Numeric rating scales (NRS) are popular subjective measures used to assess pain intensity. As pain is one of the most common medical concerns worldwide, effective measures and treatments become essential. Pain is a complex phenomenon which consists of multiple aspects, such as duration, intensity, and location. Although pain experiences vary between individuals and cultures, pain can result in physical disability, emotional distress, and financial problems. In fact, the costs of chronic pain in the US alone reach $550-625 billion per year (Danise & Turk, 2013). Nevertheless, the subjective nature of pain experiences challenges research and care, making subjective measurements valuable tools in pain management.
Numeric Rating Scales and Modes of Administration
Subjective measurements are beneficial tools to assess pain severity, quality (e.g., sharp pain), and impact on patients’ well-being. Numeric rating scales are among the most popular subjective measures used to evaluate pain. These scales are easy to administer and analyze, which makes them applicable across a wide range of settings (e.g., pediatric populations). Digital numeric rating scales, in particular, are attractive tools that have the potential to improve data collection, user experience, and interoperability. In fact, studies show that patients want to rate their pain experience, rather than simply opt for analgesia (Karcioglu et al., 2018). Thus, numeric rating scales and self-reports can help patients become active participants in medical decision-making and digital health.
Self-reports are valuable tools in medicine which empower patients and improve doctor-patient communication. In fact, as some symptoms cannot be directly observed or measured, only subjective measurements can help clinicians understand an internal event such as pain. Numeric rating scales, in particular, are among the most popular self-reports used to assess pain intensity in adults and children. Because of the simplicity of the numeric rating scale, such assessment is quick and easy to administer. Numeric rating scales can be administered verbally (e.g., over the phone), in writing, and digitally. When done verbally, the patient rates their pain, and the clinician records their score. When done in writing, the patient can give a single rating or select a number (within a given range) that fits their pain experience (e.g., five on a 0-10 scale).
The numeric rating pain assessment often includes an 11-point scale (0-10) in which patients rate their pain intensity. Note that “0” indicates “no pain at all,” while “10” “the worst pain imaginable.” Interestingly, these scales do not have ratio properties. In other words, if a patient rates their pain “10” that doesn’t necessarily indicate twice as much pain as a “5” score. Numeric rating scales can also constitute of 21 points (0-20) and 101 points (0-100) (Jensen & Karoly, 2001). Interestingly, Jensen and colleagues used a 1-100 scale on 124 patients and found that more than 90% of participants used the rating scale in multiples of five, which is an analog to a 0-20 scale.
With the increasing use of digital tools in health care, electronic numeric rating scales are slowly talking over pen-and-paper assessments. In fact, research shows that the electronic version of the numeric rating scale is preferred among pediatric populations (Castarlenas et al., 2015). The simplicity of the digital numeric rating scale facilitates data analysis, which can result in effective emergency care, pain management, and health outcomes. Digital rating scales are commonly employed in medical research and routine clinical care.
Psychometric Properties of Numeric Rating Scales
Psychometric Properties of Verbal Rating Scales: The verbal rating scale reveals good psychometric properties (Haefeli & Elfering, 2006). Usually, the selection of an appropriate measurement with high validity, reliability, and responsiveness is fundamental. Research shows that the verbal rating scale correlates well with other pain measurements. Compliance is also high as respondents must read the whole set of descriptors before they rate their pain experience. Although some experts assume that descriptors should provide interval level data, the interpretation of the scale varies between subjects and may be reduced to ordinal data level (Mutebi et al., 2016). Note that in ordinal scales, the order of the values matters, while the distance between each variable is not known (e.g., “unhappy,” “happy,” “very happy”). Interval scales, on the other hand, provide both order of values and significant differences between two variables (e.g., Celsius temperature). In fact, as the verbal rating scale is often interpreted as a categorical ordinal scale, results can be analyzed using non-parametric statistics.
Descriptors and Verbal Assessments: Descriptors allow patients to select a statement that fits their pain experience. Note that descriptors, composed of four or more verbal adjectives, can be assigned a numeric score to facilitate analyses. Interestingly, there’s high variability in the interpretation of the descriptors in the middle of the rating scale. Mutebi and colleagues (2016) showed that when it comes to five-point sets of descriptors, the following sets are interpreted with the least variation: a) “None”, “mild”, “moderate”, “severe”, “very severe”, and “not at all”; b) “A little bit”, “moderately”, “quite a bit”, and “very much”. Interestingly, the study team recruited 6,000 subjects divided into four groups: 1) subjects taking medications for pain and arthritis; 2) subjects prescribed medications for anxiety and depression; 3) patients with cardiovascular problems; and 4) patients with respiratory conditions. Results showed that demographic factors influence the interpretation of descriptors and verbal rating scales.
Digital Verbal Rating Scales: With the increasing use of technologies in health care, the electronic implementation of verbal rating scales is more than desirable. The development of digital verbal rating scales requires some special consideration regarding cognitive load and readability. In case experts implement interactive voice record (IVR) technology, the response choices must be entered in spoken format. Response options should be consistent, short, and presented before the entry value (e.g., “For ‘very much’ press 5.”). Consequently, responses should be confirmed by the subject (e.g., “You entered ‘very much,’ is that correct?”). For tablets and mobile devices, screen size, font size, and orientation (vertical/horizontal) should be considered. Note that the area on the screen that can be tapped to give a response should be identical for each response choice. Despite all the challenges in digital health software development, research shows that electronic and multimedia tools are preferred by patients worldwide.
Numeric Rating Scales: Benefits and Usage
With numerous advantages in practice, numeric rating scales have a wide range of applications in research and routine clinical care. Studies show that the numerical rating scale corresponds well with the perceived need for pain relief and patient satisfaction, especially in children. Note that when it comes to pediatric populations, faces scales can facilitate pain assessment. Faces scales are graphical tools that use pictures or even photographs of facial expressions to help patients assess pain (Safikhani et al., 2018). The faces pain scale-revised (FPS-R) is one of the most popular scales developed specifically for children.
Numeric rating scales also reveal good discriminative power for chronic and cancer pain. Note that as chronic pain is a major health concern worldwide, patients and clinicians should focus on effective pain management. Electronic pain journals, for instance, can help users track medication intake, pain duration, and interference with other activities.
As numeric scales require minimal language translation, their use is widely popular across cultures (Hjermstad et al., 2011). When it comes to language barriers and patients with limited English proficiency, numeric rating scales can help patients communicate their pain symptoms. Note that social expectations and acceptance of pain may influence patients and their pain experiences. On top of that, research shows disparities in pain treatment based on ethnicity, as well as gender. Research shows that racial and ethnic minorities receive less adequate care for both acute and chronic care. Gender bias can also lead to disparities between men and women. Studies showed that women with coronary bypass surgery were less likely to receive pain killers as compared to men. Numeric rating scales can help health professionals assess pain experiences and provide individualized and effective medical care.
Thus, with a wide range of benefits across various settings, numeric rating scales become powerful subjective measures in research and care; such scales are:
- Responsive measurements with good psychometric properties
- Easy to administer and analyze
- Applicable to different clinical domains
- Preferred by patients across cultures
Verbal Numeric Rating Scales in Pediatric Populations
Verbal numeric scales are common tools to assess pain intensity in both adults and children. The verbal numeric rating scale, in particular, is highly beneficial in pediatric populations. The verbal numerical rating scale (VNRS) is one of the most popular tools used to measure pain in children. As explained above, such assessments are easy to administer as no special equipment is required.
Interestingly, Tsze and colleagues concluded that the verbal numeric rating scale has good psychometric properties in pediatric populations. In a cross-sectional study, the research team recruited 760 children (4-17 years) to assess pain intensity (via the verbal numeric rating scale and the faces pain scale-revised) (Tsze et al., 2018). As explained earlier, faces scales are effective graphical tools which can facilitate pain assessment. The verbal numeric rating scale revealed high convergent validity, known-groups validity, responsivity, and reliability, particularly for children aged 6 to 17 years.
Note that convergent validity refers to the degree to which two tools designed to measure the same construct show the same results. Known-groups validity, on the other hand, refers to the degree to which a measurement can discriminate between different groups. Responsivity is also vital as it supports construct validity – or the degree to which the tool measures what it claims to assess. In fact, responsivity to anesthesia is an important factor in pain treatment and management. Last but not least, reliability is another vital psychometric property which represents the consistency of a test under similar conditions and over time.
Numeric Rating Scales and Subjective Measures: Conclusion
The numeric rating scale is one of the most popular subjective measures used to assess pain intensity. The scale reveals good psychometric properties and meets vital regulatory requirements for pain assessment. Numerical rating scales are easy to administer (even in emergency settings) as they do not require any special equipment. These scales are applicable across a wide range of domains and responsive to both chronic and acute pain. What’s more, research shows that numeric rating scales are preferred by patients worldwide. The verbal numeric rating scale, for instance, is a commonly used tool in pediatric populations (4-17 years) which can improve pain treatment and management.
As pain experience is a private event, pain intensity cannot be directly observed by experts or detected by laboratory tests. Thus, self-reports become paramount in research and practice. Subjective measures empower patients, helping them become equal partners in decision-making. Digital rating scales, in particular, improve data collection, user experience, and interoperability beyond borders. Such health care tools can improve pain treatment and management, by erasing gender bias and treatment discrepancies.
To sum up, pain assessment is a complex process. Pain is an internal experience which varies in quality, location, affect, and intensity. Cultural and social differences also have an impact on pain experience. Yet, as pain is a major health concern across the globe, researchers and clinicians should provide individualized and effective pain treatment. Numeric rating scales can help health professionals understand their patients and help them lead a pain-free life.
Rating Scales and Digital Health: Conclusion
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