title: Laboratory validation of an in-home method for assessing circadian phase using dim light melatonin onset (DLMO).
abstract: OBJECTIVE
  To determine whether an accurate circadian phase assessment could be obtained from saliva samples collected by patients in their home.
  
  
  METHODS
  Twenty-four individuals with a complaint of sleep initiation or sleep maintenance difficulty were studied for two evenings. Each participant received instructions for collecting eight hourly saliva samples in dim light at home. On the following evening they spent 9h in a laboratory room with controlled dim (<20 lux) light where hourly saliva samples were collected. Circadian phase of dim light melatonin onset (DLMO) was determined using both an absolute threshold (3 pg ml(-1)) and a relative threshold (two standard deviations above the mean of three baseline values).
  
  
  RESULTS
  Neither threshold method worked well for one participant who was a "low-secretor". In four cases the participants' in-lab melatonin levels rose much earlier or were much higher than their at-home levels, and one participant appeared to take the at home samples out of order. Overall, the at-home and in-lab DLMO values were significantly correlated using both methods, and differed on average by 37 (± 19)min using the absolute threshold and by 54 (± 36)min using the relative threshold.
  
  
  CONCLUSIONS
  The at-home assessment procedure was able to determine an accurate DLMO using an absolute threshold in 62.5% of the participants. Thus, an at-home procedure for assessing circadian phase could be practical for evaluating patients for circadian rhythm sleep disorders.
authors.affiliation: Division of Sleep Medicine, Department of Medicine, Brigham and Women's Hospital, Boston, MA 02115, USA.
authors.forename: Rebecca E
authors.initials: RE
authors.lastname: Pullman
authors.forename: Stephanie E
authors.initials: SE
authors.lastname: Roepke
authors.forename: Jeanne F
authors.initials: JF
authors.lastname: Duffy
mesh_terms: D000328:Adult; D000368:Aged; D002624:Chemistry, Clinical / Q000379:methods / Q000592:standards*; D002940:Circadian Rhythm / Q000502:physiology*; D005260:Female; D006801:Humans; D008029:Lighting; D008297:Male; D008550:Melatonin / Q000378:metabolism*; D008875:Middle Aged; D010358:Patient Participation; D015203:Reproducibility of Results; D012463:Saliva / Q000378:metabolism*; D007319:Sleep Initiation and Maintenance Disorders / Q000175:diagnosis* / Q000378:metabolism*; D013048:Specimen Handling / Q000592:standards; D055815:Young Adult
chemical_list: D008550:Melatonin