Clinical use of computer-aided joint-space analysis (CAJSA) provides a reliable calculation of joint-space distances (JSD) at the metacarpophalangeal (MCP) joint for quantification of joint changes related to rheumatoid arthritis (RA). Calculation of a Z-score helps distinguish disease-related narrowing of JSD from age-related changes.
Pfeil and associates used CAJSA to compare the JSD of the MCP joint in 248 persons with RA and in 256 healthy subjects with digital hand radiographs. Radiographs were scored using Sharp’s joint-space narrowing method. JSD-MCP in patients with RA was compared with the age-matched reference values of healthy subjects using the Z-score. The researchers also sought to distinguish sex-related alterations from RA-related joint-space narrowing.
Women had significantly smaller joint-space widths than men. A relationship between age and joint-space width was found in all study participants. Although persons with RA had narrower joint spaces than controls, both groups had a reduction in joint space as they aged. The CAJSA method and the Z-score both could differentiate normal age-related joint space changes from those caused by RA. Patients with RA had lower Z-scores than those without.
The authors noted that calculating the Z-score based on age and sex data may lead to earlier RA diagnosis and intervention.