To the Editor:

We thank our colleagues, Drs. Scheel and Backhaus, for their interest in and comments on our recent study. We are pleased to be given the opportunity to elaborate on the description of our methodology.

Except for our intention to assess finger as well as toe joints, the only criterion for our preselection of joints for examination was their accessibility for ultrasound. In this respect, the PIP joints are most accessible and can be assessed in 4 aspects (dorsal, palmar, medial, and lateral). The accessibility of the MCP joints varies, with the second and fifth MCP joints being accessible in 3 aspects (dorsal and palmar and, respectively, medial and lateral), while the third and fourth MCP joints are accessible in only 2 aspects (dorsal and palmar). This variability of accessibility is also seen in the MTP joints, where the first MTP joint is accessible in 2 aspects (medial and dorsal, due to the presence of the sesamoid bones on the plantar side of the joint), the fifth MTP joint is accessible in 3 aspects (dorsal, plantar, and lateral), while the second, third, and fourth MTP joints are accessible in 2 aspects (dorsal and plantar). We considered the 5 preselected joints to be representative of the finger and toe joints involved in rheumatoid arthritis, with respect to location, size, and accessibility. Thus, the distribution of joint changes in rheumatoid arthritis had no influence on our selection. However, we think that the differences described by Drs. Scheel and Backhaus suggest that our choice of joints for examination included different frequencies of involvement.

The examinations in our study were performed according to a protocol on which we reached consensus before its beginning. The preselected joints were examined from all accessible aspects (see above), in both the longitudinal and transverse aspects, as shown in the figures. The longitudinal aspects were used for scoring synovitis, joint effusion, and power Doppler flow signal, while both longitudinal and transverse aspects were used for scoring the destructive changes.

Our experience is that synovitis and joint effusion are most often visualized on the dorsal side of the MCP and MTP joints, but in the PIP joints the findings predominate on the palmar side. Likewise, in our experience, it is most often joint effusion in the PIP joints that can be visualized along the diaphysis. On the basis of a cross-sectional study, we cannot conclude which of the findings is primary. We can only state that in our patient population, the combination of synovitis and joint effusion often occurred in the MTP and PIP joints and seldom occurred in the MCP joints. In order to elucidate patterns of localization of these parameters in future longitudinal studies, we prefer to score them separately.

We find our results encouraging for the further use of ultrasound imaging in rheumatoid arthritis and agree with Drs. Scheel and Backhaus that a final evaluation of a scoring system should occur in longitudinal studies, with a higher number of participants, including both patients and healthy controls.

Marcin Szkudlarek MD, PhD*, Michel Court-Payen MD, PhD*, Søren Jacobsen MD, DMSc*, Mette Klarlund MD, PhD*, Henrik S. Thomsen MD, DMSc†, Mikkel Østergaard MD, PhD, DMSc* †, * University of Copenhagen Hvidovre Hospital, Hvidovre, Denmark, † University of Copenhagen Herlev Hospital Herlev, Denmark.