BS ISO 13091-2:2021 pdf download – Mechanical vibration — Vibrotactile perception thresholds for the assessment of nerve dysfunction Part 2: Analysis and interpretation of measurements at the fingertips 4.3 Test/retest variability of threshold measurements 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 j ), at a given stimulation frequency or equivalent frequency, f j , (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 j ) i , found by repeated measurements at a given stimulation frequency or equivalent frequency, f j , are expressed in dB (ref. 10 −6 m/s 2 ), then: where T(f j ) M is the mean of n repeated measurements expressed in dB (ref. 10 −6 m/s 2 ). 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 VPTs 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, or equivalent frequency (one-way analysis of variance). 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 and after ovulation. 4.4 Treatment...
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