Introduction

Olfactory dysfunction is one of the most common non-motor symptoms of Parkinson's disease (PD). The association between smell identification ability and motor subtypes of PD is not uniform in previous studies. This study aimed to compare the odor identification ability among different motor subtypes of PD in Vietnamese participants.

Methods

Patients who were diagnosed with PD according to the International Parkinson's Disease and Movement Disorder Society 2015 Diagnostic Criteria and had normal cognitive function were recruited. Participants were divided into akinetic-rigid (AR), tremor-dominant (TD), and mixed (MX) motor subgroups using the Movement Disorder Society-Unified Parkinson's Disease Rating Scale (MDS-UPDRS) score. Olfactory identification ability was evaluated using the Vietnamese Smell Identification Test (VSIT) and the Brief Smell Identification Test (BSIT). Cognitive status was assessed using the Mini-Mental State Examination (MMSE). Age, age at PD onset, disease duration, smell identification ability, and cognitive function were compared among the three PD motor subtypes.

Results

The AR subgroup was the most common motor subtype (n = 164, 75.2 %), followed by TD (n = 39, 17.9 %), and MX (n = 15, 6.9 %) subtypes. Age, age at PD onset, sex, disease duration, and MMSE score were not significantly different between the three motor subgroups (all p > 0.05). The median (IQR) VSIT scores of AR, TD, and MX subgroups were 5.00 [4.00;7.00], 5.00 [3.50;7.00], and 5.00 [3.00;6.00], respectively. The median (IQR) BSIT scores of AR, TD, and MX subgroups were 6.00 [4.00;7.00], 5.00 [4.00;7.00], and 5.00 [4.50;7.00], respectively. The VSIT and the BSIT scores were not significantly different among the three motor subtypes (all p > 0.05).

Conclusion

Smell identification ability assessed in both the VSIT and BSIT did not differ across the three motor subtypes of PD.

Introduction

The Vietnamese Smell Identification Test (VSIT) has been validated in determining olfactory dysfunction in the Vietnamese population; however, its value in diagnosing Parkinson's disease (PD) has not been established.

Methods

This case-control study was conducted at University Medical Center HCMC, Ho Chi Minh City, Vietnam. The study sample included non-demented PD patients and healthy controls (HC) who were gender- and age-matched. All participants were evaluated for odor identification ability using the VSIT and the Brief Smell Identification Test (BSIT).

Results

A total of 218 HCs and 218 PD patients participated in the study. The median VSIT and BSIT scores were significantly different between PD and HC groups (VSIT, 5 (3) vs. 9 (2), P < 0.0001; BSIT, 6 (3) vs 8 (2), P < 0.0001). Using the cut-off of <8 for correct answers out of 12 odorants, the VSIT had higher sensitivity (84.4%) and specificity (86.2%) than those of the BSIT (sensitivity of 81.7% and specificity of 69.3%) for the diagnosis of PD. The area under the curve (AUC) value was greater for the VSIT than for the BSIT (0.909 vs 0.818). The smell identification scores were not significantly correlated with disease duration, disease severity, or LEDD (all p > 0.05).

Conclusion

The VSIT can be a valuable ancillary tool for supporting the diagnosis of PD in Vietnam. Olfactory dysfunction in PD was unrelated to the disease duration and severity. The VSIT can be applied to improve the accuracy of clinical PD diagnosis.

Background

Correct olfactory identification requires familiarity with the odor stimuli and is culturally dependent. Existing smell identification tests (SIT) are not culturally specific and may not be reliable in detecting hyposmia in all populations. This study aimed to develop a smell identification test suitable for Vietnamese patients (VSIT).

Methods

The study included 4 phases: 1) survey-based evaluation of the familiarity of 68 odors to identify 18 odors for subsequent testing (N = 1050); 2) smell identification test of 18 odors in healthy patients (N = 50) to determine which 12 should be included in the VSIT; 3) comparison of VSIT scores on 12 odors in patients with hyposmia (N = 60; Brief smell identification test (BSIT) score <8 and those with normosmia (N = 120; BSIT score ≥8) to establish the validity of the newly developed test; and 4) retest of the VSIT in 60 normosmic patients from phase 3 (N = 60) to determine test-retest reliability.

Results

As expected, the mean (SD) VSIT score was significantly higher in the healthy participants than in the hyposmic patients [10.28 (1.34) vs 4.57 (1.76); P < 0.001]. Using a cut-off score at 8, the sensitivity and specificity of the instrument in detecting hyposmia were 93.3% and 97.5% respectively. The test-retest reliability using the intra-class correlation coefficient was at 0.72 (P < 0.001).

Conclusion

The Vietnamese Smell Identification Test (VSIT) demonstrated favorable validity and reliability and will allow for assessment of olfactory function in Vietnamese patients.