The Centers for Disease Control and Prevention (CDC) guidelines for prescribing opioids for chronic pain have brought renewed attention to the field of pain management. Health care professionals who treat pain require objective measures that incorporate both emotional and sensory aspects of a patient’s pain experience. This is far from easy, however.
Pain is inherently subjective and could be considered an emotional response to a personal experience. In fact, emotional suffering is an important and perhaps underappreciated aspect of persistent pain.1 At the same time, pain is ubiquitous, familiar, and among the most common reasons for accessing the United States health care system.2
Acute pain tends to be more straightforward to quantify than chronic pain. Monitoring the time to reaction from various levels of noxious stimulation in an experimental setting can provide an objective measure for both humans and animals. Chronic pain, however, frequently lacks an apparent noxious stimulus. Measurements of such pain are typically based on a patient’s self-report or on clinical observations of the patient’s behaviors. Both may lead to unreliable results.3
The key to understanding pain evaluation tools is recognizing that acute and chronic pain are fundamentally different and not necessarily related. The proposed process of “algopathy,” for example, describes a continuum of pain from “an acute, adaptive, expected pain to a chronic, maladaptive, centralized pain.” This creates a multitude of changes in the neural-system perception of pain, in pain processing by the brain, and in the way patients perceive pain in an emotional context.4 In essence, algopathy outlines a transformation of acute pain into chronic pain and explains a mixture of both conditions.
Current Pain Metrics
Regular pain assessments are important components of chronic pain therapy. The ideal pain assessment tool would produce a numeric score or other objective metric, be easy to administer, be readily understood by patients, and yield reproducible results with good specificity and sensitivity. Many clinically tested and validated pain scales exist (for a full listing, go to https://www.practicalpainmanagement.com/resource-centers/opioid-prescribing-monitoring/list-clinically-tested-validated-pain-scales).5-29
The visual analog scale (VAS) is among the most frequently used pain scales in the US.30 With the VAS, clinicians ask patients to describe their pain by pointing to the most representative area along a line labeled “no pain” at its left end and “the worst pain imaginable” at its right end. For the Wong-Baker FACES scale, the best-known pediatric pain assessment tool, clinicians show children 6 faces—from a smiling happy face to a vigorously crying face—and ask which face best represents their current pain level.21
Pain manifests itself in numerous ways (eg, functional limitations, emotional symptoms, physical sensations, and behavioral changes), and clinicians should be careful to choose the pain assessment tool that most closely corresponds to a patient’s symptoms and conditions. This variation in functionality can cause confusion because pain scales are not interchangeable—a 10 on 1 scale may not be equivalent to the same score on another. What’s more, pain scales may measure not only pain intensity but also changes over time, functional limitations, emotional aspects, and behavior.
To establish these measures, pain scales rely on either patient self-reporting
or assessment by a health care professional (or a parent, family member, or caregiver in some cases). Self-reports may or may not be consistent over time but have been validated in many studies of pain assessments.
The language of pain is crucial to its reliable evaluation. Longer, more comprehensive descriptions of pain may be easier for a patient to grasp and categorize than pain descriptors, such as “moderate pain” or “pain that is getting worse.” It also may be clinically meaningful to evaluate pain not in terms of its intensity but rather in terms of how much and in what ways it interferes with function. For instance, being able to sit comfortably through a movie may be more relevant to a chronic pain patient than dropping 1 point on a numeric rating scale. Pain scales may further neglect emotional components of pain and symptoms of mental distress, such as depression, anxiety, and stress.
Despite laudable efforts to develop metrics that accurately and consistently measure pain levels over time, none of the many tools available achieve this task perfectly. For that reason, the Indiana Polyclinic Combined Pain Scale (IPCPS) was developed 15 years ago to offer the breadth required by certain chronic pain patients, the simplicity necessitated by a hectic clinical practice, and the versatility needed to accommodate a wide range of patients.
New Assessment Scales
The IPCPS consists of a combined pain scale, combined function scale, combined depression scale, and combined anxiety scale (see Tables 1-4, page 36-39). The new assessment tools, which were developed by the authors, attempt to account for the full spectrum of the pain experience and may provide a more accurate way of assessing and documenting chronic pain.
How IPCPS Measures Pain Intensity
The IPCPS rates pain intensity on the familiar 11-point scale, with 0 meaning “no pain” and 10 indicating “the worst possible pain imaginable.” Clear definitions of various pain states are more prominent than the scale’s numbers, however. With these added descriptions, along with examples, pain patients may be better able to contextualize and evaluate their pain intensity experiences.
Each patient completes the initial report without assistance from the health care team. During the appointment, the clinician then reviews the completed form with the patient (and any accompanying caregivers). Everyone is free to ask questions. Through discussion and clarification, the patient can gain an improved understanding of the pain intensity score and may revise the original report to eliminate unnecessary errors or inappropriately high or low reported scores. Because pain intensity can fluctuate in chronic pain patients, it is important for clinicians to frequently and consistently evaluate pain with the IPCPS.
Chronic pain interferes with function and can, in turn, affect patients’ well-being, independence, and ability to pursue the normal activities of daily living. One standard measurement of function is the Functional Independence Measure (FIM), an 18-item questionnaire that describes 13 motor functions (including eating, grooming, and bathing) and 5 cognitive functions (including expression, social interaction, and memory). Patients rate each function individually on a scale of 0 to 7.31 The higher the score, the better able the patient is to independently perform that task. The FIM scale requires that clinicians be trained in its use and observe the patients as they perform specific tasks.
The IPCPS uses a modified FIM scale, which allows it to work well for a wide range of conditions while remaining consistent with the IPCPS’s pain intensity scale. Instead of the original 0 to 7 scale, the modified FIM uses an 11-point scale, with 0 meaning “perfect function” and 10 indicating “complete disability.” Patients are also allowed to self-report their ratings rather than have a health care professional evaluate their performance. As with the pain intensity scale, each number is described in words so that the patients can contextualize their functional limitations.
Shame, guilt, humiliation, embarrassment, and mental defeat are categorized as “self-conscious emotions,” and are significantly more common among chronic pain patients than among control patients.32 Such self-conscious emotions can exacerbate pain intensity levels, and mental defeat is significantly related to disability.32 Catastrophizing also can worsen chronic pain conditions.33
Meanwhile, chronic pain patients asked to quantify their internal experiences can overestimate their depressive symptoms.34 In addition to items related to depression and anxiety in pain rating scales, validated assessment tools can be used to specifically measure such symptoms. However, these rating systems are sometimes complex or require a specially trained clinician to conduct them.35
Reporting depression and anxiety scores in a VAS format allows patients to be evaluated frequently over a period of time and can provide a series of scores that offer insights into symptomatology, pain progression, and treatment results.36 Because VAS scores are numerical, they can overcome literacy, linguistic, or cultural barriers that may arise when clinicians ask patients to describe their state of mind.37 Overall, VAS tests are simple to take, easy to administer, quick, inexpensive, and practical for busy real-world clinics with diverse patient populations.38
The Indiana Polyclinic team aimed to set the metric for the rating scale’s emotional component so that it could accurately classify depression and anxiety in a way that would allow patients to correctly and objectively self-report their emotional status. Although anxiety and depression are both mental health conditions that can impact pain, they require separate scales because they are fundamentally different states.
It is important to recognize that a diagnosis of major depressive disorder (MDD) does not require that patients feel depressed. Anhedonia along with other symptoms such as fatigue and decreased concentration suffice for an MDD diagnosis. For that reason, “joy of life” was added to the questionnaire to help better identify patients experiencing some degree of anhedonia.
Using the IPCPS in Practice
The IPCPS consists of 4 test instruments of similar design, each offering patients both verbal descriptions and numeric ratings. The experience of the Indiana Polyclinic over the past 15 years suggests that it’s most useful to administer all 4 tests to complex and chronic pain patients, even those who do not seem particularly depressed or who show no noticeable signs of functional impairment. While these test instruments may appear verbose at first glance, they become familiar after the first few uses. Patients can then rate these 4 aspects (pain intensity, function, depression, and anxiety) in a matter of minutes. The textual descriptions of the various ratings also may serve as springboards for more in-depth discussions about each patient’s experiences.
Further study is needed to validate the IPCPS and compare it with more established pain scales (all scales can be downloaded at http://indianapolyclinic.com/images/PainScales.pdf).
With the documented rise in adverse events, deaths, and disorders linked to long-term opioid treatment for chronic pain, it’s important that providers carefully select appropriate patients and subsequently monitor those who are at risk for opioid misuse.39-42
The risks and benefits of long-term opioid therapy for chronic pain management can evolve over time. Personal or family history of addiction is a common risk factor associated with potential abuse and addiction, while psychosocial issues as well as comorbid medical and mental health conditions may be dynamic factors.39 Therefore, continuous assessment is necessary.43,44
Combining several addictive medication classes increases the likelihood of abuse and addiction. The CDC guidelines specifically caution against concurrent prescribing of benzodiazepines and opioids due to an increased risk of morbidity and mortality associated with the combination therapy. When mixed with opioids, benzodiazepine exposure can increase mortality by 70%.45
Opioid-induced respiratory depression (OIRD) is the most serious possible complication of opioid use. The common risk factors of OIRD were identified in a cohort of Veterans Health Administration patients. To determine the probability of serious OIRD, the authors developed a 17-question survey called the Risk Index for Overdose or Serious Opioid-Induced Respiratory Depression (RIOSORD).46 Opioid dependence, psychiatric disorder, pulmonary disease, liver disease, use of an extended-release opioid, use of an antidepressant, use of a benzodiazepine, daily morphine milligram equivalents (MME), and recent hospitalizations or emergency department visits were all identified as relevant risk factors for OIRD. Each of these variables correlates with an average predicted probability of OIRD by incremental risk of 3% to 94%.
Beyond the risk of respiratory depression, benzodiazepine exposure has been associated with higher cardiovascular and suicide mortality.47 Accordingly, pain practitioners should collect relevant information and pay close attention to which medications are prescribed to which patients by other health care providers.
Researchers identified significant differences between chronic pain patients with and without a substance use disorder long ago, but clinicians paid little attention to such differences for many years.48 Many of the available risk monitoring assessments are intended for use before commencing long-term opioid therapy and predict the probability of future misuse. However, these assessments ignore the need to continuously monitor risks and benefits.40-42 Even those instruments intended for continuous monitoring are often specific to opioid misuse and fail to assess other potential risk factors, such as psychosocial changes, abuse of other substances, and presence of psychiatric conditions.42 Current Opioid Misuse Measure (COMM) is one of the very few tools intended for ongoing reassessment of a pain patient on opioids, but it still does not include assessment of tobacco, alcohol, or other substances of abuse.49
Aberrant drug-taking behaviors differ in their predictive validity for opioid misuse (see Table 5).50 The Screening Tool for Addiction Risk (STAR) was developed to check for potential aberrant behaviors in patients starting long-term opioid therapy.40 The STAR is intended for use prior to initiating long-term opioid treatment and accounts for various psychosocial factors as well as other substance-related risks.40 Some questions in the original STAR version limited continuous assessment of psychosocial factors, however. Other important questions pertaining to more serious aberrant behaviors are also missing.41
Thus, with permission from the STAR developers, the Indiana Polyclinic in Indianapolis created a modified version to account for changes that may occur during long-term opioid therapy, as well as for illegal behaviors. The STAR-IPC revision includes 15 questions, is easy to score, and takes less than 5 minutes to complete (see Table 6). When used in combination with other risk management strategies, it can help clinicians highlight potential risks, recommend changes in the level of monitoring practices, or justify referrals for addiction treatment or ceasing opioids altogether.
The STAR-IPC version has several limitations: It is not intended to be a lie-
detector test and should not be used without additional monitoring strategies such as drug screens, communication with other providers and the patient’s relatives, inspection of medical records, and drug monitoring programs. The revised version has not been validated and requires additional studies. It may be further improved by adding a question about the use of benzodiazepines.
Although each pain assessment tool has strengths and weaknesses, recent additions and updates may offer health care professionals more help in ensuring the proper management of chronic pain without needlessly contributing to the risk of long-term opioid misuse by their patients.
Acknowledgements: The authors wish to thank Jo Ann LeQuang and Scott de Long, who helped with editing and proofreading this manuscript.