Pain has all the right components to discourage its measurement. Different from other senses for which objective external references are available (eg, sound, color, smell), pain is an intimate experience that cannot be calibrated against external yardsticks. That is, pain is as intimate and subjective a phenomenon as it can be, which can only be inferred in other subjects by indirect means that are highly prone to error and noise (verbal self-reports, behavioral patterns, facial expressions, non-specific physiological changes, and fuzzy neuronal activity patterns). The complexity of pain is further increased by modulatory factors that affect both its intensity and perception, such as the diversity of internal and external triggers, pain’s dependence on context and prior experience, and cognitive and physiological differences in the processing and evaluation of stimuli.
Despite the difficulty, pain must be measured. Few human endeavours can be more consequential than reducing pain in the world, particularly its most extreme manifestations. The measurement of pain can help identify those most in need, evaluate the effect of therapeutic interventions, and recognize important sources of harm. Widespread measurements of pain would also greatly contribute to guide public health interventions targeted at those medical conditions that impose the greatest burden of pain.
Given the challenges of directly assessing pain, several scales were developed to evaluate the intensity of pain perceived by human patients using self-reporting questionnaires. These instruments, such as the visual analog scales, the numerical rating scale, and the McGill questionnaire, find widespread use in clinical and research settings. However, while greatly useful to represent the perceived intensity of pain, these scales are not designed to capture two important dynamic elements of the pain experience: its duration and pattern of evolution. By not taking these elements into account, the assessment of the burden of pain experienced by individuals, or populations, is constrained, as are quantitative comparisons.
We developed a new operational framework for the description and assessment of pain, which we refer to as Pain-Track. This framework was initially developed for the assessment of pain in human patients, with a summary version recently published in BMC Research Notes. To facilitate and foster its use by clinicians and researchers, a user-friendly web application of the framework was also developed, which is freely available at https://pain-track.org.
The Pain-Track is based on the following elements: (1) the temporal evolution of pain, around which intensity and other attributes of pain (texture and anatomy), interventions (eg, analgesia) and clinical symptoms can be orderly placed; (2) the classification of pain intensity into four discrete levels, anchored on well-known scenarios that individuals can easily relate to; (3) a graphic interface for data entry and interpretation, where quantitative (intensity and duration) and qualitative (texture, anatomy, interventions) components of the pain experience can be registered, analysed and compared through an intuitive combination of graphic elements; and (4) the use of time spent in each category of pain intensity as a better approach to quantify the overall burden of pain endured by an individual, or by a population.
Below is a 3-minute video describing the approach.
