Does hyperglycemia affect the diagnostic value of 18F-FDG PET/CT?

Net cellular uptake of (18)F-FDG is adversely affected by elevated plasma glucose levels. The purpose of our study was to investigate the influence of hyperglycemic state at the time of (18)F-FDG injection on the diagnostic accuracy of (18)F-FDG PET/CT.

Pre-scan plasma glucose levels of all patients who were referred for PET/CT with an oncologic indication during the year 2005 were reviewed. All seventy-six patients (50 men, 26 women, mean age ± SD: 65.5 ± 9.7 years) with pre-scan glucose level higher than 140 mg/dL (mean plasma glucose level ± SD: 168.7 ± 30.8, ranging from 140 to 260 mg/dL) were enrolled into our study. The accuracy of PET/CT scans was assessed using concurrent or follow-up CT, MRI and histologic evidences as well as clinical follow-up as the reference standard.

PET/CT was true positive in 37 patients, true-negative in 30 patients, false negative in 6 patients and false positive in 3 patients. Overall sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy of (18)F-FDG PET/CT on a patient basis were 86%, 90.9%, 92.5%, 83.3% and 88.1%, respectively. Diabetes mellitus was recorded in 50 patients. No significant diagnostic accuracy difference between diabetics and non-diabetics was noticed.

Our study suggests that (18)F-FDG accumulation of malignant lesions remains sufficiently high for reliable qualitative clinical diagnosis in chronic and acute hyperglycemic states. However, regarding the discordant and inconclusive results of the available reports and the remarkable concerns with reference to the adverse effects of elevated plasma glucose levels on the diagnostic accuracy of (18)F-FDG PET/CT scans, further direct clues seems to be required and should be provided by future studies.