[18F] FDG PET/CT discriminates whether rheumatoid arthritis patients are in ultrasound remission or not

Objectives [18F] FDG PET/CT is used for cancer evaluation but can also quantify joint inflammation in rheumatoid arthritis (RA). We evaluated its ability to identify patients in remission as defined by US. Methods Sixty RA patients underwent clinical, PET/CT and US evaluation (hands and wrists). For PET/CT, maximum standardized uptake value (SUVmax) was determined. At the patient level, highest SUVmax, number of PET-positive joints and cumulative SUVmax were recorded. US evaluation included gray-scale (GS) and Power Doppler (PD). Results At the joint level, SUVmax was significantly lower when the joint was under US remission (p < 0.0001). ROC-curves identified a threshold of 0.86 to define joint remission with a high positive predictive value of 95.2%. At the patient level, highest SUVmax and cumulative SUV were significantly lower in patients in US remission (respectively p = 0.0023 and p = 0.045). Highest SUVmax threshold of 2.36 demonstrated a high negative predictive value of 92.9% for determining US remission. For the cumulative SUVmax threshold, the negative and positive predictive values for determining US remission were both 73%. In contrast, these PET/CT parameters did not discriminate if a patient is under clinical remission or not. Conclusions PET/CT can identify RA patients in remission as defined by US. We show that highest SUVmax and cumulative SUV are the two discriminative PET/CT parameters able to determine whether a patient is in US remission. This provides an additional advantage of PET/CT as an objective tool to evaluate RA.