Following new approaches to chronic pain management, mechanism-based therapy is considered more effective than diagnosis-based treatment (Levin, 2004, Nijs et al., 2019a). Pain phenotyping is a challenging issue that seems to contribute to the provision of individualized rehabilitation and patient-centered care (Nijs et al., 2021a). So far, three mechanistic pain descriptors have been identified including the nociceptive, neuropathic and nociplastic pain. Nociplastic pain is the third mechanistic descriptor of chronic pain and refers to the pain resulting from the maintenance of central sensitization (CS) mechanisms (Trouvin, 2019). Research has shown that nociplastic pain leads to poor treatment outcomes when it is treated by targeting local structures’ healing (Nijs et al., 2019b). Early recognition of the mechanistic pain descriptors may result to be very important for the effectiveness of treatment, therefore, there is a great need to introduce such procedures to everyday clinical practice.
The forest and the trees…
Pain hypersensitivity has associated with CS in chronic musculoskeletal pain patients (Clark et al., 2017). Pain sensitivity usually is assessed with self-reported tools such as Pain Sensitivity Questionnaire (Ruscheweyha, 2009) and other sensory tests. Quantitative sensory testing (QST) is a battery of tests that checks the functioning of the somatosensory system and it provides an indication of pain sensitivity. Compared to laboratory tests, QST requires simpler equipment and enables the assessment of the small sensory fibers function. QST is applied using different stimuli and can provide information on the mechanisms of pain (Uddin and MacDermid, 2016). Dynamic QST such as Temporal Summation (TS) and Conditioned Pain Modulation (CPM) assess the function of endogenous pain inhibitory systems. (For more information, read the earlier published post http://www.paininmotion.be/blog/detail/quantitativ...).
Disadvantages of QST include the need of a rather expensive equipment, special training of the assessor and lack of standardized protocols and norms (Uddin and MacDermid, 2016). High-quality methodological studies are needed to evaluate the psychometric properties of QST (Bilika et al. 2022 submitted). Moreover, different factors (motivation, mood, menstruation) should be taken under consideration as they may influence the results of QST.
Because of the complex nature of pain, the management of patients with chronic pain should primarily be based on the evaluation of not only biological but also psychological, social, emotional and individual factors including the patient's beliefs, perceptions and expectations. Based on these data, the therapist can create an individualized treatment plan that is likely to benefit the patient significantly. Relying only to specialized tests or questionnaires is similar to "we cannot see the forest for the trees". If the patient is a "forest", a single tree cannot provide the overall view of the forest.
The 2021 IASP clinical criteria for nociplastic pain: Is there any gap?
In 2021, IASP announced the criteria (included in an algorithm) for identifying patients with chronic pain (Kosek et al., 2021). This new algorithm is a revision of a previously published algorithm (Nijs et al., 2014). The purpose of developing such criteria is to help clinicians in a simple way to identify cases of patients with nociplastic pain in order to provide the most appropriate treatment. Although this is an excellent step which gives an opportunity to a rather “forest” perspective, there are currently no studies on the reliability and validity of the IASP algorithm. This is an important issue that concerns the repeatability of the examiner's results but also the agreement between different examiners.
Let’s give food for thought!
Given the fact that there is not a gold standard for recognition of nociplastic pain, appropriate methods should be developed to evaluate new tools. An innovative method that has been used in social and health science, is the vignette methodology. Vignettes are scenarios based on real or imagined events, situations or persons. More precisely, a vignette presents a case study that a specific reader is called upon to evaluate. Recommendations have been given for the development of vignettes so that they are valid. This method could give insight for the evaluation of the reliability and validity of the IASP algorithm (Nijs et al., 2021b).
The first algorithm included four criteria (Nijs et al., 2014). First, the user should claim whether the patient's pain is neuropathic. The second criterion refers to the association between pain experience or disability and the extent of tissue damage or pathology. If there is a disproportionate relation, the criterion could be regarded as positive. Then, the user check for the pain distribution. A diffuse pain or a score above 40 on Central Sensitization Inventory declares the presence of CS.
We recently tested the reliability and validity of the first algorithm (Bilika et al. 2022 European Pain Federation Congress). For the purposes of the study, we developed vignettes, i.e., clinical scenarios of patients with and without clinical features that have been associated with CS. The vignettes were tested by two pain experts and modified accordingly to be as realistic as possible. They were then evaluated twice by four independent physiotherapists (with sufficient knowledge of the mechanisms of chronic pain). The results showed moderate to good intra-rater reliability (k=0.53-0.78) but poor to moderate inter-rater reliability (k=0.25-0.5). In fact, a criterion (Disproportionate pain experience) was particularly difficult for the raters. The conclusions drawn were that examiners may need to be trained before using the specific criteria. Also, more precision is needed in the wording of the criteria (Bilika et al. 2022). Α prospective evaluation of inter-rater agreement of routine medical records audits showed that the agreement can be increased with a periodic discussion between raters (Mafra et al., 2020). So, there is food for thought in this area!
Based on the above mentioned, our team is currently evaluating the IASP algorithm with the vignette methodology. The purpose of our study is to investigate the reliability and validity of the IASP algorithm but also to establish appropriate recommendations for its use.
Paraskevi Bilika PT, Msc, PhD candidate
Clinical Exercise Physiology & Rehabilitation Research Laboratory,
Physiotherapy Department, University of Thessaly
References and further reading