Personalized pain assessment: What does ‘acceptable pain’ mean to you?

What ‘acceptable pain’ means may be different for everyone and dependent on the moment and the context. In this text, we explore the concepts of pain acceptability and acceptance. We explain why we need to better explore (un)acceptable pain, to eventually facilitate pain assessment and management.


| INTRODUCTION
What does 'acceptable pain' mean to you? The question seems simple, but the answer may differ between people with painful experiences and may depend on contextual factors. While the definition of pain has been discussed in detail during the last decades, when pain can be considered 'acceptable' merits specific discussion. In this context, 'acceptable' may include 'tolerable' or 'satisfactory'; but may also be different for everyone, depending on the moment and the context. Pain acceptability may be distinct from manageability, and may precede, follow and/or inform the 'pain acceptance' process.
For the clinician, while intensity and functional status can be scored, the multidimensionality and subjective experience of pain can make it very complex to comprehensively appraise and state if one pain is 'acceptable or not' (Osborn & Rodham, 2010). This matters as pain assessment guides pain management. If pain is 'acceptable', this may mean that treatment with potentially serious consequences (especially adverse events) may not be desirable. As this scenario is frequent in pain management, this implies that exploring what acceptable pain might mean for people with painful experiences may have implications for pain management strategies.
Tools have been developed to assess pain, and scores to aggregate assessments (Bačkonja & Farrar, 2015;Pembrook, 2003). Although important and valuable, all tools are surrogates and are not interchangeable. While there is an important literature on how to use tools and scores in pain management and research, no published guidelines or guidance mention what 'acceptable pain' may mean.
In this text, we would like to highlight the importance of the concept of pain acceptability, the (only partial, if any) overlap with pain acceptance and why it may guide pain management. We will review the existing literature and explain why we need more research on what defines (un)acceptable pain, to eventually facilitate pain assessment and management.

DISTINCT TO 'MANAGEABLE PAIN'
What 'acceptable pain' means is an everyday question. For a nurse in recovery room after surgery, it may mean 'no need for more morphine'. For a physiotherapist in the ward, it may mean 'the patient can cough'. However, for people, in acute, but especially living with chronic pain, it may be distinct to 'manageable pain'. Sometimes, 'manageable pain' may not be acceptable, highlighting the importance of a multidimensional assessment of pain, but not only focussed on functional aspects. An anecdotal example is Waddel's observation (Waddell, 2004) that back pain was found to cause very little disability for Omani residents when, in Western society, back pain was (and remains) one of the most common reasons for sickness absence and unemployment (Lallukka et al., 2018;Waddell, 2004). Perhaps, back pain for people in Oman was somehow more manageable than for individuals living in North America and Europe. However, when Waddell (2004) introduced an orthopaedic clinic in Oman, they needed 'locks and guards on the clinic doors' as 'demanding' adults were flooding the clinic. This means that while pain was possibly manageable in enabling individuals to function without much disability, perhaps it was still (at least partially) unacceptable as individuals still sought out treatment from the new clinic. This (potential) fundamental distinction between 'acceptable pain' and 'manageable pain' raises an important question concerning what the term 'acceptable pain' is understood to mean.

ASSESSMENT: THE EXAMPLE OF RATIONAL PRESCRIBING
It is essential to understand what determines the 'acceptability' of pain. If, for the clinician, it might be mostly driven by functional aspects (manageability), which can be easily scored, it is not necessarily the case for patients. Let us take the example of rational prescribing, defined as 'making a diagnosis, estimating prognosis, establishing the goals of therapy, selecting the most appropriate treatment and monitoring the effects of the treatment' (Maxwell, 2016). In this context, a patient-centredpersonalized-rational prescribing should be painspecific (diagnosis), goal-oriented (prognosis modifying, goal-directed and monitored) but also integrate patient's perspective (appropriateness).
This implies that when we 'estimate prognosis' and try to predict the time course of return to an 'acceptable' pain level, it is not surprising that pain catastrophizing (potentially associated with a perceived high risk of unacceptable outcome) is associated with higher analgesic consumption, if analgesics are presented or perceived as a potential solution (Elphinston et al., 2022). Understanding what 'acceptable pain' may mean could help identify what might be an appropriate management. This is essential because, if pain can be deemed to be more 'acceptable' with a treatment, such treatment could be seen as appropriate. Conversely, in situations where we cannot achieve an 'acceptable' level of pain intensity with conventional interventions, the patient may benefit from more information before deciding how appropriate the interventions are. An example is the situation of opioid prescribing, notoriously not associated with significant improvements in chronic pain, and possibly associated with serious adverse events. In this typical situation, even if the pain was considered unacceptable, opioids are unlikely to be appropriate. This means that strategies other than medical interventions should be explored to help people deal with 'unacceptable pain'.

APPROACHES
It is common practice to assess pain using intensity rating scales and to determine acceptable cut-offs (Bačkonja & Farrar, 2015;Pembrook, 2003). While the utility and validity of pain intensity rating scales has been established, they are insufficient to appraise the acceptability of pain, as part of a comprehensive assessment of pain and factors influencing pain perception (Haefeli & Elfering, 2006). For instance, the subjective and multi-dimensional nature of pain means that pain can be difficult to quantify (Osborn & Rodham, 2010). Moreover, healthcare professionals reported different understandings of the meaning of the scores generated by these scales (Hodgins, 2002). Consequently, using cut-offs based on numerical scales, like 4/10, but also other kinds of indicators, to appraise need or success of pain management approaches may neglect important aspects of an individuals' pain experience (Yessick et al., 2022).

LITERATURE TELL US?
To identify the available evidence, gaps and needs in the area of research pertaining to the acceptability of pain for people living with chronic pain, we conducted a scoping review. In short, searching PubMed/MEDLINE and Cochrane Central Register of Controlled Trials (CENTRAL) using keywords such as 'pain' and 'acceptable' (see the Data S1 for the full methods and results). We only found one study, by Zelman et al. (2004), who explored features of a manageable/tolerable day for people with chronic pain, and described what individuals consider to be a desirable outcome when they use their pain medication. The study included people with three types of painful conditions (cancer pain, osteoarthritis and low back pain), exploring what a manageable day may mean, especially in terms of capacity to focus on something other than pain, to perform daily tasks and be active. Unacceptability was also explored in the Zelman et al. (2004) study (Table S1). In this study, 'acceptable pain' was considered inappropriate by participants, as it did not address the significant challenges associated with living with chronic pain in their lives. Therefore, the concept of 'acceptable pain' was abandoned and that of 'manageable day' was explored. A 'manageable day' included the ability to accomplish different tasks. On the other hand, 'unacceptable days' included physical, social or emotional impairments, as well as medication side effects (Data S1). While this can be taken as a positive definition of what 'unacceptable pain' can mean, it does not mean that pain without these impairments was considered 'acceptable', which leaves us with an open question. This gap was partly filled by the analysis of Thorne and Morley (2009) looking at 'How much change is required to achieve an acceptable outcome'. However, they looked specifically at magnitude of change and prospective judgement if pain would 'not have completely stopped'. This is only possible if we assume that pain was not acceptable at the beginning and will be acceptable at the end. This is not obviously always the case. The authors also found a 'large magnitude of acceptable change estimates' and that 'participants' judgements are not based on absolute criteria', challenging quantitative assessments. In a literature review, Moore et al. (2013) considered pain treatment (acute and chronic) acceptable only if 'achieving adequate pain relief', defined as 'no worse than mild pain' and associated with improvements in other symptoms of quality of life. While a noble intention, this claim is ambitious, focusses on change, is not always achievable and again assumes that pain is never acceptable at the beginning.
Consequently, these limited results indicate that there is a need for studies exploring acceptable pain in people with pain, especially qualitative studies exploring the subjective experiences of individuals.

| PAIN 'ACCEPTABILITY ' AND 'ACCEPTANCE' ARE NOT THE SAME
In this single study exploring what individuals with chronic pain consider to be acceptable and/or unacceptable, most participants rejected the idea that pain may be acceptable, even when articulating acceptability, disability and manageability (Zelman et al., 2004). This challenges the promotion of pain acceptance, and highlights that we still know very little about what acceptable pain means to people with pain. However, it is important to note that pain 'acceptability' and 'acceptance' are not the same.
Pain acceptance can be defined as 'the process of giving up the struggle with pain and learning to live life despite pain ' (LaChapelle et al., 2008). Different facets of pain acceptance have been described, including activity engagement, pain willingness and thought control. Pain acceptance appears to be more attitudinal, being an 'in the moment' response of openness, and potentially linked to the context, than an aspect of pain, like intensity and duration are (McCracken et al., 2004). It is now recognized that chronic pain acceptance and/or tolerance significantly influences an individual's pain perception. For instance, chronic pain acceptance has been found to be associated with reduced pain, psychological distress and physical disability (Haefeli & Elfering, 2006;McCracken et al., 2004;Vowles et al., 2008). Existing literature on the acceptance of chronic pain highlights that when an individual's expectations of their pain are not aligned with reality, their satisfaction and, therefore, quality of life can also be affected (Geurts et al., 2017;LaChapelle et al., 2008). But if, as often, pain cannot be realistically suppressed, expectations may change over time. This, therefore, highlights the importance of qualitatively exploring what individuals with pain may consider to be acceptable and/or unacceptable while living with their condition, and to what extent this is modifiable. This could be different from patient to patient, depending on conditions, associated with manageability or not, and aligned or not with clinicians' perspectives. What is clear is that the knowledge gap identified in the literature warrants future work in this direction, including, for instance, to what extent 'pain acceptability' may precede, follow and/or inform the 'pain acceptance' process in the patient's journey, and to what extent, like pain acceptance, pain acceptability may be more contextual that an aspect of pain.

| CONCLUSIONS
Very little is known concerning what 'acceptable pain' may mean to people living with pain. Qualitative studies may improve idiographic understanding of how individuals perceive and make sense of 'acceptable pain'. Even if not knowing all the determinants of what 'acceptable pain' may mean to a particular person and, potentially, regarding a specific treatment or other contextual aspects, it is important to consider the fact that perceptions, perspectives and expectations are fundamentally personal, and possibly not aligned with clinician's ones. Currently used scores and quantitative measures to assess pain intensity, not integrating essential aspects of the subjective human experience, may not be sufficient in to appraise pain acceptability.

CONFLICT OF INTEREST STATEMENT
PF received speaker/advisory board fees from Grunenthal and Oncomfort. The other authors have no conflict of interest.