Performance Measures Aid In PAD Management

 By Alicia Ault 

WASHINGTON -- Use of validated functional performance measures is preferable to relying on patient reporting when determining walking ability and the effects of treatments in peripheral arterial disease, according to Dr. Mary McGrae McDermott.

PAD patients may underreport leg symptoms because they often restrict their activity to avoid experiencing those symptoms, said Dr. McDermott at a conference sponsored by the Society for Vascular Surgery.

Using functional measures such as the 6-minute walk test can substantially increase diagnostic and treatment accuracy, said Dr. McDermott, of the department of medicine, Northwestern University, Chicago. Each measure, however, has positives and negatives, said Dr. McDermott, who was lead investigator in the WALCS trial. That study used several performance measures, including the 6-minute walk test, repeated chair stands, a standing balance test, and a test of walking speed (Ann. Intern. Med. 2002;136:1-32).

One of the most often-used performance measures is the treadmill walking test, but some data suggest it might not mimic actual walking, Dr. McDermott said. And older patients may experience anxiety or balance problems that have an impact on results, she said.

A 6-minute walk test conducted in a corridor may be easier and more productive for older patients, according to Dr. McDermott. The test should be done in a 100-foot long hallway, with patients told to walk as far as they can during the 6 minutes. There should be no conversation during the test.

The 6-minute walk test was first shown to be reliable in a 1998 study (J. Amer. Geriatr. Soc. 1998;46:706-11). PAD patients show significantly increased rates of average decline in the test, compared with those without PAD, Dr. McDermott said. She and her colleagues have completed a study showing that 6-minute walk performance at baseline predicts mortality.

In addition to the 6-minute walk, clinicians should consider three other tests which measure leg strength, balance, and walking speed. Together, these additional diagnostics constitute the summary performance score (SPS). Each is scored on a 0-4 scale and is added to create a total score of 0-12.

The first component is the 4-meter walk test, which is conducted in a corridor with a stopwatch. Patients who do not walk regularly for exercise have the greatest decline in the 4-meter speed. The SPS also includes a standing balance test and time to arise five times consecutively from a seated position. Lower SPS scores are associated with a higher risk of death, nursing home placement, and a reduction in the ability to perform activities of daily living, she said.

Physical activity can be measured with a vertical accelerometer, which works best in activities that involve movement at the hip. The device is more accurate than a pedometer, said Dr. McDermott, who has conducted several validation studies of the Caltrac vertical accelerometer, made by Muscle Dynamics Fitness Network of Torrance, Calif. In the trials, PAD patients were given the beeperlike device to wear for 7 days, except when sleeping or bathing. Dr. McDermott and her colleagues found that PAD patients had much lower activity than non-PAD patients, and that the performance correlated with 6-minute walk test results (J. Am. Geriatr. Soc. 2001;49:747-54).

Several questionnaires might also be useful, including the Walking Impairment Questionnaire and the Peripheral Artery Questionnaire. Both can measure patient responses to therapy, said Dr. McDermott.