Diagnosis
There is no single pathological feature, laboratory finding, or biomarker that can diagnose fibromyalgia and there is debate over what should be considered diagnostic criteria and whether an objective diagnosis is possible. In most cases, people with fibromyalgia symptoms may have laboratory test results that appear normal and many of their symptoms may mimic those of other rheumatic conditions such as arthritis or osteoporosis. The specific diagnostic criteria for fibromyalgia have evolved over time. American College of Rheumatology 1990
The first widely accepted set of classification criteria for research purposes was elaborated in 1990 by the Multicenter Criteria Committee of the American College of Rheumatology. These criteria, which are known informally as "the ACR 1990", defined fibromyalgia according to the presence of the following criteria:

A history of widespread pain lasting more than three months – affecting all four quadrants of the body, i.e., both sides, and above and below the waist. Tender points – there are 18 designated possible tender points (although a person with the disorder may feel pain in other areas as well).The ACR criteria for the classification of patients were originally established as inclusion criteria for research purposes and were not intended for clinical diagnosis but have later become the de facto diagnostic criteria in the clinical setting. A controversial study was done by a legal team looking to prove their clients disability based primarily on tender points and their widespread presence in non-litigious communities prompted the lead author of the ACR criteria to question now the useful validity of tender points in diagnosis.
Hyperbaric oxygen therapy
Hyperbaric oxygen therapy (HBOT) has shown beneficial effects in treating chronic pain. However, treating fibromyalgia with hyperbaric oxygen therapy is still controversial, in light of the scarcity of large-scale clinical trials. In addition, hyperbaric oxygen therapy raises safety concerns due to the oxidative damage that may follow it. Prognosis
Although in itself fibromyalgia is neither degenerative nor fatal, the chronic pain of fibromyalgia is pervasive and persistent. Most people with fibromyalgia report that their symptoms do not improve over time. However, most patients learn to adapt to the symptoms over time. The German guidelines for patients explain that:

The symptoms of fibromyalgia are persistent in nearly all patients. Total relief of symptoms is seldom achieved. The symptoms do not lead to disablement and do not shorten life expectancy.An 11-year follow-up study on 1,555 patients found that most remained with high levels of self-reported symptoms and distress. However, there was a great deal of patient heterogeneity accounting for almost half of the variance. At the final observation, 10% of the patients showed substantial improvement with minimal symptoms. An additional 15% had moderate improvement. This state, though, may be transient, given the fluctuations in symptom severity.A study of 97 adolescents diagnosed with fibromyalgia followed them for eight years. After eight years, the majority of youth still experienced pain and disability in physical, social, and psychological areas. At the last follow-up, all participants reported experiencing one or more fibromyalgia symptoms such pain, fatigue, and/or sleep problems, with 58% matching the complete ACR 2010 criteria for fibromyalgia.