title: E-norms: a method to extrapolate reference values from a laboratory population.
abstract: OBJECTIVE
  Collecting reference values in subpopulations such as infants and children can pose a daunting challenge to gather through epidemiologic studies. The authors propose to evaluate a method the authors refer to as extrapolated norms (e-norms) to derive Stimulated Single Fiber EMG jitter reference values from the laboratory data of pediatric and adult cohorts. Single Fiber EMG studies are considered the gold standard test for evaluation of neuromuscular transmission disorders.
  
  
  METHODS
  Data that lie in the plateau part of an inverted S curve derived from sorted jitter data were used to calculate descriptive statistics for pediatric and adult e-norms jitter.
  
  
  RESULTS
  The e-norms derived jitter was 22 ± 2.83 μs for our pediatric and 21 ± 2.79 μs for our adult cohort. Our adult e-norms values compared favorably with the 22 ± 1.99 μs published jitter range derived from a healthy adult cohort.
  
  
  CONCLUSIONS
  The e-norms method the authors describe seems to be useful in recovering reference ranges when such values are difficult to obtain, such as in a pediatric subpopulation.
authors.affiliation: *Department of Neurology, Boston University School of Medicine, Boston, Massachusetts, U.S.A.; †Department of Clinical Neurophysiology, Great Ormond Street Hospital for children NHS Foundation Trust, London, United Kingdom; ‡Department of Neurophysiology, Queen's Hospital, Barking, Havering and Redbridge University Hospitals NHS Trust, London, United Kingdom; and §Department of Public Health and Community Medicine, Tufts University School of Medicine, Boston, Massachusetts, U.S.A.
authors.forename: Joe F
authors.initials: JF
authors.lastname: Jabre
authors.forename: Matthew C
authors.initials: MC
authors.lastname: Pitt
authors.forename: Jacquie
authors.initials: J
authors.lastname: Deeb
authors.forename: Kenneth K H
authors.initials: KK
authors.lastname: Chui
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D004576:Electromyography; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008875:Middle Aged; D012016:Reference Values; D055815:Young Adult