Ryan Steven D’Souza, Mayank Gupta, Alaa Abd-Elsayed The assessment of pain is complex and challenging. It is crucial that clinicians and researchers use validated instruments in the assessment of pain-related outcomes. Given the multifaceted and complex nature of pain, there is no one single measure that captures the pain experience. Instead, scales that measure pain intensity, pain quality, psychosocial impact, emotional functioning, and physical functioning can be used. In this chapter, we review the most commonly used pain assessment tools in both the clinical and the research setting. Pain intensity is one of the most common aspects of pain that clinicians and researchers ask patients to rate when measuring pain-related outcomes. Although reliability and reproducibility may vary at different times in the same patient, the ease, speed, and importance of a measure of pain intensity when assessing outcomes highlights its relevance. Self-report scales are the most frequently used type of pain intensity scale. These include the numeric rating scale (NRS), visual analog scale (VAS), verbal rating scale (VRS), and other self-report scales (e.g., pain drawing measures). The NRS can be presented in an oral or written format, and patients are asked to rate their pain on a scale of 0 to 10, with 0 signifying no pain at all and 10 signifying the worst pain imaginable.1 Sometimes, ranges of 0 to 20 or 0 to 100 are utilized. Although there is no consensus on clinically significant changes, some consider a 2-point decrease on the NRS to be a clinically significant change in pain intensity.2 The major advantages of the NRS are that it is quick and easy to administer and has a very high completion rate among respondents.1 Similar to the NRS, the VAS employs a quantitative method of rating pain intensity. It utilizes a 10-cm line with end points signifying no pain at all at one end (0 cm) and the worst pain imaginable at the other end (10 cm). Patients place a mark at a point along the line that characterizes their pain intensity. Lower completion rates are seen with VAS scales compared with NRS scales.3,4 The VRS includes a list of descriptive words to grade pain intensity. Lists may have from 4 to 15 descriptors, and these descriptors may be assigned a value. The following is an example: 0 = no pain, 1 = mild pain, 2 = moderate pain, 3 = severe pain. Similar to the NRS, this scale is quick and easy to administer and complete, although it may be harder to administer to patients with limited vocabulary or literacy comprehension.5 Pain intensity scales using images may also be presented to patients. With these, the patient is asked to indicate the level of pain they are experiencing based on pictures of different facial expressions. These were developed for use with children, as well as with patients with low literacy levels. One example is the FACES scale that presents six different drawings of faces that represent six levels of pain intensity. The “very happy” face represents a score of 0, whereas the “very upset and crying” face represents a score of 10. Concerns regarding the use of this scale include that ratings may be affected by emotional reactions, and interpretation of the scales may vary between people and is affected by age, literacy, and culture.6,7 There are many types of patient to whom self-report pain intensity scales cannot be administered. These include pediatric patients who are not capable of using self-report measures, critically ill patients who are unable to communicate (e.g., intubated), and other patient populations. The inability to self-report pain does not exclude the possibility of its presence. In these settings, clinicians and researchers should utilize validated behavioral measures to assess behavioral indicators of pain intensity. One example of a behavioral scale is the Face, Legs, Activity, Cry, and Consolability (FLACC) scale that assesses postoperative pain in children.8 On this scale the five behaviors that are present in the title of the scale are rated, with each component rated on a 0 to 2 scale, with the maximum total questionnaire score being 10.8 Although grading pain intensity is helpful in assessing the severity and extent of pain, other scales that provide a more in-depth measure of the quality and affective components of the pain experience are often useful. These can further help the clinician or researcher assess how the pain experience is impacting the patient. The McGill Pain Questionnaire (MPQ) is a tool that assesses the quality and affective component of pain. Patients choose descriptors of the pain experience from 78 potential descriptors.9 These descriptors evaluate four separate domains: sensory, affective, evaluative, and miscellaneous. Patients also indicate the location of their pain on an anatomical drawing and provide details on alleviating and exacerbating factors. This questionnaire generates three scores: the Pain Rating Index, number of descriptor words chosen, and the pain intensity rating. This scale is widely used in the pain setting, and there is also a short version (15-item tool), the Short-Form (SF) MPQ.10 The tool has been validated through multiple studies, and its subscales are associated with patient quality of life, analgesic medication use, and sensitivity to pain treatment. Another facet of the pain experience is the behavioral and social aspect of chronic pain. Several validated instruments have been developed to quantify the pain experience across various social arenas, as well as in behavioral and interpersonal relationships. The West Haven-Yale Multidimensional Pain Inventory (WHYMPI) is a 52-item questionnaire that employs a 7-point Likert scale and is used to assess the psychosocial and behavioral aspects of the pain experience.11 The questionnaire is divided into three sections, with each section including several scales. The first section consists of six scales that measure pain interference in work and leisure activities, interpersonal relations, spousal support, pain severity and suffering, control over life, and negative mood. The second section measures the patient’s perception of the responses to their pain elicited from their significant other. These include solicitous responses, distraction, or negative responses. The third and final section assesses the frequency with which the patient performs daily activities such as household chores, outdoor work, and social events. There are three reliable profiles that can be characterized in patients with persistent pain after completion of this questionnaire: dysfunctional, interpersonally distressed, and adaptive copers. The Minnesota Multiphasic Personality Inventory (MMPI) is an objective tool to measure personality and psychological functioning.12 The most recent iteration of this scale, known as the Minnesota Multiphasic Personality Investory-2 Restructured Form (MMPI-2-RF), includes 338 items that yield scores on 3 higher-order scales, 9 clinical scales, 8 validity scales, 14 somatic and cognitive scales, 11 externalizing/interpersonal/interest scales, and 5 personality scales. The Patient Reported Outcomes Measurement Information System (PROMIS) is an initiative by the National Institutes of Health (NIH) to assess patient-reported outcomes in those with chronic diseases.13–15 These measures cover a wide range of domains, including physical, mental, and social health, across many different medical illnesses. Pain-specific measures that are also available in this initiative include a pain interference short form, and pain intensity and behavior measures. The pain interference form contains 41 items, with four short forms ranging from 4 to 8 items each. The pain behaviors form consists of 39 items and includes a short form that has 7 items. Studies have suggested that the PROMIS pain-related scales provide comprehensive and psychometrically sound measures of pain-related outcomes, although given the novelty and recent development of PROMIS, a limited amount of evidence of their validity is currently available. Chronic pain is a constant stressful state and commonly coexists with mood disorders. Research has highlighted that there is considerable overlap between chronic pain and depression-induced neuroplasticity changes and both share a similar neurobiological mechanism.16 Importantly, research has also highlighted that patients who deal with chronic pain–induced depression have a poorer prognosis than patients with chronic pain only.16 Furthermore, chronic pain and depression together can mutually promote the severity and progression of both. The Beck Depression Inventory (BDI) measures emotional functioning.17,18 This questionnaire consists of 21 items that measure the behavioral presentation of depression and assess depressive symptom severity over time. There have been two major revisions of the BDI, including the BDI-Ia and the BDI-II. The BDI-II has recently been used extensively in patients to evaluate for depression symptoms in settings with a high prevalence of pain.17,18 The Patient-Health Questionnaire-9 (PHQ-9) form consists of nine items that assess for the presence and severity of depression.19,20 Each item on the form is scored from 0 to 3, giving a total score ranging from 0 to 27. A cumulative score ≥10 indicates the presence of major depressive symptoms. The Generalized Anxiety Disorder-7 (GAD-7) form consists of seven items that assess for presence and severity of generalized anxiety.21,22 Each item on the form is scored from 0 to 3 giving a total score ranging from 0 to 27. Cumulative scores of 5, 10, and 15 signify mild, moderate, and severe anxiety symptoms, respectively. The Pain Anxiety Symptoms Scale (PASS) measures cognitive, physiologic, and behavioral components of pain related to fear.23 This questionnaire consists of 53 items that are categorized into the domains of fear of pain, cognitive anxiety, somatic anxiety, avoidance, and escape. Although studies have noted the high positive predictive value of the PASS for pain-related fear, it has been criticized for having poor predictive value for disability related to pain-related fear.24 The Medical Outcomes Study Short-Form Health Survey-36 (SF-36) measures a patient’s perceived health status.25,26 The SF-36 consists of 36 items that form eight separate scales including vitality, physical function, bodily pain, general health perceptions, physical role functioning, emotional role functioning, social role functioning, and mental health. The eight subscales are further combined and summarized into two domains: a physical component summary and a mental component summary. Cumulative scores range from 0 to 100, with lower scores indicating poorer health and quality of life. Although some patients may continue to experience similar pain intensity and pain quality despite procedural intervention, many will note an improvement in physical conditioning and functional outcome. It is not uncommon for patients to note that their pain intensity is the same, but that they now notice that they are able to walk for longer distances, perform more household chores or yard work, and engage more in social events. Thus it is crucial to also evaluate this component of the pain experience. The Oswestry Disability Index (ODI) is a common questionnaire used to evaluate functional outcomes and physical functioning in patients with acute or chronic low back pain.27 This questionnaire yields a subjective percentage score that grades the level of physical function or disability. The cumulative score indicates the patient as functioning at a point on a range from minimal disability to bedbound. The ODI questionnaire is more effective for patients with persistent severe disability, versus the Roland-Morris Questionnaire (discussed in the following section), which is indicated more for mild to moderate disability.28 The Roland-Morris Disability Questionnaire (RMQ) consists of 24 items that measure the degree of disability in patients with low back pain.29,30 These items focus on physical activity, sleep, psychosocial features, household management, eating, and frequency of pain. The cumulative score can range from 0, indicating no disability, to 24, indicating severe disability. In certain circumstances, interventions may provide transient but not long standing relief. These may help with pain intensity, quality of life, emotional functioning, and physical functioning in the short-term, but the effects may not persist as disease and degeneration progresses. Many patients will claim that despite the effects of interventions wearing off and relief being transient, they are globally satisfied about receiving the intervention. The Patient Global Impression of Change (PGIC) questionnaire reflects patient satisfaction and patient impressions regarding the efficacy of treatment or intervention.31,32 The questionnaire is graded by a 7-point scale on which patients rate their change as very much improved, much improved, minimally improved, no change, minimally worse, much worse, or very much worse. The Brief Pain Inventory (BPI) consists of 15 items and measures pain intensity and interference.33 Although this questionnaire was initially developed for the cancer pain population, it is now widely used for a variety of chronic pain presentations.34 Specifically, the questionnaire comprises pain drawings and diagrams, items regarding medications and analgesics, pain interference and intensity, relationships, mood, quality of life, and physical activities (sleep, general activity, and walking). Higher scores indicate greater severity and pain interference.33 This chapter outlines multiple validated questionnaires that span several domains to comprehensively and accurately capture the pain experience. Although certain domains may have greater relevance depending on the patient and provider, assessing pain outcomes through all domains is important, as outcomes are interrelated and impact one another.
Chapter 8: Measuring outcomes
Introduction
Pain intensity
Self-report scales
Behavioral scale
Pain quality
Mcgill pain questionnaire
Psychosocial impact
West haven-yale multidimensional pain inventory
Minnesota multiphasic personality inventory
Patient reported outcomes measurement information system
Mood and emotional functioning
Beck depression inventory
Patient-health questionnaire-9 form
Generalized anxiety disorder-7 form
Pain anxiety symptoms scale
Short-form health survey-36
Physical conditioning and functional outcomes
Oswestry disability index
Roland-morris disability questionnaire
Satisfaction
Patient global impression of change
Brief pain inventory
Conclusion
References
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