R. Edwards et A. Beuter, SENSITIVITY AND SPECIFICITY OF A PORTABLE SYSTEM MEASURING POSTURAL TREMOR, Neurotoxicology and teratology, 19(2), 1997, pp. 95-104
A portable, accelerometric system measuring tremor was evaluated, That
is, the validity and consistency of measurements as well as its abili
ty to discriminate pathologic from physiological tremor were investiga
ted. Control subjects and patients with Parkinson's disease were teste
d with this portable system and with an independent system that gave p
recise displacement data using lasers. It was found that amplitude of
postural tremor as measured by the two systems differed significantly,
but further investigation revealed that this difference was due 1) to
the difference between amplitude of acceleration and amplitude of dis
placement, and 2) to changes in tremor over the time between tests, ra
ther than to any inaccuracy or unreliability in the portable system. T
he other characteristics of tremor reported by the portable system wer
e also valid and reasonably reliable in test-retest experiments, with
the exception of the ''harmonic index,'' which proved less stable. Mos
t of the reported characteristics were distributed differently for the
control group and for the patients with Parkinson's disease, but the
large overlaps between distributions would make diagnosis difficult wh
en tremor is not very pronounced. These results suggest that until bet
ter discriminating measures of tremor are available, tremor tests shou
ld be repeated and combined with other tests of motor function. (C) 19
97 Elsevier Science Inc.