Perspective:

PET scans are often used for diagnosis and therapeutic monitoring of patients with known or suspected sarcoidosis. PET scans are usually performed with a perfusion agent (such as rubidium-82 or N-13 ammonia) to identify areas of hypoperfusion related to scar/fibrosis or, possibly, edema. A second scan is generally performed with FDG in order to identify areas of inflammation. Importantly, careful metabolic preparation with a very low-carbohydrate diet is essential to avoid false positive FDG PET (20% or more of scans may be false positive or nondiagnostic even with relatively careful preparation). These scans are complex and require fastidious preparation by patients and careful interpretation by physicians. This study provides large-scale data supporting the clinical value of these efforts.

Importantly, the study does not evaluate whether these scans are more useful than other approaches or whether PET-guided management of immunosuppression improves clinical outcomes in this population. Future studies are required to evaluate those questions more rigorously.