The diagnostic value of minor salivary gland biopsy in clinically diagnosed patients with Parkinson's disease: comparison with DAT PET scans

To investigate the predictive value of minor salivary gland biopsy in clinically diagnosed early stage Parkinson's disease (PD) patients, and to provide more evidence of minor salivary gland biopsy as a pathological diagnostic biomarker of PD. Thirteen patients with early stage PD and 13 age-matched controls were recruited. Hoehn and Yahr stage and Unified Parkinson's disease Rating Scale Part III were employed to evaluate their severity of the disease. All the subjects underwent minor salivary gland biopsy and C-11-methyl-N-2 beta-carbomethoxy-3 beta-(4-fluorophenyl) tropane (C-11-CFT) DAT-PET scan. Immunohistochemical staining for Lewy-type alpha-synucleinopathy using antibody against alpha-synuclein (alpha-Syn) was performed in the tissues obtained from minor salivary gland. Abnormal accumulation of alpha-Syn was found around the gland cells in 9 of the 13 patients with PD, but in none of the control subjects. The alpha-Syn immunoreactive structures were located in the periacinar space. Twelve clinically diagnosed PD patients showed asymmetrical and relatively severe reduction of C-11-CFT uptake in the posterior putamen compared with the control. The sensitivity, specificity, positive predictive value and negative predictive value of minor salivary gland biopsy were 75, 100, 100 and 25%, respectively, when compared with the DAT-PET imaging. Our results suggest that minor salivary gland biopsy does not hold high diagnostic accuracy as DAT-PET, but still has the potential to be a useful pathologic biomarker for PD, which is worth more investigations.