Fibromyalgia, also known as fibromyalgia syndrome (FMS), is a chronic condition that causes widespread pain throughout the body (World Health Organization. Regional Office for the Eastern Mediterranean, 2013). More specifically, people with fibromyalgia have a higher sensitivity to pain, that is, a lower pain threshold. In addition, they can also have several associated symptoms, the most common being extreme tiredness (fatigue), muscle stiffness, sleep disorders and problems in the mental process (memory and attention). All of this makes these patients very susceptible to depression, which is why it is common for treatment to also involve psychologists and psychiatrists.
Galvez-Sánchez and Reyes del Paso (2020) explained about its non-inflammatory, multisystemic characteristic and with a multitude of concomitant syndromes, compatible with the disease. This fact should make us reflect on the limited capacity of thermography in this condition. Without inflammation, the main thermal sign detectable in humans, this disease becomes invisible in thermography, as can be seen in figure 1. This explains that the thermographic analysis of a fibromyalgia patient results in an almost perfect symmetry, despite the fact that there are many regions with pain (the symptoms are shown by rounding the regions with pain in purple).
Figure 1. The regions of pain that the patient provides us and the regions with significant thermal asymmetry are appreciated. It is important to highlight the lack of correlation between symptoms and thermal findings in this type of pathology.
Fibromyalgia affects between 2 and 4% of the European and North American population, with an estimated prevalence of 2.4% for Spain, where 13,000 million euros are allocated to its treatment (Cabo-Meseguer et al., 2017). Despite the association between some factors and the prevalence of fibromyalgia (genetics, negative life events and physical trauma) it is still considered a disease of unknown etiology (Bohn et al., 2013; Häuser et al., 2011). It is definitely a syndrome with very complex diagnosis and, in many cases, with little diagnostic certainty.
One of the greatest experts in thermography (Ammer, 2008), already said in 2008 that thermography is a technology that has not demonstrated sufficient clinical precision for the diagnosis of fibromyalgia. Recent studies (Sempere-Rubio et al., 2021) confirm it, showing that patients with this pathology obtain thermal results that are similar to those obtained by healthy people. When the 86 women with fibromyalgia were compared to 92 healthy women, the results showed no significant differences in skin temperature between the groups in the neck, upper back, chest, and elbows (p> 0.05 ). The lower back and knee areas showed significant differences between the groups (p <0.05), although these differences did not achieve a minimum of clinically detectable change. Therefore, we can assert that women with fibromyalgia did not present a clinically significant reduction or difference in skin temperature at rest compared to a group of healthy women. It has been seen that in the approach to other complex diseases related to pain, such as complex regional pain syndrome, there is evidence of the power of thermography to improve diagnostic precision (Pérez-Concha et al., 2020).
The fibromyalgia diagnostic process is often very long and tedious, and can last up to years. During this time, one of the main tasks is to rule out other pathologies with similar symptoms. The most important problem in the diagnosis is the lack of objective markers or reliable and valid clinical measures (Moyano et al., 2015). Therefore, until the etiology and pathophysiology are better understood, the diagnosis should be based on clinical evaluation and patient reports.
Therefore, the main objective of thermography when fibromyalgia is suspected is to rule out rheumatic diseases, common concomitants, such as osteoarthritis, lupus, rheumatoid arthritis or ankylosing spondylitis. In figure 2, we can see examples of patients' thermograms with knee osteoarthritis and rheumatoid arthritis in the hands and wrists.
Figure 2 . Thermogram and avatar of asymmetries in the hands of a patient with rheumatoid arthritis (left) and another patient with knee osteoarthritis (right).
In observational studies, it has been verified that the 2010 ACR criteria have a sensitivity of 96.6% and a specificity of 91.8% to discriminate fibromyalgia from rheumatoid arthritis and osteoarthritis (Wolfe et al., 2010). In studies with samples from Spain, a sensitivity of 85.6% and a specificity of 73.2% have been estimated to discriminate fibromyalgia from these pathologies (Casanueva et al., 2016) , being the main aspects to be evaluated in the classification of the patient with FMS, the psychopathological profile and the coexistence of other processes (Belenguer et al., 2009) .
Despite the apparently favorable results, in subsequent studies, the same authors admit that this criterion is unable to discriminate with many other pathologies (Wolfe et al., 2016), which opens possibilities for other technologies, such as thermography. On the other hand, it seems clear that fibromyalgia patients have a lower pain threshold when stressed with cold than healthy people. Also, recovery of the cooled region takes longer (Brusselmans et al., 2015). This is further proof of the power of dynamic thermography in the approach of fibromyalgia.
Recently, Casas-Barragan et al. (2021) have carried out a study with 80 patients with diagnosed fibromyalgia and 80 healthy patients, to evaluate the differences between the painful pressure points in both groups of patients and the relationship with the thermographic evaluation of the hand in its hypothenar eminence. This region was chosen because of its relationship to altered neurovascularization in fibromyalgia patients. The results indicate that there is a difference between the pressure points in the hip region and the temperature of the hypothenar eminence in patients with fibromyalgia, which could indicate that temperature control may help to establish evaluation criteria for fibromyalgia.
Despite everything we know about fibromyalgia, in a real clinical context, it seems that the vast majority of health professionals continue to use digital palpation to establish a diagnosis (Galvez-Sánchez & Reyes del Paso, 2020). Therefore, it is our obligation to disclose the use of thermography in order to improve professionalism in the management of this complex pathology. Specifically, in the arduous task of ruling out the immense number of concomitant pathologies that appear frequently and make the choice of the correct treatment difficult.
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Belenguer, R., Ramos-Casals, M., Siso, A., & Rivera, J. (2009). Clasificación de la fibromialgia. Revisión sistemática de la literatura. Reumatología Clínica, 5(2), 55-62. https://doi.org/10.1016/j.reuma.2008.07.001
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Brusselmans, G., Nogueira, H., De Schamphelaere, E., Devulder, J., & Crombez, G. (2015). Skin Temperature during Cold Pressor Test in Fibromyalgia: An Evaluation of the Autonomic Nervous System. Acta Anaesthesiologica Belgica, 66(1), 19-27.
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Casanueva, B., García-Fructuoso, F., Belenguer, R., Alegre, C., Moreno-Muelas, J. V., Hernández, J. L., Pina, T., & González-Gay, M. Á. (2016). The Spanish version of the 2010 American College of Rheumatology Preliminary Diagnostic Criteria for fibromyalgia: Reliability and validity assessment. Clinical and Experimental Rheumatology, 34(2 Suppl 96), S55-58.
Casas-Barragán A, Molina F, Tapia-Haro RM, García-Ríos MC, Correa-Rodríguez M, Aguilar-Ferrándiz ME. Association of core body temperature and peripheral blood flow of the hands with pain intensity, pressure pain hypersensitivity, central sensitization, and fibromyalgia symptoms. Ther Adv Chronic Dis. 2021;12:2040622321997253. Published 2021 Mar 5. doi:10.1177/2040622321997253
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Pérez-Concha, T., Tijero, B., Acera, M., Fernández, T., Gabilondo, I., & Gómez-Esteban, J. C. (2020). Usefulness of thermography in the diagnosis and classification of complex regional pain syndrome. Neurología, S0213485320303376. https://doi.org/10.1016/j.nrl.2020.10.011
Sempere-Rubio, N., Aguilar-Rodríguez, M., Inglés, M., Izquierdo-Alventosa, R., & Serra-Añó, P. (2021). Thermal imaging ruled out as a supplementary assessment in patients with fibromyalgia: A cross-sectional study. PLOS ONE, 16(6), e0253281. https://doi.org/10.1371/journal.pone.0253281
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ThermoHuman has had the support of the Funds of the European Union and the Community of Madrid through the Operational Programme on Youth Employment. Likewise, ThermoHuman within the framework of the Export Initiation Program of ICEX NEXT, had the support of ICEX and the co-financing of the European Regional Development Fund (ERDF).
Thermohuman has received funding from the Centre for the Development of Industrial Technology (CDTI), in participation with the European Regional Development Fund (ERDF), for the R+D activities involved in creating a new tool, based on thermography, for the prediction and prevention of rheumatoid arthritis. See project detail.
