Selective hyposmia in Parkinson's disease?

Dear Sirs,In 1993 Hawkes and Shephard [1] presented data onrelative selectivity of the smell defect in Parkinson’sdisease (PD). By using the University of Pennsylvaniasmell identification test (UPSIT) they demonstrated themost significant result for pizza and wintergreen in dis-criminating PD patients from healthy controls, with a90 % sensitivity and 86 % specifity. They discussed thepossibility of a congenital or acquired selective hyposmiain PD and recommended selective olfactory testing for PDdiagnosis. Currently, the practical benefits of selectivetesting results are disputed. Whereas Hawkes reported ontwo UPSIT odours, Double et al. [2] found that fivespecific odors (gasoline, banana, pineapple, smoke, andcinnamon) of the short version of the UPSIT, the B-SIT,discriminate PD patients most effectively, while pizza,mint, and licorice were optimal in the study by Silveira-Moriyama et al. [3]. In a German study [4], however,cinnamon was found to be ineffective for PDdiscrimination. In the work by Doty et al. [5], no evi-dence of a pattern of PD-related smell loss to specificUPSIT items was found. These data suggest that selectivetesting results mainly rely on the olfactory test anddescriptor items used as well as the study population andcultural differences, but no systematic studies are avail-able comparing odour identification in PD with hyposmiadue to other causes.We investigated 35 PD patients (mean age 64 years,range 44–82 years, 22/13 male/female) in comparison to35 patients with post-viral (n = 16), posttraumatic(n = 5), sinonasal (n = 7), or idiopathic (n = 7) olfactoryloss (mean age 59 years, range 24–81 years, 18/17 male/female) to determine whether odour identification in PDdiffers from that in non-Parkinsonian hyposmia. With asample size of 35 in each group, a Chi square test with a0.05, two-sided significance level had an 80 % power todetect a sufficient difference between the two patientgroups. For overall olfactory assessment, we used thevalidated 16-item ‘‘Sniffin