Why is the diagnosis of fibromyalgia often missed?

Missed by whom?: I'm uncertain what you mean by mised. All medical diagnoses have to clarify themselves before they can be identified. As symptoms and signs change clarity helps in the diagnosis. A medical diagnosis depends both on the patient, and their description of their problems and the findings discovered by the physician. Missing applies to both partners in this setting.

Fibromyalgia: To this day many physicians do not believe in fibromyalgia as a diagnosis. Many physicians do not pick up fibro because its so vague in how it presents.

Poor definition: Fibromyalgia (fm) diagnosis difficult because lab tests & physical examination criteria do not exist. Standard of proof currently a short symptom questionaire. Unfortunate because most sufferers have demonstrable physical examination findings of sacroiliac joint subluxation; exam described in occupational disabilities guidelines (odg). See discussions on my pain board at quora.Com (free).