High-res peripheral quantitative CT aids RA tracking and early T2T strategies

In patients with rheumatoid arthritis (RA) receiving treatment, small bone erosions detected in high-resolution peripheral quantitative CT (HR-pQCT) remain stable over 8-year follow-up and are most likely not pathological, while large erosions show meaningful regression under early treat-to-target (T2T) approaches and are most likely to be RA-specific, researchers from the Chinese University of Hong Kong (CUHK) have reported.

“Our findings demonstrate that high-resolution 3D imaging enables precise measurement of the size and distribution of bone erosions, and that not all bone or joint abnormalities are indicative of RA. This approach helps avoid misdiagnosis arising from overinterpretation. It also allows early and accurate diagnosis of true RA cases to enable early treatment,” said coauthor Dr Ho So of the Division of Rheumatology, CUHK.

In the 8-year longitudinal study, 247 patients with RA (median age, 54.8 years; female, 81 percent) and 78 age- and sex-matched healthy controls (median age, 53.3 years; female, 71 percent) underwent HR-pQCT of the second metacarpal head at baseline and 8-year follow-up to quantify volumetric changes of bone erosions. [Ann Rheum Dis 2026;85:1229-1239]

Patients with RA were identified from two cohorts recruited in 2010–2018: an established RA cohort (n=149) treated with usual care and recruited from general rheumatology clinics, and an early RA cohort (n=98) (ie, symptom onset <2 years) managed under a strict T2T algorithm in the first year after diagnosis, which was recruited from a research clinic.

Prioritize tracking of large erosions

At baseline, small erosions (<1 mm³) were similarly prevalent between RA patients and controls (29 vs 26 percent; p=1.000), with minimal volumetric difference between the two groups. Intermediate erosions (1–5 mm³), although more common in RA patients (32 vs 13 percent; p=0.003), showed no significant between-group volumetric difference (p=0.091). Large erosions (>5 mm³) were significantly more prevalent (17 vs 3 percent; p=0.002) and of larger volume (median, 11.6 vs 6.6 mm³; p=0.046) in RA patients.

Over a median follow-up of 8.4 years, substantial improvement in RA disease activity was observed, along with increased use of disease-modifying antirheumatic drugs.

“Despite this, 64 percent of small erosions remained stable at 8-year follow-up. This suggests that small erosions may reflect physiological or biomechanical variants rather than an inflammatory process,” reported co-first author Dr Issac Cheng of the Department of Medicine and Therapeutics, CUHK.

“In contrast, 53 percent of large erosions showed regression at 8 years,” Cheng continued. “Multivariate logistic regression showed that T2T management [in the early RA cohort] was associated with a nearly 7-fold higher odds of regression of large erosions vs usual care [in the established RA cohort] [odds ratio, 6.93; 95 percent confidence interval, 1.57–30.56; p=0.011].”

“Based on these findings, we recommend a ‘sentinel erosion’ strategy that prioritizes tracking large erosions as the primary marker of therapeutic efficacy, while interpreting small erosions with caution to avoid overtreatment,” the researchers noted.