Experiencing Painful Osteoarthritis: What Have We Learned From Listening?

Gillian A Hawker

Disclosures

Curr Opin Rheumatol. 2009;21(5):507-512. 

In This Article

Which Measures to Use?

The subjective nature of pain in osteoarthritis has been a barrier to its quantitative evaluation.[42] However, over the last several decades, the sophistication with which osteoarthritis pain may be evaluated has increased substantially. This evolution has seen the move from generic health status measures to evaluate osteoarthritis pain, for example, SF-36 bodily pain scale,[43] to osteoarthritis-specific measures, for example, the Western Ontario McMaster Universities osteoarthritis Index, WOMAC,[44] which predominantly assess the impact of pain on activity limitations, to measures currently being developed specifically to evaluate the osteoarthritis pain experience.

In clinical practice as in research, pain is best evaluated using standardized questionnaires, whether interviewer-administered or patient self-complete. A recent review by MacKichan et al.[45•] provides a summary of commonly used measures of pain in osteoarthritis and other rheumatic diseases. For osteoarthritis, these include both generic pain measures, including the VAS[46] and numeric pain rating scale,[47] the MPQ,[40,48] and the SF-36 bodily pain scale,[43] and osteoarthritis-specific measures, in particular the WOMAC[44] (specific to hip and knee osteoarthritis) and the Australian/Canadian Hand Osteoarthritis index[49] (AUSCAN; specific to hand osteoarthritis) pain subscales. A number of other pain measures exist but have been less often applied to the osteoarthritis population.

However, recent research has raised concerns about the adequacy of these measures to evaluate pain in osteoarthritis.[13,17,45•] These authors have examined the osteoarthritis pain experience elicited through focus groups against the items and domains of existing osteoarthritis measures to assess the content validity of these measures for evaluation of osteoarthritis pain. French et al.[13] examined 11 existing valid and reliable pain measures. Most assessed pain characteristics or pain impact or both; however, of those that assessed pain characteristics, most evaluated only pain intensity. Only the Vanderbilt Pain Management Inventory,[50] as its name suggests, evaluated modifications made to manage pain and discussions of pain, whereas only the WOMAC pain subscale evaluated factors affecting pain. Stamm et al.[17] examined six osteoarthritis hand measures, including the Cochin,[51] AUSCAN,[49] and Functional Index for Hand Osteoarthritis,[52] and found that only pain location and relation to activity were well represented.

To address this gap, Hawker et al.[15••] have developed a new OMERACT/OARSI osteoarthritis pain measure, the Intermittent and Constant Osteoarthritis Pain instrument (ICOAP). The new measure comprises two subscales: one for constant pain and one for intermittent pain or 'pain that comes and goes'. Each subscale evaluates pain intensity, affect on sleep, impact on quality of life, the extent to which pain frustrates or annoys, and the extent to which pain causes worry or upsets. ICOAP is currently undergoing psychometric evaluation;[53] early evidence suggests this new measure is reliable, valid, and responsive to change.

Another newer measure for osteoarthritis is the osteoarthritis knee and hip quality of life instrument (OAKHQOL),[54,55] developed to address existing gaps in evaluation of health-related quality of life, HRQOL, in hip and knee osteoarthritis, documented through elicitation of the impact of osteoarthritis on HRQOL from interviews of osteoarthritis patients and health professionals. The OAKHQOL includes items that address many of the pain experience domains identified as important,[13,17] including the impact of pain on mood and sleep, frequency and intensity of pain, and discussions with others. However, OAKHQOL does not assess the nature or quality of the pain itself.

Regardless of the choice of measure(s), evaluation of the pain experience in osteoarthritis requires a 'bio-psychosocial' perspective, in which key contextual factors known to influence pain are also assessed, for example, mood, sleep and fatigue, coping style and self-efficacy, and social support. Standardized, valid, and reliable measures exist to evaluate these constructs,[56] and, depending on the intent of the pain assessment, these factors may also warrant evaluation.

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