Fibroblast activation protein inhibitor positron emission tomography imaging in muscles of patients with idiopathic inflammatory myopathy
Authors' conclusion
Increased [18F]FAPI-42 uptake was associated with muscle oedema in IIM. FAPI-derived parameters correlated with IIM disease activity.
Study context
- Population
- Patients with idiopathic inflammatory myopathy (IIM) imaged January 2023 to July 2023; controls with malignancies
- Participants
- 26 vs 28
- Exposure
- IIM vs controls with malignancies
- IIMn = 26
- Controlsn = 28reference
- Outcome
- Global FAPI-avid muscle ratio
Methodological details[18F]FAPI-42 PET/CT, whole-body MRI in IIM
- [18F]FAPI-42 PET/CT
- Whole-body MRI in IIM
Main finding
As reported in the abstract
IIM
0.68
IQR 0.45–0.79
Controls
0.06
IQR 0–0.11
P < 0.001
Observational data: associations, not effects.
Further findings
| Outcome | IIM | Controls | P value |
|---|---|---|---|
| Global muscle TBR | 2.26 (IQR 1.71–2.75) | 1.23 (IQR 1.02–1.52) | P < 0.001 |
| Muscle TBR, muscles with vs without oedema (IIM) | P < 0.001 |
- Muscle target-to-background ratio (TBR), muscles with vs without oedema (IIM): Muscles with oedema median 2.44 (IQR 1.46–3.27)
- Muscle TBR, muscles with vs without oedema (IIM): Muscles without oedema median 1.31 (IQR 0.95–1.99)
Correlations of global fibroblast activation protein inhibitor (FAPI)-avid muscle ratio (IIM)
- Global oedema score, r
- 0.833
- Muscle strength, r
- −0.649
- Serum creatine kinase, r
- 0.456
- Disease activity index, r
- 0.495-0.621
Original publication
Fibroblast activation protein inhibitor positron emission tomography imaging in muscles of patients with idiopathic inflammatory myopathy. Rheumatology (Oxford). Published 16 September 2024. doi:10.
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