title: The sawtooth sign is predictive of obstructive sleep apnea.
abstract: BACKGROUND
  The sawtooth sign in spirometry is associated with redundant upper airway tissue and snoring, but its predictive value for identifying obstructive sleep apnea (OSA) is disputed. We retrospectively assessed the predictive value of the spirometric sawtooth sign in terms of the odds ratio (OR) of association with a diagnosis of OSA compared to those without the sign.
  
  
  METHODS
  Consecutive spirometry reports showing a sawtooth sign were identified from our laboratory. We identified 50 subjects with sawtooth sign and 100 control subjects without sawtooth sign, matched for age, BMI, and gender. The electronic medical record of each patient was queried for a diagnosis of OSA based on physician-reported diagnoses.
  
  
  RESULTS
  Of the 50 subjects with sawtooth sign, 22 were found to have a current diagnosis of OSA (44%). Twenty-seven of the 100 controls (27%) also had OSA. From logistic regression analysis, sawtooth sign was associated with an increased likelihood of OSA (OR = 2.12, 95% C.I. 1.04 to 4.35). Similar results were obtained after adjustment for age, gender, pack years, and BMI (OR = 2.61, 95% C.I. 1.13 to 6.21).
  
  
  CONCLUSIONS
  Patients with the sawtooth sign have greater odds of having a diagnosis of OSA compared with those without the sign. If prospectively evaluated, as a result of improved identification, we hypothesize that the sawtooth sign may show an even stronger association with OSA. This relatively common finding, which adds no cost to routine spirometry, may serve as an indicator for OSA workup for some individuals not already identified as having OSA.
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Mayo Clinic, 200 First St SW, Rochester, MN, 55905, USA. bourne.michael@mayo.edu.
authors.forename: Michael H
authors.initials: MH
authors.lastname: Bourne
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Mayo Clinic, 200 First St SW, Rochester, MN, 55905, USA.
authors.forename: Paul D
authors.initials: PD
authors.lastname: Scanlon
authors.affiliation: Biomedical Statistics and Informatics, Mayo Clinic, Rochester, MN, USA.
authors.forename: Darrell R
authors.initials: DR
authors.lastname: Schroeder
authors.affiliation: Center for Sleep Medicine, Mayo Clinic, Rochester, MN, USA.
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Olson
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D015992:Body Mass Index; D005260:Female; D006801:Humans; D016013:Likelihood Functions; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D012737:Sex Factors; D020181:Sleep Apnea, Obstructive / Q000175:diagnosis*; D013147:Spirometry
keywords: Obstructive sleep apnea; Sawtooth sign; Smoking; Spirometry