title: Application of futility analysis to refine jitter recordings in myasthenia gravis.
abstract: BACKGROUND
  The current practice of single-fiber electromyography (SFEMG) requires that 20 fiber pairs with normal jitter be collected to exclude myasthenia gravis (MG). We applied principles of futility analysis from clinical trials in an attempt to reduce that requirement.
  
  
  METHODS
  We utilized conditional power futility analysis to assess the probability of an abnormal 20-pair SFEMG based on ongoing analysis of jitter as each pair is collected. Rules for early test termination in the presence of 0, 1, or 2 abnormal pairs were identified. These rules were then applied to previously collected SFEMG data.
  
  
  RESULTS
  SFEMG could be stopped at just 12 pairs if all are normal and at 17 pairs if 1 is abnormal. The rules successfully determined when SFEMG could be stopped in 104 of 106 (98%) studies originally reported to be normal.
  
  
  CONCLUSIONS
  If the first 12 SFEMG pairs have normal jitter, the study can be terminated and interpreted as normal.
authors.affiliation: Department of Neurology, Harvard Medical School, Beth Israel Deaconess Medical Center, TCC-8, 330 Brookline Avenue, Boston, Massachusetts 02215, USA. pnarayan@bidmc.harvard.edu
authors.forename: Pushpa
authors.initials: P
authors.lastname: Narayanaswami
authors.forename: Norberto
authors.initials: N
authors.lastname: Pantoja-Galicia
authors.forename: Rebecca A
authors.initials: RA
authors.lastname: Betensky
authors.forename: Seward B
authors.initials: SB
authors.lastname: Rutkove
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D002648:Child; D003627:Data Interpretation, Statistical; D004576:Electromyography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018485:Muscle Fibers, Skeletal / Q000502:physiology; D009157:Myasthenia Gravis / Q000503:physiopathology*; D009412:Nerve Fibers / Q000502:physiology; D009460:Neurologic Examination / Q000379:methods* / Q000706:statistics & numerical data*; D011336:Probability; D015203:Reproducibility of Results; D055815:Young Adult