Characteristics of Smell Identification Test in Patients With Parkinson Disease

Parkinson disease (PD) is frequently associated with olfactory disorder at early stage, which is caused by deposition of Lewy bodies emerging from the olfactory bulb to higher olfactory centers. Early detection of olfactory disorder in the patients with PD may lead to the early diagnosis and treatment for this refractory disease.

Visual analog scale (VAS), Jet Stream Olfactometry, and Japanese smell identification test, Open Essence (OE), were carried out on 39 patients with PD. Thirty-one patients with postviral olfactory disorder (PVOD), which was caused by the olfactory mucosal dysfunction, were also enrolled in this study as control.

There were no significant differences in detection thresholds (2.2 vs. 1.4, P=0.13), recognition thresholds (3.9 vs. 3.5, P=0.39) and OE (4.8 vs. 4.2, P=0.47) between PVOD and PD, while VAS scores of PVOD and PD were significantly different (2.0 and 6.2, P<0.01). In OE, significant differences were observed in the accuracy rates of menthol (68% vs. 44%, P=0.04) and Indian ink (42% vs. 15%, P=0.01) between PVOD and PD. Of particular interest, patients with PVOD tended to select "no detectable," while patients with PD tended to select wrong alternative other than "no smell detected."

Discrepancy between VAS and OE, and high selected rates of wrong alternative other than "undetectable" in OE might be significant signs of olfactory dysfunction associated with PD.