Timed tests in the clinical assessment of motor function in Parkinson's disease.

Abstract: The clinical evaluation section of the Core Assessment Program for intracerebral Transplantations (CAPIT) for Parkinson's disease (PD) was developed to standardize the clinical evaluation in cell transplantation trials, but also has been used in other therapeutic trials for PD. An important part of the CAPIT protocol is the standardized timed tests of motor function. In a recent revision of CAPIT, the Core Assessment Program for Surgical Interventional Therapies in Parkinson's Disease (CAPSIT-PD), the timed tests have been modified. There are some practical considerations that need attention when timed tests are used. They should be performed under the same circumstances with the patient in a defined condition and according to the same instructions from one time to another. Also, the examiner should not assist the patient, either directly or indirectly, by cueing. In addition to quantification of motor function as an outcome measure in therapeutic trials and other clinical research, timed tests also can be used for determining dopaminegic responsiveness in differential diagnosis of parkinsonism. Our experience is that timed tests are valuable quantitative and objective measures in scientific as well as clinical assessments of PD. Practical guidelines for and examples of these areas of use are provided.

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Parkinson's disease (PD) is a chronic progressive condition characterized by degeneration of dopaminergic neurons originating from substantia nigra pars compacta and innervating the striatum (i.e., the putamen and caudate nucleus). The result is a striatal dopamine deficiency with an imbalance in the basal ganglia motor circuit and dysfunctional cortical activation. This is believed to cause the movement disorder of PD, characterized by progressive poverty and slowness of movement (hypo- and bradykinesia, respectively), tremor, and rigidity. (1,2) The underlying etiology of PD has, however, yet to be identified.

Numerous clinical rating scales have been suggested for quantification and assessment of disease progression and the efficacy of therapeutic interventions. Of these, the Hoehn & Yahr staging, (16) the Webster scale, (26) the Columbia scale, (7) and the Unified Parkinson's Disease Rating Scale (UPDRS) (8) are the most widely used to date. A general concern when using clinical rating scales is their subjectivity; that is, the score is dependent not only on the motor performance of the patient but also on the examiner's interpretation thereof. More objective measures, such as the Postural-Locomotor-Manual (PLM) test, (25) have been developed. A major practical concern with such technical devices, however, is that they are relatively expensive and their use may require special location, equipment, and training.

The Core Assessment Program for Intracerebral Transplantations (CAPIT) was published in 1992. (19) The purpose of CAPIT was to establish international consensus on the assessment of PD patients enrolled in clinical cell transplantation protocols, so that results from different clinical trials could be compared and amalgamated. The aim was to make CAPIT simple, accessible, and easy for anyone to use, as well as comprehensive and objective. Since then, clinical assessment according to CAPIT has gained widespread acceptance and been applied to the assessment of patients not only in transplantation trials, but also in trials of other therapeutic interventions for PD, such as pallidotomy (3) and deep brain stimulation. (17) CAPIT includes recommendations for clinical assessments, patient selection criteria, the graft tissue, and brain imaging techniques.

The clinical assessment section comprises patient-derived "on/off" diaries, observations during regular medication, and single-dose levodopa drug challenges. The levodopa test includes assessments in the practically defined "off" condition (i.e., in the morning, [greater than or equal to] 12 hours after the last anti-parkinsonian medication and [greater than or equal to] 1 hour after arising), in the best "on" condition, and continual (every 20 minutes) monitoring of motor performance following the intake of an individually standardized single dose of levodopa (preferably equal to the patient's first regular dose of the day), until the patient has switched "off" again. These assessments are performed by means of the UPDRS and timed motor tests. The timed tests can be considered a more objective and quantitative complement to the motor examination section of the UPDRS. The timed tests in CAPIT are pronation/supination of the hands, finger dexterity, hand/arm movement between two points, and a walking test.

The CAPIT protocol has recently been revised to make it more suitable as a common assessment program for all neurosurgical interventions in PD, not just transplantation trials. The revised version is called the Core Assessment Program for Surgical Interventional Therapies in Parkinson's Disease (CAPSIT-PD). (6) Briefly, the revision comprises simplifications of the single-dose levodopa drug challenge, omission of the clinical observations during regular medication, and improved assessments of dyskinesias. Furthermore, neuropsychological assessments and health-related quality-of-life measures also have been added, and the "best on" condition has been redefined as "defined on." Two of the timed tests, pronation/supination of the hands and finger dexterity, have been omitted and the other two have been modified.

As a practical complement to the CAPIT and CAPSIT-PD protocols, (6,19) this article provides more detailed guidelines, recommendations, and suggestions for the use of timed tests as complements to other measures in the clinical assessment of motor function in PD. The usefulness of these tests in clinical practice also is addressed. Detailed instructions about other clinical motor assessments included in the CAPIT and CAPSIT-PD protocols are available elsewhere. (11,12)

Timed Tests

Although the timed tests are an objective and quantitative method of evaluation, there are some practical considerations that need attention to make them as reliable and valuable as possible. Instructions and practical considerations on how to perform the respective tests are provided below. The hand/arm movement and walking tests are described and discussed as they appear in the new CAPSIT-PD, (6) whereas the pronation/supination and finger dexterity tests refer to the original CAPIT protocol. (19)

* Pronation/supination of the hands is performed with the patient sitting in a chair, tapping first the palm and then the back of his or her hand against the ipsilateral thigh. When commencing the test, the patient is instructed to rest the back of his or her hand on the thigh. The time in seconds for 20 successive movement cycles, that is, tapping of the palm and back of the hand, is recorded.

* Finger dexterity is performed with the patient seated in a chair. The patient is asked to hold up his or her hand and tap his or her thumb with each finger, starting with the index finger and back again. The time in seconds for 10 successive movement cycles, that is, from the index finger to the little finger and back again 10 times, is recorded.

* The hand/arm movement between two points is performed with the patient seated in a chair with a table in front of him or her. The table should be of comfortable height, preferably no more than 15 centimeters above the patient's knees. The patient is asked to tap his or her index finger back and forth, laterally, between two points placed 30 centimeters apart on the table. The number of completed movement cycles, that is, moving the finger from point one, tapping the second point and moving it back to point one again, during 20 seconds is recorded.

* In the walking test, the patient is asked to walk 7 meters, turn around and walk back again. The number of steps, including turning around, and time in seconds are recorded. If freezing episodes occur, these should also be counted and recorded.

Practical Considerations

Motor performance in PD is often influenced by factors such as stress and environment. Therefore, in order to yield comparable results, tests must be performed under the same circumstances on each occasion and from one patient to another. The location and surroundings should be as calm as possible and the same or similar from one occasion to another. To allow firm interpretation of the results, tests must be performed during defined conditions (e.g., practically defined "off" and "on") or time points in relation to drug intake, using the same set of tests performed the same way at each occasion. If more than one examiner is conducting the tests, it is important to make sure that each one is performing them the same way. As always when assessing movement disorders, it is also advantageous to videotape the test sessions.