title: Test-retest variability of multifocal electroretinography in normal volunteers and short-term variability in hydroxychloroquine users.
abstract: OBJECTIVE
  To determine measurement variability of N1P1 amplitudes and the R1/R2 ratio in normal subjects and hydroxychloroquine users without retinopathy.
  
  
  METHODS
  Retrospective, observational study.
  
  
  METHODS
  Normal subjects (n=21) and 44 patients taking hydroxychloroquine (n=44) without retinopathy.
  
  
  METHODS
  Multifocal electroretinography (mfERG) was performed twice in one session in the 21 normal subjects and twice within 1 year in the hydroxychloroquine users, during which time no clinical change in macular status occurred.
  
  
  METHODS
  N1P1 amplitudes of rings R1-R5, the R1/R2 ratio, and coefficients of repeatability (COR) for these measurements.
  
  
  RESULTS
  Values for N1P1 amplitudes in hydroxychloroquine users were reduced compared with normal subjects by the known effect of age, but R1/R2 was not affected by age. The COR for R1-R5 ranged from 43% to 52% for normal subjects and from 43% to 59% for hydroxychloroquine users; for R1/R2 the COR was 29% in normal subjects and 45% in hydroxychloroquine users.
  
  
  CONCLUSIONS
  mfERG measurements show high test-retest variability, limiting the ability of a single mfERG test to influence a decision to stop hydroxychloroquine; corroborative evidence with a different ancillary test is recommended in a suspicious case.
authors.affiliation: Charlotte Eye, Ear, Nose and Throat Associates, USA.
authors.forename: David J
authors.initials: DJ
authors.lastname: Browning
authors.affiliation: University of North Carolina - Charlotte, Charlotte, NC, USA.
authors.forename: Chong
authors.initials: C
authors.lastname: Lee
keywords: hydroxychloroquine; multifocal electroretinography; test-retest variability