Fdk 20

A cross-sectional research study was performed between March and October 2012, and approved by the Research Ethics Committee of the Hospital de Clínicas of the Federal University of Paraná (HC/UFPR). The study analyzed women in ages between 18 to 60 years, selected at the Rheumatology Outpatient Clinic at the HC/UFPR, who had been diagnosed with FM according to criteria set forth by the American College of Rheumatology (ACR) in 1990 [18] . The reason for including only women in the study was the low prevalence of fibromyalgia among men. The control group consisted of women with the same age span who did not have FM and other associated clinical conditions.
Patients with fibromyalgia and depression or anxiety were only included if their treatment had remained unchanged for 3 months. The exclusion criteria were: use of calcium and magnesium supplements, medication change over the previous 4 weeks, use of corticosteroids or anticytokine agents, pregnancy, lactation, and a diagnosis of diabetes, decompensated endocrine diseases, infectious diseases (over the previous 4 weeks), demyelinating neurological diseases, peripheral neuropathies, inflammatory articular diseases, systemic autoimmune diseases, severe cardiovascular diseases, malignancy (over the previous year), and severe psychiatric diseases (substance abuse, schizophrenia, psychosis). Nonsteroidal anti-inflammatory agents were suspended 48 h before collection of blood samples, and all other medications were required to remain unchanged for at least 30 days.
After having executed an Informed Consent Agreement, all women underwent anthropometric assessment, physical exam of pain perception threshold and tender point (TP) count, blood sample collection, filling out of FM impact questionnaire, (FIQ), of Patient Health Questionnaire-9 (PHQ-9), and 3-day dietary record (DR).
Anthropometric assessment was performed by means of body mass index (BMI) consisting of the relation between body weight in kilograms and body height squared in meters: BMI = weight/height(m) 2 [19] .
The pain threshold was evaluated at the trapezius muscle, using a Fischer algometer (model FDK 20, Wagner Instruments, Greenwich, CT, USA). Each TP was manually palpated with a strength of 4 kgf/cm 2 and the response was recorded as positive (with pain) or negative (without pain). In order to measure the pain threshold in the TP located in the right trapezius, the algometer was placed against the skin of the participant and pressed with a strength of 1 kgf/s until pain onset. Then, the pressure (in kgf/cm 2 ) was recorded and defined as the pain threshold.
Blood samples for measuring serum magnesium (Mg) and calcium (Ca) were drawn in the morning after a 10-12-h fasting. Samples were then placed in ice and centrifuged at 4 °C. Serum was stored at -80 °C. for later analysis at the UFPR Clinical Analysis Laboratory. For the determination of Mg and Ca levels, the Abbott C9000 and/or Ci8200 devices were used. According to the laboratory, reference range values for serum magnesium are 1.6-2.6 mg/dL and for serum calcium are 8.9-10 mg/dL.
The FIQ was employed to assess the impact of FM in quality of life. This questionnaire covers matters related to functional capacity, professional situation, psychological disorders and physical symptoms. It features a score ranging from 0 to 100the higher the score, the greater the impact of FM in quality of lifeconsequently, the lower the overall health [20] (link).
PHQ-9 is a tool with 9 items used to identify individuals in risk of depression. Its score ranges from 0 to 27, with possible answers variating between 0 (not at all) and 3 (nearly every day). The higher the score, the higher the severity [21] .
In order to fill out the Dietary Record, subjects were instructed to take notes on a form including the sort of food and drink they have had and their quantities, three times, in alternate days including 1 day on weekend [22] . Later, all these information was inputed in Avanutri® software and the average dietary intake was calculated. According to the DRIs (Dietary Reference Intakes), the EAR (Estimated Average Requirement) for Mg is 255 mg/d for women aged between 19 and 30 years, and 265 mg/d for women older than 31 years. For Ca, the EAR is 800 mg/d for women aged between 19 and 50 years and 1000 mg/d for women older than 51 years [23] .