Aim: The main objective of the IMPAACT study is to describe the histological findings of
PsA Achilles enthesitis, and to a) Characterize and b) Quantify the immune-competent cell
presence in tendon specimens obtained from the mid-portion and entheseal site of the
Achilles tendon from PsA patients with enthesitis using immunohistochemistry and a
stereological technique for the quantification. And secondly, to compare these
observations with a) Those in healthy Achilles tendons, and b) Those in mono-symptomatic,
non-PsA, chronic Achilles tendinopathy. Secondly, to examine whether one or more of the
immune-competent cell types in the PsA tendons are associated with 3-months remission
rate of Achilles tendon pain, or with baseline a) Ultrasonic findings of the Achilles
tendon; b) PsA disease activity; c) Tendon protein analyses; d) Risk factors of
cardiovascular disease; e) Blood biomarkers of systemic inflammation; and f) Fecal
microbiota composition.
Methods: This study (IMPAACT) is a prospective, cohort study including 30 PsA patients
(fulfilling the the Classification Criteria for Psoriatic Arthritis (CASPAR criteria))
with pain at the Achilles tendon insertion. At baseline, all participants will be
examined clinically regarding overall PsA disease activity (Psoriasis Area Severity Index
(PASI skin score), the Research Consortium of Canada (SPARCC) Enthesitis score,
swollen/tender joint count) and asked to fill out a questionnaire consisting of the
validated Scandinavian (Danish) version of the Victorian Institute of Sport Assessment of
Achilles tendons (VISA-A) in addition to a study-composed questionnaire comprising
general questions regarding patient characteristics. An ultrasonic examination of the
Achilles tendons will be performed before ultrasound guided Achilles tendon specimens
will be obtained from the most painful Achilles tendon. Tendon samples will be evaluated
immunohistochemically by quantifying the presence of macrophages (CD68-KP1+),
T-lymphocytes (CD3+), B-lymphocytes (CD20+), natural killer cells (CD56+), neutrophils
(granzyme-B+), mast cells and inflammatory markers using a stereological technique. Also,
a protein analysis of the tendon tissue will be conducted. Venous blood will be analysed
for levels of systemic inflammatory markers, as well as screened for cardiovascular risk
factors including dyslipidaemia, and diabetes. After the baseline examination, all
participants will be treated and monitored in accordance with the Danish national
guideline recommendations for PsA patients. A 3-months follow-up examination will be
performed to determine the remission status of the Achilles tendon pain. Data will be
analysed using the STATA statistical package.
Conclusion: PsA is a painful and debilitating inflammatory disease. The current treatment
remains suboptimal. We hope to provide new insight into the cellular mechanisms
underlying PsA tendon and enthesis pathologies.
