In addition to being sensitive enough to assess anatomical changes, disease activity, and therapeutic efficacy, ultrasound is safe, noninvasive, patient friendly, free of ionizing radiation, and less expensive than other imaging methods. It also allows multiple target assessment in real time without the need for external referral. Compared with conventional radiography, magnetic resonance imaging (MRI), or computed tomography (CT), power Doppler ultrasound can simultaneously reflect a change in inflammatory activity by accurately measuring blood flow changes and assess the progression of anatomical damage.
Question: What are the strengths and weaknesses of the preliminary power Doppler ultrasound composite score?
Dr. Gutierrez: Our preliminary composite score, called Five Targets Power Doppler for Psoriatic Disease (5TPD), includes the assessment of changes in joints, tendons with synovial sheath, entheses, skin, and nails. It represents a feasible, reliable, and comprehensive approach for multitarget monitoring of PsA.
The score is based on the simple arithmetic sum of the scores regarding the five clinical targets. Power Doppler for each target is graded from 0 to 3 on the basis of the semiquantitative scoring systems previously suggested. The maximum total score of 5TPDis 15. In our study, the instrument was found to possess both face and content validity, and it exhibited good responsiveness. By documenting these key measurement properties, we have shown that the 5TPD is a useful instrument for the assessment of disease activity and responsiveness in PsA patients and is, therefore, potentially applicable in standard clinical care, observational studies, and clinical trials.
The 5PTD is feasible and easy to perform in the hands of expert sonographers. The baseline assessment takes an average of 10.5 minutes. The follow-up complete examination, including calculating the score, averages no more than 7 minutes, which makes it quite practical in busy clinical settings.
The main limitation of the score currently is that it was tested in a small cohort of patients, which does not allow for an accurate evaluation in terms of the sensitivity and specificity needed to support our results more strongly. Also, we need to consider the ceiling effect. For example, high composite ultrasound scores denote the involvement of multiple target areas of psoriatic disease, and they can be shared by patients with relevant differences in terms of the extent of the inflammatory involvement at each specific target area. In other words, a severe inflammation of a single joint showing a power Doppler grade of 3 gives the maximum contribution to the final score; an equally severe inflammation in terms of power Doppler appearance, but polyarticular involvement, cannot provide more than 3 and thus would be easily underestimated. We are currently developing steps aimed at defining a linear cutoff value point for any single domain of 5TPD to resolve this aspect.
It is important to remember that this composite score was designed to monitor PsA disease activity in daily practice after a complete clinical examination, and not to replace other well-established and accepted ultrasound assessments.
Question: What is next for the 5TPD?
Dr. Gutierrez: Investigations are ongoing to assess the advantages and limitations of the formula in wider cohorts of patients. The composite score needs further development and concurrent and discriminate validation through randomized controlled trials and longitudinal observational studies. The tool is currently being evaluated prospectively as part of a larger multicenter study, as well as in a study comparing it with the CPDAI for the assessment of disease activity and responsiveness.
–Interview by Diana Mahoney
Dr. Gutierrez is scientific director of the Pan-American League of Associations for Rheumatology (PANLAR) Ultrasound Group. He reported having no financial conflicts of interest.