title: The presence of pepsin in the lung and its relationship to pathologic gastro-esophageal reflux.
abstract: BACKGROUND
  Pepsin has been proposed as a biomarker of reflux-related lung disease. The goal of this study was to determine (i) if there is a higher reflux burden as measured by pH-MII in patients that are pepsin positive in the lung, and (ii) the sensitivity of pepsin in predicting pathologic reflux by pH, MII, and EGD.
  
  
  METHODS
  We recruited children between the ages of 1-21 with chronic cough or asthma undergoing bronchoscopy, esophagogastroduodenoscopy (EGD), and multichannel intraluminal impedance (pH-MII) probe placement. The reflux profiles were compared between those patients who were pepsin positive and negative; proportions were compared using Chi-squared analyses and means were compared using t-testing.
  
  
  RESULTS
  Only the mean number of non-acid reflux events was associated with pepsin positivity (0.04). The sensitivity and specificity of pepsin in predicting pathologic reflux by pH-MII or EGD was 57% and 65%, respectively. The positive predictive value of pepsin in predicting pathologic reflux by pH, MII or EGD was 50% (11/22), and the negative predictive value was 71% (20/28). There was a significantly higher mean LLMI in patients who were pepsin positive compared with pepsin negative patients (81 ± 54 vs 47 ± 26, P = 0.001).
  
  
  CONCLUSIONS
  Lung pepsin cannot predict pathologic reflux in the esophagus, but its correlation with lung inflammation suggests that pepsin may be an important biomarker for reflux-related lung disease.
authors.affiliation: Center for Motility and Functional Gastrointestinal Disorders, Children's Hospital Boston, Boston, MA 02115, USA. rachel.rosen@childrens.harvard.edu
authors.forename: R
authors.initials: R
authors.lastname: Rosen
authors.forename: N
authors.initials: N
authors.lastname: Johnston
authors.forename: K
authors.initials: K
authors.lastname: Hart
authors.forename: U
authors.initials: U
authors.lastname: Khatwa
authors.forename: S
authors.initials: S
authors.lastname: Nurko
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D050782:Esophageal pH Monitoring; D005260:Female; D005764:Gastroesophageal Reflux / Q000175:diagnosis* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007223:Infant; D008168:Lung / Q000378:metabolism*; D008297:Male; D010434:Pepsin A / Q000235:genetics / Q000378:metabolism*; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity; D055815:Young Adult
chemical_list: D010434:Pepsin A