The predictive value of C-reactive protein and erythrocyte sedimentation rate for 18F-FDG PET/CT outcome in patients with fever and inflammation of unknown origin.

Objectives: The objective of this study was to determine the predictive value of C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) to a positive fluorine-18 fluorodeoxyglucose ((18)F-FDG) PET/computed tomography (CT) result in patients with inflammation of unknown origin and fever of unknown origin.

Patients And Methods: Individual data of 498 patients were retrieved from three retrospective studies. Receiver operating characteristic derived areas under the curve were used to assess (18)F-FDG PET/CT versus age, CRP, and ESR. The discriminative value of age, CRP, and ESR related to (18)F-FDG PET/CT was examined using the net reclassification improvement (NRI).

Results: A diagnosis was established in 331 patients; (18)F-FDG PET/CT had a diagnostic accuracy of 89%. (18)F-FDG PET/CT had the highest area under the curve (0.89, P<0.001). The addition of (18)F-FDG PET/CT to a diagnosis prediction model including age, CRP, and ESR resulted in an NRI of 42% (P<0.001). In the same model with CRP values below 20 mg/l or ESR values below 20 mm/h, the NRI was 64% (P<0.001) and 29% (P=0.059), respectively. In 30 of 91 patients with CRP less than 10 mg/l, a diagnosis could be established; (18)F-FDG PET/CT was 100% true negative only in patients with CRP levels less than 5 mg/l.

Conclusion: In patients with fever of unknown origin or inflammation of unknown origin, compared with elevated ESR levels, elevated CRP levels more often indicate a true positive (18)F-FDG PET/CT outcome.In addition, (18)F-FDG PET/CT, compared with CRP and ESR, shows the highest discrimination of patients with possible disabling disease.