Harry Spoelstra
[⁶⁸Ga]FAPI PET/CT: persistent fibroblast activity years after severe COVID, the mounting evidence. [⁶⁸Ga]FAPI PET/CT maps fibroblast activation protein on activated fibroblasts, the cells driving tissue remodelling and fibrosis. Unlike ¹⁸F-FDG (inflammation/glucose), FAPI can stay positive when FDG is silent. Two independent post-ICU/severe-COVID cohorts now show the same signal ~2–2.5 years later: 1. Groningen (van Leer et al., EJNMMI 2025): 18 PASC vs 15 controls, median 30 months. Pulmonary target-to-background ratio(TBR) 0.79 vs 0.40 (P<0.001). Paravertebral muscle uptake also higher. Lung TBR inversely correlated with FEV1/FVC and modestly with % Ground-glass opacities (GGO). Muscle uptake tracked with fatigue measured after a 6-minute walk test(post-6MWT fatigue). https://link.springer.com/article/10.1007/s00259-025-07376-y 2. Recent Turkish pilot study(Hasan et al., 2026): 20 PASC vs 10 controls, ~25 months after high-flow nasal cannula(HFNC)/ventilation. Higher lung FAPI, especially with traction bronchiectasis and SUVmean inversely correlated with DLCO. Muscle uptake again elevated after mechanical ventilation. https://www.sciencedirect.com/science/article/abs/pii/S2253808926000662?via%3Dihub ➡️Same pattern, two centres: lungs and muscles, and we already had other science signals. ➡️This is still small, post-critical, and not histology-proven. ➡️Interesting would now be the next step: Groningen’s LIBERATE trial (NCT06911476): ~60 patients with dyspnoea/fatigue regardless of original severity, ongoing vs resolved symptoms( =awaiting results). 🤔The recent Turkish paper is not an isolated finding. It independently reproduces the Groningen 2025 results (increased lung and muscle FAPI signal years after severe COVID). Together with the 2022 Innsbruck series and the 2024 “FAPI-negative scar” case, there is a coherent signal that activated fibroblasts can persist long after the acute infection in a subset of patients. Whether this is a useful tracker for routine Long COVID lung pathology, or only a research tool in post-critical cases, is still open. The next Groningen trial is the one most likely to answer that. ‼️So, years after moderate to severe COVID19, FAPI PET shows ongoing fibroblast-related remodelling, an objective biological footprint, not “just tired.” It could become a candidate biomarker for activity vs burnt-out scar but is not yet a routine test. Larger non-ICU data will decide clinical use. Until then: take post-COVID19(#LongC0VID) persistent dyspnoea seriously, and do not treat it as purely functional. And probably even more important: #AvoidReinfections!
