title: The value of routine creatine kinase and thyroid stimulating hormone testing in patients with suspected fibromyalgia: a cross-sectional study.
abstract: The aim was to examine the prevalence of abnormal creatine kinase (CK) and thyroid stimulating hormone (TSH) values and previously unknown myopathy or thyroid disease in patients with suspected FM syndrome (FMS).
  
  
  
  All adult patients with suspected FMS referred to the study hospital between November 2011 and April 2014 could participate. Patients with a history of myopathy or a previous diagnosis of thyroid disorder were excluded. Outcome measures were the percentages of abnormal CK and TSH values and the final diagnosis in those patients.
  
  
  
  Three hundred and seventy-three patients were included in this study (94% female, mean age 42 years). Of these patients, 7.5% (95% CI: 5.2, 10.6%) had an abnormal CK according to the local reference values. Applying the European Federation of the Neurological Societies guideline, this changed to 0.5% (95% CI: 0.2, 1.9%). In none of these patients was hyperCKaemia-related myopathy diagnosed, and the final diagnosis was FMS in 89% of the patients. Of the total number of patients, 3.5% (95% CI: 2.1, 5.9%) had an elevated TSH and 1.4% (95 CI: 0.6, 3.1%) a lowered TSH, with one patient having a somewhat lowered free thyroid hormone level. The final diagnosis was FMS in all these patients.
  
  
  
  Abnormal CK and TSH values are rare in patients with suspected FMS and do not result in an alternative diagnosis. Therefore, it seems that routine testing of CK and TSH levels in patients with suspected FMS referred to secondary care does not contribute to the diagnostic process.
authors.affiliation: Department of Rheumatology, Sint Maartenskliniek n.lesuis@maartenskliniek.nl.
authors.forename: Nienke
authors.initials: N
authors.lastname: Lesuis
authors.affiliation: Department of Neurology, Canisius Wilhelmina Ziekenhuis and.
authors.forename: Judith
authors.initials: J
authors.lastname: van Vliet
authors.affiliation: Department of Rheumatology, Sint Maartenskliniek.
authors.forename: Nadine
authors.initials: N
authors.lastname: Boers
authors.affiliation: Department of Rheumatology, Sint Maartenskliniek.
authors.forename: Nathan
authors.initials: N
authors.lastname: den Broeder
authors.affiliation: Department of Rheumatology, Sint Maartenskliniek.
authors.forename: Hans
authors.initials: H
authors.lastname: Cats
authors.affiliation: Radboud Institute for Health Sciences, IQ healthcare, Radboud University Medical Centre, Nijmegen, The Netherlands.
authors.forename: Marlies E J L
authors.initials: ME
authors.lastname: Hulscher
authors.affiliation: Department of Neurology, Canisius Wilhelmina Ziekenhuis and.
authors.forename: Aad
authors.initials: A
authors.lastname: Verrips
authors.affiliation: Department of Rheumatology, Sint Maartenskliniek.
authors.forename: Alfons A
authors.initials: AA
authors.lastname: den Broeder
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood; D003402:Creatine Kinase / Q000097:blood*; D003430:Cross-Sectional Studies; D005260:Female; D005356:Fibromyalgia / Q000097:blood / Q000175:diagnosis*; D006801:Humans; D008297:Male; D011237:Predictive Value of Tests; D012016:Reference Values; D013972:Thyrotropin / Q000097:blood*
chemical_list: D015415:Biomarkers; D013972:Thyrotropin; D003402:Creatine Kinase
keywords: creatine kinase; diagnostic value; fibromyalgia; thyroid stimulating hormone