Chronic widespread pain (CWP) is the obvious symptom of fibromyalgia (FM), but may also occur as a symptom of other diseases.
There are many factors that contribute to uncertainties surrounding the diagnosis of FM, including reliance on patient report of subjective symptoms,absence of a universally accepted diagnostic gold standard.
Various diagnostic and classification criteria for FM have been proposed in the last 2 decades, with considerable debate regarding the concept of FM as a unique diagnosis, or as a condition that may associate with some other illness.
Although the most likely reason for a complaint of CWP is FM,this pain complaint can be because of other disease, prompting consideration of a differential diagnosis. The key-point here is the differential diagnosis.
You will find in the article clues for how to recognize if the cause of CWP is fibromyalgia or not.
https://docs.wixstatic.com/ugd/a87948_0c50a7378f1e4f41bd9cd5ae015aa490.pdf