title: Quantitative nailfold video capillaroscopy in patients with idiopathic inflammatory myopathy.
abstract: OBJECTIVE
  To quantify nailfold capillary density and dimensions in patients with idiopathic inflammatory myopathy (IIM) and compare them with those in healthy controls; to look for associations with microvascular disease in IIM; and to determine whether nailfold capillary density and dimensions change over time.
  
  
  METHODS
  Nailfold video microscopy (x300 magnification) was performed on 24 patients with IIM and 35 healthy controls. Capillary density and dimensions (total width and apical width) were quantified. Patients were clinically assessed and disease activity recorded using the Myositis Disease Activity Assessment Tool. Disease severity and physical function were assessed using the myositis damage index and Stanford HAQ, respectively. Findings were analysed using linear and logistic regression, adjusted for age and sex. In a subgroup of 16 patients with IIM and 27 controls, the process was repeated 6-12 months later and the results were analysed using Student's t-test.
  
  
  RESULTS
  Capillary density was lower and dimensions were higher in patients with IIM compared with healthy controls (P < 0.001 for all). Anti-Jo-1 antibody was associated with reduced capillary density. In the longitudinal cohort, the mean change in capillary density was -1.4 in patients vs -0.4 in controls (P = 0.07). Mean change in capillary dimensions did not differ between patients and controls, but some patients demonstrated pronounced changes in capillary morphology over time.
  
  
  CONCLUSIONS
  Reduced capillary density and increased dimensions in patients with IIM can be quantified using nailfold capillaroscopy, suggesting that nailfold capillaroscopy may be useful as an outcome measure of microvascular disease in studies of IIM.
authors.affiliation: ARC Epidemiology Unit, University of Manchester, Stopford Building, Oxford Road, Manchester M13 9PT, UK. louise.mercer@manchester.ac.uk
authors.forename: Louise K
authors.initials: LK
authors.lastname: Mercer
authors.forename: Tonia L
authors.initials: TL
authors.lastname: Moore
authors.forename: Hector
authors.initials: H
authors.lastname: Chinoy
authors.forename: Andrea K
authors.initials: AK
authors.lastname: Murray
authors.forename: Andy
authors.initials: A
authors.lastname: Vail
authors.forename: Robert G
authors.initials: RG
authors.lastname: Cooper
authors.forename: Ariane L
authors.initials: AL
authors.lastname: Herrick
mesh_terms: D000328:Adult; D000368:Aged; D002196:Capillaries; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D008297:Male; D020678:Microscopic Angioscopy / Q000379:methods*; D018715:Microscopy, Video; D008875:Middle Aged; D009220:Myositis / Q000503:physiopathology*; D009262:Nails / Q000098:blood supply*; D012044:Regression Analysis; D015203:Reproducibility of Results; D012720:Severity of Illness Index