Die Wertigkeit des 18F-FDG-PET/CT zur Entzündungs-/Tumorsuche bei Patienten mit unklarer neurologischer Symptomatik.

Background There are a variety of neurological symptoms that lead to a diagnosis through comprehensive investigations using anamnesis, neurological status, MRI, biochemical and molecular genetic laboratory diagnostics, and neurophysiological diagnostics. Nevertheless, in some patients no diagnosis is found. 18F-FDG-PET/CT can be used as another diagnostic measure. Aim The aim of this retrospective study was to investigate the diagnostic performance of 18F-FDG-PET/CT in a collective of previously undiagnosed patients. Methods For this purpose, the findings of already performed 18F-FDG-PET/CT examinations from the database of the Department of Nuclear Medicine of the University Hospital Giessen and Marburg were compared with further examinations and the final diagnosis in 93 patients. The 18F-FDG-PET/CT is an imaging technique that reflects a fused data set of metabolic (PET) as well as morphological (CT) processes in the body. Results After evaluation of the data, it could be concluded that 18F-FDG-PET/CT was shown to be helpful in the correct identification of healthy patients. The specificity was 85%, and the positive predictive value was 75%. Thus, 18F-FDG-PET/CT may be a suitable tool for inclusion of disease when the specific question is addressed. Furthermore, early indication of 18F-FDG-PET/CT may be useful to avoid further invasive diagnostics and therapies. An increase in specificity can be achieved by prior delineations, such as time of performance of 18F-FDG-PET/CT, symptomatic grouping of the disease, and period of disease. For diagnostic detection of disease in patients with unclear neurologic symptoms, 18F-FDG-PET/CT has only a weak sensitivity. However, these patients undergo a large number of examinations until the indication for 18F-FDG-PET/CT is made. In relation to this procedure, a sensitivity of 47% is to be rated as questionable. For a better assessment, further studies that include the 18F-FDG-PET/CT earlier in the diagnostic process are necessary. In this study, we also considered antibodies in relation to 18F-FDG-PET/CT. We determined a sensitivity and specificity of 73% and 37%. The positive predictive value in patients with positive antibody titers was 36%. In the heterogeneous patient population, the benefit of determining antibodies in combination with 18F-FDG-PET/CT is questionable. It should be noted that no quantitative antibody measurements were included in the study. Therefore, a study including antibody titers would be useful to determine possible cut-off values and increase the diagnostic value. Determination of antibodies alone without reference to 18F-FDG-PET/CT also has only a poor specificity and sensitivity. Thus, it is not suitable for inclusion as well as exclusion of diseases. The low specificity and sensitivity may also be due to the heterogeneous patient population. Conclusion In conclusion, the success rate of an earlier indication in the described patients remains questionable. It must be clarified whether it leads to an increase in sensitivity if the 18F-FDG-PET/CT is used as a method before most other examinations. Thus, the results obtained in this study indicate that further investigations on this issue may be worthwhile. The results of the further studies should be subsequently analyzed in terms of radiation exposure and costs. The 18F-FDG-PET/CT should be critically evaluated at this point of the diagnostic sequence due to radiation exposure and costs.