Quantification of motor slowness in Parkinson's disease: Correlations between the tapping test and single joint ballistic movement parameters.

The tapping test is used routinely for the quantification of drug effects on motor slowness in Parkinson's disease (FD). This test has not been validated previously using reference methods measuring kinematic parameters of movement. We compared and correlated modifications of the tapping score induced by levodopa with that of kinematic parameters of a single joint ballistic movement in 10 PD patients. Results demonstrate that the modification of the tapping score correlates with the bradykinetic, but not the akinetic, component of motor slowness in PD. Also analyzed are the sensitivity and specificity of different thresholds of the increment of the tapping score for the detection of modifications in amplitude, velocity and acceleration. Using a tapping score threshold of positivity between 10 and 20% of increase, the sensitivity and specificity to detect significant modifications in velocity is 100%.