Spotlight on olfactory dysfunction in Parkinson's disease

Figures & data

Table 1 Commercially available smell identification tests

Smell identification test	Description
University of Pennsylvania Smell Identification Test (UPSIT)	40-Item test comprised in four booklets, each containing 10 microencapsulated odors (scratch and sniff); available in 29 languages; existing normative data for men and women, as well as cutoff values for Parkinson’s disease.
Brief Smell Identification Test (B-SIT)	12-Item version of the UPSIT; cross-cultural test containing odors commonly known in most cultures; existing normative data; several versions available; version A only available in 10 languages; version B only available in English.
Modified Brief Smell Identification Test (MB-SIT)	Modified version of the B-SIT including intensity, pleasantness, and familiarity rating scales; available in English and Spanish.
Pocket Smell Test	A 3-item forced-choice test used as a screening tool. There are four different versions of the test depending on the odors included.
Quick Smell Identification Test (Q-SIT)	3-Item (chocolate, banana, and smoke) modified version of the Pocket Smell test. It has an additional option for indicating anosmia.
Sniffin’ Sticks (SS)	Pen-like devices, similar to the felt-tip pens, filled with an odorant. The cap is removed and the subjects smell the tip of the pen and then select a response from a multiple choice form (four options for each pen). The most common version includes 16 pens (SS-16).
Sniffin’ Sticks Screening Test (SS-12)	A 12-pen identification test used for screening purposes.
Sniffin’ Sticks Extended Test	This kit contains three modules: threshold test, discrimination test, and identification test. The threshold test has 48 SS.

Table 2 Role of olfactory dysfunction on cohort studies addressing subjects at risk of developing PD or prodromal subjects

Study cohort	Population	Objective	Role of smell testing
Parkinson’s Associated Risk Study (PARS)	Subjects aged >60 years without any neurological disorder	To evaluate specific tests as predictors for increased risk for PD	The initial test for these subjects is the UPSIT
Progression Markers in the suspected Pre-motor Phase (PMPP)	Individuals at high risk of developing PD were selected from the PRIPS and TREND cohorts	To monitor progression of the neurodegenerative process in subjects in risk, subjects with early PD, and controls	Hyposmia (assessed by the SS-12) was one of the inclusion criteria in subjects with documented substantia nigra hyperechogenicity
Parkinson’s Progression Markers Initiative (PPMI)	Five different populations: genetic cohort, de novo PD, control, SWEDD, and prodromal cohort	To verify progression markers in PD	For the prodromal cohort, subjects must have at least one of the following: hyposmia (assessed by the UPSIT) or RBD (assessed by polysomnography)
Prospective Validation of Risk Factors for the Development of Parkinson Syndromes (PRIPS)	Subjects aged >60 years without known PD	Early detection of incident PD in PD-free subjects at baseline	Subjects underwent a three-step evaluation: screening by age, screening for positive family history and/or hyposmia, and screening for substantia nigra hyperechogenicity
Tuebinger evaluation of Risk factors for Early detection of NeuroDegeneration (TREND)	Subjects aged >50 years with either one or several of the prodromal risk markers or none of these markers	To collect data of several prodromal phase biomarkers in subjects without PD or Alzheimer disease	Risk markers assessed include RBD, hyposmia (as assessed by the SS), and depression

Abbreviations: PD, Parkinson’s disease; UPSIT, University of Pennsylvania Smell Identification Test; SS, Sniffin’ sticks; SWEDD, Scan without Evidence of Dopaminergic Deficit; RBD, REM sleep behavior disorder.