Assessment of joint inflammation at the wrist of patients with rheumatoid arthritis: thermography findings closely mirror those from ultrasonography.

Objectives: To determine if thermography (in comparison with ultrasonography) may be helpful in detecting joint inflammation at the RA wrist categorised according to its clinical manifestations.

Methods: Four wrist groups were derived from the right wrist of RA subjects as follows: (1) swollen; tender (S1T1); (2) swollen; non-tender (S1T0); (3) non-swollen; tender (S0T1); (4) non-swollen; non-tender (S0T0). Thermographic parameters included the maximum (Tmax), average (Tavg) and minimum (Tmin) temperatures. Ultrasound parameters included the Total PD (TPD) and Total GS (TGS) scores. One-way ANOVA and Kruskal-Wallis test (for normally and non-normally distributed imaging parameters, respectively) and subsequent post-hoc tests were carried out for the comparative analysis of the wrist groups.

Results: A total of 70 wrist joints of 70 RA subjects were included in this cross-sectional study. For all imaging parameters (Tmax, Tavg, Tmin, TPD and TGS), statistically significant differences (all p<0.05) were detected (a) between the 4 wrist groups using either the one-way ANOVA or Kruskal-Wallis test and (b) for subsequent pairwise comparison of wrist group 1 (S1T1) vs. group 4 (S0T0) and group 2 (S1T0) vs. group 4 (S0T0). No significant differences (all p>0.05) were found for pairwise comparison of wrist group 3 (S0T1) vs. group 4 (S0T0) for all imaging parameters.

Conclusions: Thermography at the wrist appears promising in RA with its findings closely mirroring those from ultrasonography. Swollen joints (regardless of tenderness status) have higher joint surface temperatures and greater ultrasound-detected joint inflammation, findings which were not observed for tender only (non-swollen) joints.