[Frequent urination--an important diagnostic marker in fibromyalgia].

Background: Detailed studies of a family with a strong clustering of fibromyalgia revealed that the affected members had eight or more urinations per day and at least one per night. As this feature was not known to be an important symptom in this ailment, we carried out a questionnaire-based study.

Material And Methods: Questionnaires were mailed to a random group of 285 subjects drawn from the member list of the Norwegian Fibromyalgia Association, and to 160 healthy females, free of urinary tract pains. Response rates were 70% and 74%.

Results: The fibromyalgia group reported 8 or more daily and 1 permanent nocturnal urinations; the corresponding figures for healthy females were 6 and 0.2. This corresponds to a sensitivity and specificity for fibromyalgia of 78 and 91% for daytime urinations, and to 89% and 92% for one or more permanent nocturia.

Interpretation: The study indicates that an abnormally high frequency of urinations is a characteristic feature in fibromyalgia and a useful diagnostic variable. It is also objectively verifiable by urodynamic investigation. The pattern is that of urge, sometimes with incontinence.