latex test), and Waaler-Rose test for RA diagnosis.
• Patients were assessed for the presence of joint erosions.

Main Results:

• The latex test showed high sensitivity (.72) but lower specificity (.86), while AKA was highly specific (.96) but less sensitive (.33).
• APF and Waaler-Rose tests demonstrated intermediate performance.
• Patients positive for AKA and/or APF exhibited significantly more joint erosions, indicating a correlation with disease severity.

Conclusions:

• Despite promising performance, the combined use of AKA and APF provided only a moderate increase in RA classification impact compared to using RF alone, due to interrelationships between the markers.
• AKA and APF are not yet suitable for routine general laboratory use due to current limitations and a less extensive data base compared to RF.