ISO/PRF 13091-2

INTERNATIONAL ISO
STANDARD 13091-2
Second edition
Mechanical vibration — Vibrotactile
perception thresholds for the
assessment of nerve dysfunction —
Part 2:
Analysis and interpretation of
measurements at the fingertips
Vibrations mécaniques — Seuils de perception vibrotactile pour
l'évaluation des troubles neurologiques —
Partie 2: Analyse et interprétation des mesures obtenues à la pulpe
des doigts
PROOF/ÉPREUVE
Reference number
ISO 13091-2:2021(E)
ISO 2021
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ISO 13091-2:2021(E)
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Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms, definitions, symbols and abbreviated terms ....................................................................................................... 1

3.1 Terms and definitions ....................................................................................................................................................................... 1

3.2 Symbols and abbreviated terms............................................................................................................................................... 3

4 Treatment of vibrotactile perception thresholds .............................................................................................................. 3

4.1 General ........................................................................................................................................................................................................... 3

4.2 Mean value of repeated measurements ............................................................................................................................. 4

4.3 Test/retest variability of threshold measurements ................................................................................................ 4

4.4 Treatment of unresolved errors ............................................................................................................................................... 5

4.5 Treatment of suspected increase in test/retest variability .............................................................................. 5

5 Calculation of threshold shift .................................................................................................................................................................. 5

5.1 General ........................................................................................................................................................................................................... 5

5.2 Relative threshold shift .................................................................................................................................................................... 5

5.3 Reference threshold shift ............................................................................................................................................................... 6

5.4 Mean value of threshold shift ..................................................................................................................................................... 6

5.5 Tactogram .................................................................................................................................................................................................... 6

5.6 Consistency of threshold shifts ................................................................................................................................................. 7

5.7 Mean mechanoreceptor population threshold shift ............................................................................................... 8

6 Interpretation of vibrotactile perception thresholds and threshold shifts ............................................8

6.1 General ........................................................................................................................................................................................................... 8

6.2 Measurement error and statistical significance of observed VPTs ............................................................ 9

6.3 Measurement error and statistical significance of relative threshold shifts ..................................... 9

6.4 Vibrotactile perception thresholds for healthy persons ..................................................................................... 9

6.5 Deviations from the VPTs of healthy persons .............................................................................................................. 9

6.6 Physiological and clinical implications of changes in VPTs ...........................................................................10

Annex A (informative) Vibrotactile perception thresholds for healthy persons .................................................11

Annex B (informative) Implications of changes in vibration perception thresholds .....................................19

Bibliography .............................................................................................................................................................................................................................24

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This document was prepared by Technical Committee ISO/TC 108, Mechanical vibration, shock and

condition monitoring, Subcommittee SC 4, Human exposure to mechanical vibration and shock.

This second edition cancels and replaces the first edition (ISO 13091-2:2003), which has been technically

— The contents of Annex A have been updated to include studies of the vibrotactile perception

Any feedback or questions on this document should be directed to the user’s national standards body. A

Early detection of peripheral neuropathies in the upper extremities, which are often manifest as changes

in tactile function and hence changes in mechanoreceptor acuity, is of considerable interest. Such

neuropathies can occur as a result of disease, or of exposure to chemical or physical, neurotoxic agents.

With a suitable choice of measurement conditions, as provided in ISO 13091-1, separate responses

from the slow-adapting type 1 (SAI) and fast-adapting types 1 and 2 (FAI and FAII) mechanoreceptor

populations can be determined by using vibrotactile stimulation at different frequencies.

This document defines the analysis and interpretation of vibrotactile thresholds measured at the

fingertips according to the provisions of ISO 13091-1. Procedures for describing statistically significant

changes in vibrotactile perception thresholds are provided for the situation in which the threshold is

determined on a single occasion, as well as when the threshold is determined repeatedly.

This edition of ISO 13091-2 contains an updated analysis of the vibrotactile perception thresholds

for healthy males and females and provides reference thresholds for all frequencies specified in

Values for the vibrotactile perception thresholds of healthy persons, applicable to thresholds

The implications of observed changes in vibrotactile perception thresholds are considered in Annex B.

This document specifies methods and procedures for analysing and interpreting vibrotactile

perception thresholds and threshold shifts. Procedures for describing statistically significant changes

This document is applicable to vibrotactile perception thresholds determined at the fingertips

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

ISO 13091-1, Mechanical vibration — Vibrotactile perception thresholds for the assessment of nerve

For the purposes of this document, the terms and definitions given in ISO 2041, ISO 5805 and

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

person who, in the opinion of a qualified physician, is free from signs or symptoms of peripheral

neurological disease as determined by physical examination and other clinical or objective tests deemed

necessary to support the opinion, and who has not been exposed to a neurotoxic agent, vibration, or

persistent shift in threshold from the corresponding reference vibrotactile perception threshold

persistent shift in threshold from the corresponding value recorded previously for the same person at

the same fingertip and frequency, or equivalent frequency, using the same measurement method

prediction of the risk of disease, or symptoms, from the results of an objective test of some human

fraction (or percentage) of a population group in whom the presence of disease, or symptoms, can be

fraction (or percentage) of a population group in whom the absence of disease, or symptoms, can be

statistical measure of the chance of one human property or function observed in a person co-existing

ratio of the observed difference in threshold from a baseline of 150 dB to that of healthy persons of the

same age from the same baseline, summed for each measurement frequency, or equivalent frequency

Note 1 to entry: An increase in vibrotactile perception threshold, which is associated with a reduction in acuity,

will result in a decrease in the sensibility index from the value of unity for healthy persons.

ΔT(SAI. FAI or FAII) mean reference threshold shift for SAI, FAI, or FAII receptor population

ΔT(SAI. FAI or FAII) mean relative threshold shift for SAI, FAI, or FAII receptor population

NOTE Symbols using an uppercase T refer to thresholds expressed in dB (ref.10 m/s ). The equivalent

The information required for the reporting, analysis and interpretation of VPTs determined in

accordance with the provisions of ISO 13091-1 is specified in ISO 13091-1:2001, Clause 7. A subject's

VPTs are commonly measured on a single occasion. In order to be interpretable, it is necessary to know

the expected variability in the VPTs if the measurement were to be repeated on another occasion (e.g. a

Two situations are considered in this document. If the VPT of a subject is determined repeatedly at

the same fingertip over a period of several days, then the test/retest variability applicable to the mean

value of the observed VPTs, expressed in decibels, shall be the standard deviation calculated from the

observed VPTs when expressed in decibels. Alternatively, in circumstances in which it is not possible

to calculate a meaningful standard deviation from the measurements performed (e.g. when only a

single measurement is made of a subject’s VPT), then the test/retest variability of the observed VPT

shall be estimated for the measurement method employed. The estimate shall be based on repeated

If the VPT at a given stimulation frequency or equivalent frequency, f , is determined repeatedly at a

fingertip according to the provisions of ISO 13091-1, then the mean value of the VPT shall be calculated

as the mean of the observed VPTs expressed in dB (ref.10 m/s ), using Formula (1):

NOTE The mean VPT calculated from the arithmetic mean of observed VPTs expressed in dB (ref.10 m/s ),

as in Formula (1), is equivalent to the geometrical mean of the observed VPTs expressed in m/s .

If the VPT is repeatedly determined at the same fingertip of a subject on separate occasions (e.g. on

different days), then the intra-individual test/retest variability in threshold shall be calculated for this

subject. The test/retest variability, V( f ), at a given stimulation frequency or equivalent frequency, f ,

(calculated using Formula [2]) shall be expressed in decibels as one standard deviation from the mean

value of the VPTs, expressed in decibels, as determined by repeated measurements. If the VPTs, T( f )

, found by repeated measurements at a given stimulation frequency or equivalent frequency, f , are

where T( f ) is the mean of n repeated measurements expressed in dB (ref.10 m/s ).

Under circumstances in which it is not possible to calculate a meaningful standard deviation for a

subject (e.g. when only a single measurement is made of a subject’s VPT), then the test/retest variability

of the observed VPT shall be estimated for the measurement method used. The estimate shall be

derived from the standard deviation of VPTs determined at the fingertips of healthy persons using the

same measurement method. The standard deviation shall be based on at least 10 measurements of

VPT performed on separate occasions (e.g. 10 different days). The measurements shall be performed

in accordance with the provisions of ISO 13091-1, and the standard deviation, expressed in decibels,

shall be calculated from the observed VPTs expressed in decibels using Formula (2). The within subject

standard deviation recorded from three or more healthy persons at a given frequency, or equivalent

frequency, shall be used as the estimate for the intra-individual test/retest variability at that frequency,

Normal hormonal changes during the menstrual cycle induce changes of up to 20 dB in the FAII

receptor thresholds of females. When estimating the test/retest variability for the FAII thresholds of

females, that is, for VPTs at measurement frequencies of 100 Hz, 125 Hz and 160 Hz, this tendency for

the threshold to cycle should be taken into account. The threshold changes occur several days before

Under some circumstances, the examiner might believe that unresolved errors have occurred during

threshold measurements. Also, errors might have been introduced by conducting measurements on a

In these situations, analysis and interpretation of VPTs using the methods and procedures contained

in this document are only possible if additional information is obtained. A second set of measurements

shall be performed according to the provisions of ISO 13091-1 if it is believed that more reliable VPTs

may be obtained. The second set of VPTs shall be treated as described in this document.

NOTE If, at a single measurement site, the VPTs are determined at two or more frequencies, or equivalent

frequencies, mediated by the same mechanoreceptor population, then the consistency of the threshold shifts

calculated according to the provisions of 5.6 can be examined to confirm the presence of errors.

Under some circumstances, the examiner might believe that the test/retest variability applicable to

the measurement method is not applicable to a subject. The opinion might be based on the lack of

consistency in determining ascending and descending thresholds as described in ISO 13091-1:2001, 6.3,

In these situations, analysis and interpretation of VPTs using the methods and procedures contained

in this document are only possible if the variability applicable to the subject is established. A subject-

specific test/retest variability is established by conducting repeated threshold measurements on the

The interpretation of VPTs is facilitated by calculation of the change in observed threshold from a

predefined value. The calculation of threshold shift shall be performed for each frequency, or equivalent

frequency, and fingertip at which VPTs have been obtained according to provisions of Clause 4.

The relative threshold shift shall be calculated as the difference between two VPT values expressed in

dB (ref.10 m/s ), or the ratio of the two VPT values expressed in m/s , one being the observed VPT

and the other a baseline VPT. The two VPTs shall be obtained from the same fingertip of a subject using

the same measurement method and measurement frequency, or equivalent frequency. The relative

threshold shift, ΔT( f ) , at the j frequency, f , shall be expressed in decibels, and calculated at each

where the observed VPT at the j frequency, T( f ) , and the baseline VPT at the same frequency, or

The equivalent expression for the relative threshold shift calculated from thresholds expressed in m/s

NOTE The calculation of relative threshold shifts facilitates the identification of patterns of change in

tactile acuity affecting an individual. Determining relative threshold shifts has proved beneficial in situations

in which a known pathological, or repair, process is followed in an individual over a period of time. Under these

circumstances, the baseline VPT is usually the original VPT recorded on the subject.

The reference threshold shift shall be calculated as the difference between the observed and reference

VPT values when both are expressed in dB (ref.10 m/s ), or the ratio of the two VPT values expressed

in m/s . The reference threshold shift, ΔT( f ) , at the j frequency, f , shall be expressed in dB, and

calculated at each measurement frequency, or equivalent frequency, using Formula (5):

where the observed VPT at the j frequency, T( f ) , and the reference VPT at the same frequency, or

The equivalent expression for the reference threshold shift calculated from thresholds expressed in m/

NOTE The calculation of reference threshold shifts facilitates the identification of patterns of tactile

abnormality that are interpretable in terms of changes in mechanoreceptor or nerve function. An association

has been found between reference threshold shifts and symptom reports. Reference threshold shifts can be

If the threshold shift for a given stimulation frequency, or equivalent frequency, is determined

repeatedly at a fingertip under circumstances in which it is not expected to change, then the arithmetic

mean value of the relative, or reference, threshold shift shall be calculated from the threshold shifts

expressed in decibels. The mean relative threshold shift at frequency, f , expressed in dB, is calculated

The mean reference threshold shift at frequency, f , expressed in dB, is calculated using Formula (8):

A tactogram shall consist of a logarithmic plot of frequency, or equivalent frequency, on the abscissa

and threshold shift expressed in dB on the ordinate, as shown in Figure 1. The threshold shift can range

from, typically, −20 dB to 60 dB. The frequency ranges in which thresholds are mediated by different

NOTE 1 The frequency ranges at which VPTs determined according to the provisions of ISO 13091-1 are

mediated by the SAI, FAI or FAII mechanoreceptor populations are listed in ISO 13091-1:2001, Table 3.

A tactogram can be constructed for individual fingers, hands, subjects, or groups of subjects, and the

applicable values of the relative, or reference, threshold shifts shall be plotted as ordinates. Values at

different frequencies, or equivalent frequencies, for individual fingers, hands, subjects, or groups of

If the tactogram is for one or both hands of an individual, the threshold shifts for individual fingers shall

be identified by different symbols. Thresholds shifts for fingers on the right hand should be indicated

NOTE 2 It can be convenient to indicate the finger by a number within the symbol for the hand, or by different

If VPTs have been determined at a single measurement site at more than one frequency, or equivalent

frequency, mediated by a given mechanoreceptor population according to the provisions of ISO 13091-1,

then the consistency of the relative, or reference, threshold shifts may be examined. The consistency is

expressed by the difference in dB between the relative or reference threshold shifts for frequencies,