Abstract
Introduction
Fluorodeoxuglucose(FDG) Positron Emission Tomography(PET) scan is used in the diagnosis of prosthetic joint infection, when the inflammatory markers and aspiration of the joint do not establish a definitive diagnosis. The aim of our study was to analyse the utility of FDG PET scan in decision making in these patients.
Methods
We performed a prospective study of patients who underwent a FDG PET scan for suspected prosthetic hip infection, between September 2013 and July 2017. We analysed the results of aspiration, culture and sensitivity, histology of intra-operative samples and inflammatory markers. Our gold standard for diagnosis of infection was 3 or more positive cultures of the same organism. Diagnostic utility statistics for FDG PET were performed.
Results
55 revisions total hip replacements were included. The mean age of the patients was 67.5±4.85 years. The mean ESR, CRP and WCC were 19.83 mm/hr, 22.21 mg/l and 9.05×109/l respectively. The sensitivity and specificity for FDG PET were 93.75% and 35.89% respectively. The positive predictive value(PPV) was 37.5% and negative predictive value(NPV) was 93.33%. The accuracy of detecting an infection was 52.7%. The false positive rate was 62.5%
Discussion
FDG PET has a large number of false positive results and low specificity. If the inflammatory markers and aspiration do not establish infection, addition of FDG PET has limited accuracy in confirming the diagnosis of prosthetic joint infection.
Conclusion
FDG PET may be useful for ruling out infection, but a positive result may not indicate the presence of infection.
