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

TL;DR

18F-FDG PET/CT can detect if rheumatoid arthritis patients are in ultrasound-defined remission, offering an objective tool for evaluation.

Contribution

The study identifies PET/CT parameters that can distinguish RA patients in ultrasound remission from those who are not.

Findings

SUVmax was significantly lower in joints in ultrasound remission (P < 0.0001).

A threshold of 2.36 for highest SUVmax had a 92.9% negative predictive value for US remission.

Cumulative SUVmax threshold showed 73% predictive value for determining US remission.

Abstract

18F-FDG PET/CT is used for cancer evaluation but can also quantify joint inflammation in RA. We evaluated its ability to identify patients in remission as defined by US.

Sixty RA patients underwent clinical, PET/CT and US evaluations (hands and wrists). For PET/CT, the maximum standardized uptake value (SUVmax) was determined. At the patient level, the highest SUVmax, number of PET-positive joints and cumulative SUVmax were recorded. US evaluation included gray-scale and power Doppler.

At the joint level, SUVmax was significantly lower when the joint was in US remission (P < 0.0001). Receiver operating characteristics curves identified a threshold of 0.86 to define joint remission with a high positive predictive value of 95.2%. At the patient level, the highest SUVmax and cumulative SUV were significantly lower in patients in US remission (respectively P = 0.0023 and P = 0.045). The 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 in clinical remission or not.

PET/CT can identify RA patients in remission as defined by US. We show that the 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.