EP31 Musculoskeletal ultrasound of rheumatoid arthritis pregnancy: a single centre experience
Authors: Raine Charles , Manson Jessica , Ciurtin Coziana , Giles Ian 
Published: April 2020

Abstract

Background
The utility of musculoskeletal ultrasound (MSK-US) in the measurement of disease activity of rheumatoid arthritis (RA) is well established. However, it has not been formally studied in pregnancy, with the literature limited to a single case report. Standard disease activity assessment in RA pregnancy comprises measurement of the DAS28(3) CRP score, which removes the visual analogue score (VAS) and replaces ESR with CRP, as both of these components may be confounded by pregnancy. Use of this modified score remains problematic as the tender joint count may be affected by non-specific musculoskeletal pain in pregnancy, and the swollen joint count may be obscured by peripheral oedema, especially late in pregnancy. No study of RA in pregnancy has used MSK-US to measure disease activity. Our objective was to conduct a pilot study of MSK-US in RA pregnancy, and compare findings with clinical assessment using the DAS28(3)CRP score.

Methods
We offered MSK-US to pregnant RA patients attending the UCLH obstetric rheumatology clinic from September 2018 to September 2019. Patients were assessed longitudinally through pregnancy/post-partum where possible. Examination was undertaken using a Logiq S8 US machine. The standard protocol comprised 22-joint assessment of hands (dorsal longitudinal and transverse views of wrists, metacarpophalangeal and proximal interphalangeal joints). In the feet, bilateral MTP joints were scanned with longitudinal views. Quantification of Power Doppler (PD) signal and grey scale (GS) synovitis was made as per the Outcome Measures in Rheumatoid Arthritis Clinical Trials (OMERACT) US definitions. PD and GS scores were calculated as mean scores of all joints scanned.

Results
To date, 17 pregnant RA patients have undergone a total of 35 MSK-US studies. Disease activity assessments showed 10/17 patients with persistent low activity through pregnancy, 5/17 with moderate or good response, 1/17 with no response and 1/17 with a moderate flare. Overall, PD scores correlated well with DAS28(3) CRP assessment (R2 = 0.68). All patients at moderate or high disease activity by DAS28(3) CRP had ≥1 joint with detectable PD signal, but 2/21 patients clinically in ‘remission’ and 3/7 patients in ‘low disease activity’ had detectable PD. One patient with only 2 tender and 1 swollen joints (and normal CRP; DAS28 3.17) had very extensive PD signal and contributed to the decision to recommence anti-TNF treatment in the 3rd trimester. It was noted that increased vascularity in pregnancy can complicate the assessment of synovial PD signal. MSK-US was particularly helpful in distinguishing true joint synovitis from subcutaneous oedema in the feet.

Conclusion
This is the first series of MSK-US in pregnant RA patients. The detection of active joint synovitis (by PD signal) in clinical remission/low disease activity states suggests a potential role for MSK-US in confirming apparent low disease activity in pregnancy, and thus guiding stratification of treatment.

Disclosures
C. Raine None. J. Manson None. C. Ciurtin None. I. Giles None.