Description

The International Association for the Study of Pain (IASP) defined chronic pain as pain that persists or recurs for more than three months. In the case of conditions such as FM, it can be conceived as a disease in its own, right de- scribed as "chronic primary pain", and the existence of such persisting pain, despite adequate treatment and in the absence of any sign of inflammation, has led researchers to look for evidence of central sensitization.

Misuse and misreporting of chronic pain assessment run deep, both in research and the clinical setting. Chronic pain diagnosis lacks specific tools to objectively define pathology, unlike other diseases (e.g., oncology or infectiol- ogy), where biomarkers play a well-known role. The objectivity of pain severity is still described only in terms of pain threshold and patients have to rate their pain considering a numeric rating scale (NRS) of 0 to 10, where zero is a no pain condition and a 10 means the pain is as bad as it could be, even if it involves many other factors, such as anthropological, spiritual, genetic, social, and psychological personal experience.

Currently, there is no internationally accepted classification of pain severity for FM and the physician is tasked with careful evaluation in order to determine the most effective treatment. It is common practice to consider a '30% reduction' in pain reported in verbal numerical rating scores (VNRS) as adequate pain response to treatment. This is problematic for several reasons. While there have been arguments for and against the linearity of a properly ad- ministered VAS there is no adequate evidence that a VNRS can be treated as linear, nor that any given score repre- sents the same thing from one individual to another or indeed from one day to another even for any given individ- ual. The use of a mean to summarize VNRS data is therefore likely to be inappropriate, as would be the application of parametric statistics to those data, although this is perhaps more controversial if the samples are very large. For the same reason, it is not appropriate to quantify a percent reduction in pain from such a study. Given the multidi- mensional and very individual nature of the pain experience, the concept of quantifying any alteration in pain as a percentage does not seem appropriate.

The American College of Rheumatology (ACR) criteria for FM diagnosis have changed over time, maintaining ad- vantages and limitations and clinicians rely only on clinical examination and questionnaire administration to make a diagnosis. Neither specific diagnostic laboratory tests nor biomarkers are available to confirm FM diagnosis, espe- cially in its specificity of chronic widespread pain (CWP). Little is known about the role of opioid receptors on circu- lating cells during the development of a chronic pain disease. In recent years, attention has been focused on the close association between peripheral nerve and opioid-containing immune cells. Both immune cells and neurons share common ligands and receptors, and this ligand-receptor communication influences and activates cellular pathways in both systems. The complex communication between endogenous antinociceptive systems, pathology and peripheral opioid receptors has encouraged a hypothesis that lymphocyte opioid Mu receptor (MOR) expression could serve as a biomarker for FM diagnosis and pain assessment. In a recent study, the percentage of Mu-positive B cells was investigated as a biological marker for an objective diagnosis of chronic pain suffering patients, also con- tributing to the legitimacy of FM as a truly painful disease. . In the study by Raffaeli et al, it was certi- fied that FM pain perception is an objective widespread chronic pain status where pain is the primary symptom and FM pathogenesis derives from a characteristic morphological modulation of the endogenous antinociceptive path- way. It was suggested that a lower expression of Mu+ B cells in FM patients seemed to be linked to a reduced thresh- old level of pain response and that a low availability of opioid receptors in FM patients could show altered endoge- nous opioid analgesic activity.

A multimodel assessment model of pain incorporates pain experience, pain expression, and pain measures. The aim of our study is to evaluate the effectiveness of electroacupuncture on the "whole" pain experience and quality of life in FM patients with the use of multiple tools; in addition to a patient's self-reported value on a numerical scale for the assessment of pain will be used:

1. measurement of percentage of Mu + B-lymphocytes in a blood sample (biological marker)
2. assessment of pressure pain thresholds with the use of an algometer
3. PSD scale for monitoring the severity of fibromyalgia symptoms
4. quality of life questionnaire in patients with fibromyalgia
5. Detection of depression with a questionnaire (Patient health questionnaire, PHQ-9) It is the first time that mu-receptor (MOR) expression in B lymphocytes will be used as biomarker of pain re- sponse to treatment in patients with fibromyalgia undergoing electro-acupuncture treatment.