Pain is a subjective experience that cannot be directly measured. Therefore, patient-reported outcome is one of the currently accepted methods to capture pain intensity and its impact on activities of daily living. This article focuses on five patient-reported outcomes that have been used to measure trigeminal neuralgia pain—Visual Analog Scale, numeric rating scale, Barrow Neurological Institute Pain Intensity Score, McGill Pain Questionnaire, and Penn Facial Pain Scale. Each scale is evaluated for its practicality, applicability, comprehensiveness, reliability, validity, and sensitivity to measuring trigeminal neuralgia pain.
Key points
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The subjective and multidimensional quality of pain makes it challenging to study and emphasizes that a patient’s perception of pain should be accepted as the most valid reporting.
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Patient-reported outcome (PRO) tools capture patient’s pain ratings in a structured and reproducible format that also allows patients to evaluate their current condition and treatment.
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The Penn Facial Pain Scale is a multidimensional pain scale that assesses facial pain intensity and facial pain interference with activities of daily living and facial-specific activities.
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A composite questionnaire that combines multiple PROs should address the six domains of the Initiative on Methods, Measurement, and Pain Assessment in Clinical trials.
Introduction
Pain is a personal experience—it is impossible for a person to understand or experience another person’s pain. Even patients who experience the same pain stimuli or interventions have wide variability of their pain ratings. Pain is also more than just a sensory experience; it has physical, emotional, and social implications. The subjective and multidimensional quality of pain makes it challenging to study and emphasizes that a patient’s perception of pain should be accepted as the most valid reporting. Patient-reported outcome (PRO) tools are an excellent way to capture those pain ratings because they provide a structured and reproducible format that also allows patients to evaluate their current health condition and treatment. PROs are instrumental for measuring pain because patients are the only source of information, clinical assessments may not parallel a patient’s actual pain or disability, and patients should be the ones to decide whether or not their clinical change is actually meaningful.
The purpose of this article is to provide an overview of different PROs that can be used to measure pain and outcomes in trigeminal neuralgia (TN). There are several scales that can be used to measure pain, and readers are encouraged to choose the most appropriate outcome measure. Although there are several different PROs that can be used, the main issue with evaluating treatment response and efficacy is the lack of a consensus on which scale to use and defined criteria for outcomes. With the availability of many treatment options for TN, which range from conservative pharmacotherapy to neurosurgical intervention with Gamma Knife radiosurgery (RS), percutaneous stereotactic radiofrequency lesioning (RFL), and microvascular decompression (MVD), it is necessary to develop a uniform process of measuring pain in TN to compare the outcomes of different treatments. The PROs discussed in this article have been evaluated for practicality, applicability, comprehensiveness, reliability, validity, and sensitivity to measuring TN pain in addition to adherence to the six domains outlined by the Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials (IMMPACT) ( Tables 1 and 2 ).
| Criteria | Description |
|---|---|
| Applicable | Content and emphasis of the measure are relevant and disease-specific |
| Practical | Minimal respondent and administrative burden |
| Comprehensive | Addresses multidimensional components of disease burden (physical, psychosocial, etc.) |
| Reliable | Acceptable test-retest, inter-rater, and internal consistency reliability |
| Valid | Criterion: accuracy of the measure compared with gold standard Construct: ability to measure what it intends to measure Content: measurement is representative of the construct it is intended to measure |
| Sensitive | Correctly identify patients with disease and ability to detect differences that would be considered significant |
| Domain | Recommended Measure |
|---|---|
| Pain | 11-Point (0–10) numeric rating scale (preferred) or categorical ratings (eg, none mild, moderate, severe) of pain intensity |
| Physical functioning | Multidimensional Pain Inventory Interference Scale Brief Pain Inventory |
| Emotional functioning | Beck Depression Inventory Profile of Mood States |
| Global improvement or satisfaction | Patient Global Impression of Change |
| Symptoms and adverse events | Spontaneous reporting of symptoms and adverse events with open-ended prompts |
| Participant disposition | Participant recruitment and progress information |
Introduction
Pain is a personal experience—it is impossible for a person to understand or experience another person’s pain. Even patients who experience the same pain stimuli or interventions have wide variability of their pain ratings. Pain is also more than just a sensory experience; it has physical, emotional, and social implications. The subjective and multidimensional quality of pain makes it challenging to study and emphasizes that a patient’s perception of pain should be accepted as the most valid reporting. Patient-reported outcome (PRO) tools are an excellent way to capture those pain ratings because they provide a structured and reproducible format that also allows patients to evaluate their current health condition and treatment. PROs are instrumental for measuring pain because patients are the only source of information, clinical assessments may not parallel a patient’s actual pain or disability, and patients should be the ones to decide whether or not their clinical change is actually meaningful.
The purpose of this article is to provide an overview of different PROs that can be used to measure pain and outcomes in trigeminal neuralgia (TN). There are several scales that can be used to measure pain, and readers are encouraged to choose the most appropriate outcome measure. Although there are several different PROs that can be used, the main issue with evaluating treatment response and efficacy is the lack of a consensus on which scale to use and defined criteria for outcomes. With the availability of many treatment options for TN, which range from conservative pharmacotherapy to neurosurgical intervention with Gamma Knife radiosurgery (RS), percutaneous stereotactic radiofrequency lesioning (RFL), and microvascular decompression (MVD), it is necessary to develop a uniform process of measuring pain in TN to compare the outcomes of different treatments. The PROs discussed in this article have been evaluated for practicality, applicability, comprehensiveness, reliability, validity, and sensitivity to measuring TN pain in addition to adherence to the six domains outlined by the Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials (IMMPACT) ( Tables 1 and 2 ).
| Criteria | Description |
|---|---|
| Applicable | Content and emphasis of the measure are relevant and disease-specific |
| Practical | Minimal respondent and administrative burden |
| Comprehensive | Addresses multidimensional components of disease burden (physical, psychosocial, etc.) |
| Reliable | Acceptable test-retest, inter-rater, and internal consistency reliability |
| Valid | Criterion: accuracy of the measure compared with gold standard Construct: ability to measure what it intends to measure Content: measurement is representative of the construct it is intended to measure |
| Sensitive | Correctly identify patients with disease and ability to detect differences that would be considered significant |
| Domain | Recommended Measure |
|---|---|
| Pain | 11-Point (0–10) numeric rating scale (preferred) or categorical ratings (eg, none mild, moderate, severe) of pain intensity |
| Physical functioning | Multidimensional Pain Inventory Interference Scale Brief Pain Inventory |
| Emotional functioning | Beck Depression Inventory Profile of Mood States |
| Global improvement or satisfaction | Patient Global Impression of Change |
| Symptoms and adverse events | Spontaneous reporting of symptoms and adverse events with open-ended prompts |
| Participant disposition | Participant recruitment and progress information |
Review of pain scales and patient-reported outcome measures
Visual Analog Scale
Format
The visual analog scale (VAS) is a simple, 1-dimensional (1-D) scale that measures pain intensity ( Fig. 1 ). It is a 10-cm horizontal line with word anchors on either end. The word anchors can be changed to represent different dimensions of pain. The anchors most commonly used in pain studies are “no pain” and “worst possible pain.” Specific points along the line can be labeled with intensity-denoting adjectives or numbers; the scale is then referred to as a graphic rating scale. Patients are asked to mark the point on the line that represents the intensity of their pain. The VAS score is determined by measuring the distance in millimeters from the left hand side of the line to the point where the patient marked the line. The scale requires special materials (pen and paper), vision, and dexterity.
Evaluation
The VAS has been widely used and is well validated, reliable, and internally consistent when used to measure the intensity of pain. It has been used in several studies evaluating different treatments of TN, including pharmacotherapy, Gamma Knife RS, RFL, and MVD. The VAS is comprehensive and also a form of cross-modality matching because it uses a direct scaling technique. Thus, results can be presented as a ratio rather than as an interval, which allows for more meaningful statements regarding pain magnitude. For example, when a group of patients have shown a change in pain intensity of 80 to 40, their pain has been reduced by half.
The major critique of the VAS is that a majority of patients have difficulty discerning pain intensity, distress caused by pain, and how pain affects their quality of life. Scores on the VAS are often affected by changes in functional status, emotional effects, physical limitations, and pain-associated symptoms. Therefore, VAS scores may not singularly represent pain intensity; they may actually be more representative of pain intensity and distress caused by the pain. Although the VAS score can be affected by many different aspects of pain, it only specifically addresses the pain domain from the IMMPACT recommendations. Another limitation of the VAS is its impracticality—it requires special materials (paper form and pen) and dexterity. Therefore, the scale can only be administered in person or mailed, and it excludes populations with limited dexterity and vision, such as the geriatric population. It cannot be administered over the telephone because it is a graphic measure of pain, but it does provide a continuous outcome variable, which can be useful for evaluation.
Numeric Rating Scale for Pain Intensity
Format
The numeric rating scale for pain intensity (NRS-PI) is a 1-D scale used to measure pain intensity ( Fig. 2 ). It is a series of numbers ranging from 0 to 10 or 0 to 100, where the 2 respective endpoints are “no pain” and “worst possible pain.” Patients are asked to rate their pain at the time of completing the scale by selecting the number that best represents their level of pain. There are also variations of the scale that ask patients to rate different categories and intensities of their pain, such as their pain at its “worst,” “least,” “average,” and “right now.” The NRS-PI can be administered in person or over the telephone; it does not require special materials, vision, or dexterity.
Evaluation
The NRS has been well validated, has demonstrated positive correlation with different measures of pain, and has shown sensitivity to treatments known to improve pain intensity. The NRS is also a practical tool and has been widely used in several chronic pain trials. Unlike the VAS, the scale does not require special materials, the scoring is intuitive, and it can be administered verbally or over the telephone. The NRS and the VAS have been compared in several studies, and although both scales have proved validity and responsiveness, the intuitive nature of the NRS and its ability to be administered both in person and over the telephone give it an advantage over the VAS.
One major weakness of the NRS is its lack of ratio qualities, meaning that when a group of patients has shown a change in pain intensity of 8 to 4, it does not necessarily mean that their pain was been reduced by half. The scale is also 1-D and only addresses the pain domain from the IMMPACT recommendations.
Barrow Neurological Institute Pain Intensity Score
Format
The Barrow Neurological Institute Pain Intensity Score (BNI-PS) is a composite pain scale that measures pain intensity with a score ( Table 3 ). This scale is complicated because it requires an assessment of 3 distinct outcome measures and only some of the possible combinations are listed as choices for the BNI-PS. The first outcome domain is pain intensity defined into 4 discrete choices: none, occasional, some, and severe. The second outcome domain is the use of medications categorized as either yes or no response. The third domain is a subjective assessment by the patient or the practitioner (not specified in the design) as to whether the pain is controlled and categorized as either a yes or no response. The scale has typically been administered on paper, but it has the ability of being completed verbally in person or over the telephone.
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