Interpreting the Clinical Significance of Pain Questionnaires
Chronic pain is one of the most prevalent problems facing the health-care system today. Over 50 million Americans are affected by pain, creating enormous personal, societal, and financial hardships. Over 80% of all physician visits occur due to complaints of pain, and the Joint Commission on Accreditation of Healthcare Organizations (JCAHO) has mandated that pain be considered the fifth vital sign, in addition to blood pressure, pulse, temperature, and respiration.1 Healthcare costs due to pain are in the tens of billions of dollars annually.2,3 Chronic pain patients are five times more likely to utilize healthcare services,4 and direct medical expenses can exceed $90 billion annually for back pain alone.5 In addition, the consequences of pain include lost earnings, reduced productivity, and increased disability and workers’ compensation benefits.6 Given the enormous impact of pain, the United States Congress declared the Decade of Pain Control and Research, starting January 1, 2001.7
The assessment of pain and its associated effects is a central component of any clinical practice in pain management, from primary care to specialized tertiary rehabilitation settings. In conjunction with clinical interviews, practitioners use various psychometric instruments to assess chronic pain patients, including self-reported measures and clinician-rated scales. Using multiple instruments in combination—rather than relying on any single measure—to assess the efficacy of a given intervention helps to ensure adequate and comprehensive assessments. Over the years, a myriad of psychometric measures have been developed to aid in the assessment and treatment of chronic pain. However, assessments can become complex, onerous, and burdensome to patients as the number of instruments utilized grows. An over-abundance of administered measures may often complicate rather than clarify the assessment process. As new instruments are developed, each measure is individually evaluated, and psychometric properties such as reliability and validity are established. However, instead of the newly developed measures replacing those that are out-of-date or less efficient, most are simply added on to some previously established assessment protocol. Therefore, determining which of the various tests displays the greatest utility in evaluation and responsiveness to change is critically important. The purpose of this article is: (1) to provide practicing clinicians with an update on what are the newest trends in measuring change in pain which may be quite daunting, especially since they are in their “infancy”; and (2) to present a more “tried and proven” approach that can be currently used in everyday practice.
The increasing amounts of paperwork that most medical patients have to complete prior to any initial physical evaluation require clinicians to consider the issue of incremental validity, or the extent to which an instrument contributes additional useful and accurate information toward answering a clinical question.8 Although screening tools are helpful in many instances, they are not diagnostic in and of themselves. Ongoing debates persist regarding how best to measure outcomes, and what the targeted outcome actually is for the treatment of chronic pain. Patients’ self-reported pain and disability level, return-to-work rates, and level of functioning have all been offered as the most important outcome to consider.9
The importance of measuring the efficacy of treatments has become an increasingly focal issue as more diverse invasive and non-invasive treatments for chronic pain emerge, and policy-makers grapple with escalating costs. A growing number of assessment measures have been developed in attempts to validate such treatments. Specifically, patient-reported measures have gained greater acceptance in recent years.10 Indeed, a recent Draft Guidance published by several Federal departments and regulatory bodies emphasized the importance of scientifically documenting the psychometric properties of patient-reported measures.11 Research studies are constantly testing and re-testing various measures to prove or disprove their reliabilities and analyze their predictive validities. The reliability (i.e., the consistency of any measure over time) is crucial because measures are typically utilized to evaluate patients undergoing active and ongoing treatment over time. The issue of validity (i.e., the extent to which an instrument measures what it is purported to measure) is also vitally important. Instruments must also demonstrate sensitivity, or the ability to accurately classify patients. Meta-analyses have demonstrated significant inconsistencies in these domains when analyzing chronic pain studies.12 In addition, the statistical properties of any given measure do not necessarily guarantee the practical relevance of the results that it generates.