Abstract: Objective: To detect the interleukin-6 (IL-6) levels and expressions of applipoprotein E (ApoE) in the Alzheimer's disease (AD) patients with different body-mass indexes (BMI), and to explore the diagnotic value of ¹¹Pittsburgh comound-B (¹¹C-PIB) combined with ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) PET/CT imaging in AD. Methods: A total of 58 AD patients were divided into four groups according to their BMI:low BMI group(BMI <18.5 kg·m^-2,n=18),normal BMI group(18.5 kg·m^-2 ≤ BMI <24.9 kg·m^-2,n=13),high BMI group(24.9 kg·m^-2 ≤ BMI <29.9 kg·m^-2,n=12)and obese group(BMI ≥ 29.9 kg·m^-2,n=15). All the patients underwent PET/CT imaging (¹¹C-PIB and ¹⁸F-FDG). The sensitivity,specificity and accuracy rate, the expression rates of ApoE (ε2, ε3, and ε4) and the levels of serum IL-6 were detected. The relationship between BMI and the expression rates of ApoE and the serum levels of IL-6 were analyzed by Spearman analysis. Results: The sensitivity, specificity, and accuracy rate of the patients in low BMI group diagnosed by ¹¹C-PIB and ¹⁸F-FDG PET/CT were 87.5%,80.0%, and 84.6%, which were higher than those diagnosed by ¹¹C-PIB (55.6%,50.0%, and 53.8%) or ¹⁸F-FDG (42.9%,50.0%, and 46.2%)alone (P<0.05). The serum levels of IL-6 and BMI of the AD patients had a negative correlation(r=-0.407,P=0.002).The expression rate of ApoE ε4 allelic gene(60.3%) of the AD patients was higher than those of ε2(18.9%) and ε3 allelic genes(20.7%), but there was no correlation between the BMI and the expression rates of different ApoE allelic genes of the AD patients(r=-0.028,P=0.833). Conclusion: ¹¹C-PIB and ¹⁸F-FDG PET/CT has a high diagnotic value in the AD patients. ¹¹C-PIB and ¹⁸F-FDG combinated with serum IL-6 level and BMI could diagnose and evaluate AD more exactly.

Key words: Alzheimer's disease, interleukin-6, positron emission tomography, ¹⁸F-fluorodeoxyglucose, ¹¹C pittsburgh compound-B, body mass index, applipoprotein E, computed tomography