APPENDIX THREE
Maximum Voluntary Isometric Contraction (MVIC) and Other Strength Measures

A. MVIC Strain Gauge Measurement:

Purpose:

As primary or secondary outcome variable of ALS clinical trial.
Can measure rate of disease progression via impact on muscle strength and may be predictive for survival (Further study is needed).

Selection of muscles to test

10 muscle groups (5 arm, 5 leg) recommended by Brinkmann et al (J Neurol Sci 1997). As data accrue, modification may be needed on the basis of future study (see below).

Clinical Evaluator (CE):

• Same person for the same patient.
• Motivated, intelligent, preferably physical or occupational therapist.
• Must meet reliability criteria.
• Need backup, similarly trained and tested.

Standardization, Training, Reliability, Variance

Same system in all centers. Agreed upon written protocol for the test. Training video. Brinkmann et al 1997 can serve as a starting point.

• Bring CE and back-up in for training at a centralized site or sites.
• Return to home site with video and set up locally.
• Test at least 5 subjects and assure competence before testing patients in a trial.
• Do reliability testing (CE and backup, same patient volunteer, two tests each).
• To begin to test patients within a trial, CE test-retest variability must be less than 10% (intra-rater and inter-rater) or equivalent conservative limit, expressed using other parameter.
• "Super-CE monitor" visits periodically the individual sites for Quality Assurance.
• Local validation testing (inter and intra-rater ) between visits at fixed intervals.
• Super-CE Quality Assurance Committee to monitor for ongoing problems and remedy promptly.

See more detailed recommendations in Hoagland et al (Muscle and Nerve 1997; 20:691-695).

Costs of MVIC

Costs (1998 US Dollars):

• Table + frame: $3000; Computer + strain gauge: $3000-5000.
  Total may come to $8-12,000
• Training the CE and backup, which involves flying to the session, spending the day (approx. $3000 for two)
• Super-CE visit for monitoring reliability ($1500)
• Approx. cost of each exam $150 per patient (Medicare allowable for 60 minutes of a PTs time)

Data Analysis

Standardization by normalization to reference ALS patient population (Andres et al, Neurology 1988; 38:405-408) or according to percent predicted value (National Isometric Muscle Strength (NIMS) Database consortium, Arch Phys Med Rehabil; 1996;77:1251-1255).

Surrogate for Survival?

Two direct pieces of evidence and one indirect piece of evidence to confirm the clinical impression that patients who progress faster die sooner, using MVIC measurements:

• Smith et al - (Muscle & Nerve, 1993;16: 624-633) rate of decline by MVIC strongly related to survival.
• Stambler et al (Neurology 1998;50:66-72) - MVIC decline unrelated, but study could not show relation.
• Armon et al (IAMNDA 1997 meeting abstract): One point MVIC as part of deriving linear estimate of rate of decline: highly related to survival.

Future Study:

Optimal muscle groups to use should be the subject of research:

1. Sample cervical region alone or cervical and lumbosacral regions?
2. Standardized panel vs. Select best / most testable / reliable from a group.
3. Those muscles with least variability.
4. Combine muscle groups with myotomal distribution?

Whether reliability testing on patients is better than testing on normals.

MVIC as a surrogate for survival requires further study.

B. Manual Muscle Testing

Background

Hasn't been evaluated as rigorously as MVIC in patients with ALS.
Has been evaluated in polyneuropathy with monoclonal gammopathy.
Was used in an FSH, DMD (steroid) study, and appeared to be comparable to MVIC (when looking at total scores).

Standardization

The MRC scale was transformed in those studies into a 10 point scale, which may be better than the original 5-point scale, which has been used in ALS studies.

If used - needs to be approached as a research tool.

Limited Information:

CE
Reliability/Variance
Time of day
Training/Technique
Monitoring
Costs - same as MVIC, minus cost of equipment
Purpose

Surrogate for Survival?

Riluzole 1 study - impact on survival and on MMT; Riluzole II study - impact on survival but not on MMT; Other studies - no impact on survival or in MMT.

Future Research

All items listed above

C. Hand Held Dynamometry

Electronic hand-held dynamometry supported by Brinkmann et al. 1997. Further reliability data needed.

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