Spontaneous ambulatory activity as a quantifiable outcome measure for rheumatoid arthritis

Are fibromyalgia patients as inactive as they say they are?

Both fibromyalgia and rheumatoid arthritis (RA) patients self-report similar disability. These diseases are viewed differently by the medical profession as one has ample evidence of tissue damage and inflammation and the other does not. We were interested to see if an objective measure produced similar results. Twelve patients with RA were matched with 12 fibromyalgia patients by sex, age, and Health Assessment Questionnaire (HAQ) score. The 24-h ambulatory activity of these patients was recorded using the Numact monitor. Statistical analysis was performed using independent group t test for the ambulatory activity data and Spearman's correlation coefficients for HAQ and total energy. There were no significant differences found between the two groups in terms of total activity. Other compared analyses for activity included the number of steps taken, vigor of steps, and time spent standing, which were not statistically different. The correlation coefficients of HAQ and total ambulatory activity for the fibromyalgia group were rho = -0.638 (p = 0.026). Patients with RA and fibromyalgia displaying similar levels of self-reported disability have objective evidence of similar levels of total ambulatory activity. There is a statistically significant correlation between self-reported and objective measurements of disability for the fibromyalgia patients. Either of these measures merits further study as outcome measures for fibromyalgia.

Using the Actigraph to measure physical activity of people with disabilities: an investigation into measurement issues

This study investigates measurement issues when using the Actigraph motion sensor to measure the physical activity of people with disabilities. Four volunteers with rheumatoid arthritis participated in the study. Activity levels were measured using the Actigraph over four consecutive weekdays. Activity counts were determined using Actigraph Standard Software. The daily percent of waking time spent at each intensity level was calculated and a weighted average calculated to determine a single daily measure of activity. The variability of measurement, over 1, 2, 3 and 4 days, was examined using these weighted and rolling averages. Activity counts were very low, with over 50% of waking time spent in the 'very low' intensity category, demonstrating a marked floor effect. Little variability (+/-0.11 counts/min) in the level of physical activity was found across 1-4 days. The limited variability (consistency across days) in combination with the floor effect indicates that a 1-day data collection period is adequate. The limitations of the Actigraph are thus related to the existing software options, which have been designed for people without rheumatoid arthritis. The Actigraph does not appear to be a sensitive measure in people performing very low physical activity.

Performance-based methods for measuring the physical function of patients with osteoarthritis of the hip or knee: a systematic review of measurement properties

OBJECTIVE

To systematically review the measurement properties (i.e. internal consistency, reproducibility, validity, responsiveness and interpretability) of all performance-based methods which have been used to measure the physical function of patients with osteoarthritis of the hip or knee.

METHODS

A systematic search was conducted in Medline, CINAHL, PsychINFO and Embase. Standardized criteria were applied to assess the quality of the clinimetric studies and the measurement properties.

RESULTS

Twenty-six performance-based methods were included: 13 walking tests, two stair-climb tests, one chair test and ten multi-item tests. Three out of seven multi-activity tests were tested for internal consistency and two were rated positively. Fourteen tests were tested for reliability and five were rated positively. The absolute measurement error (agreement) was assessed for 10 tests. Only one test received a positive rating. Fourteen tests were tested for construct validity. Only two tests received positive ratings. Responsiveness was assessed for 12 tests, but none of them received a positive rating. A lot of indeterminate ratings were given, mostly for small studies or non-optimal analyses.

CONCLUSION

Many more well-designed studies are needed to assess the measurement properties of performance-based methods. More importantly, however, before one can make a justified choice of a particular performance-based method, consensus is needed on what activities should be included in a performance-based test for patients with hip or knee osteoarthritis and which aspects of function should be measured.

Extraction and validation of a lower limb HAQ by comparison with objective measurement of ambulatory activity

OBJECTIVES

Both the Health Assessment Questionnaire (HAQ) and the measurement of spontaneous ambulatory activity are measures that can be used to evaluate disability in RA.

METHODS

A cross sectional survey was conducted of 105 RA patients where the HAQ was compared with ambulatory activity from the Numact monitor. Rank correlation was used to evaluate the relationships between activity and the complete and individual sections of the HAQ.

RESULTS

Correlation of activity with total HAQ produced significant results (r= -0.29 to -0.48). Correlation with individual sections showed the strongest association with "Hygiene", followed by "Activities", and "Walking". A lower limb HAQ was devised using these and the dressing and rising items.

CONCLUSIONS

HAQ and recorded activity measure different but related aspects of disability. Activity should be used if the ability to quantify the result outweighs the extra effort involved in the study.