The predictive value of SS-16 in clinically diagnosed Parkinson’s disease patients: comparison with (99m)Tc-TRODAT-1 SPECT scans

BACKGROUND: Dopamine transporter based imaging has high diagnostic performance in distinguishing patients with Parkinson’s disease (PD) from patients with non-Parkinsonian syndromes. Our previous study indicated that the “Sniffin’ Sticks” odor identification test (SS-16) acts as a valid instrument for olfactory assessment in Chinese PD patients. The aim of the study was to compare the efficacy of the two methods in diagnosing PD. METHODS: Fifty-two PD patients were involved in this study and underwent single photon emission computed tomography (SPECT) imaging using the labeled dopamine transporter radiotracer (99m)Tc-TRODAT-1 to assess nigrostriatal dopaminergic function. Olfactory function was assessed with the “Sniffin’ Sticks” odor identification test (SS-16) in all patients who received DAT-SPECT scanning. Statistical analysis (SPSS version 21) was carried out to determine the diagnostic accuracy of SS-16 as well as its correlation with (99m)Tc-TRODAT-1 SPECT, its positive predictive value (PPV), and negative predictive value (NPV). RESULTS: We identified a negative correlation between SS-16 and DAT SPECT (Kappa = 0.269, p = 0.004). By using the (99m)Tc-TRODAT-1 uptake results as the gold standard, the sensitivity and specificity of SS-16 was 56.8 and 37.5 %, respectively. Furthermore, the negative and positive predictive values were calculated as 13.6 and 83.3 %, respectively. CONCLUSIONS: SS-16 would not be used as a diagnostic tool for early stage PD patients. Negative results of SS-16 would not exclude the diagnosis of PD. Further tests are needed for validation.