title: Faecal elastase-1: lyophilization of stool samples prevents false low results in diarrhoea.
abstract: BACKGROUND
  In patients with diarrhoea, faecal elastase-1 is used to detect exocrine pancreatic insufficiency. Diarrhoea is defined as >85% stool water content.
  
  
  METHODS
  We analysed elastase-1 in 519 stool samples from 310 patients unprocessed as well as after lyophilization in a standard laboratory lyophilizator. Stool water content was calculated by weight difference before and after lyophilization.
  
  
  RESULTS
  151 stool samples were classified as 'diarrhoea' (mean stool water content 88.8%); all others had a mean water content of 75.4%. In the 'diarrhoea' samples, elastase-1 levels were considerably higher after lyophilization--with a calculated normal water content of 75% (606 +/- 359 microg/g, mean +/- s)--compared to measurement when unprocessed (279 +/- 151 microg/g; P < 0.0001). In 16 of the 151 cases (11%), the abnormally low elastase-1 level below 200 microg/g found in unprocessed stools proved normal (>200 microg/g) after lyophilization and correction for stool water content.
  
  
  CONCLUSIONS
  Diarrhoea can result in falsely decreased elastase-1 levels in a number of patients with non-pancreatogenic diarrhoea. Lyophilization is a simple measure by which to determine elastase-1 independently of stool water content. Lyophilization of stool samples can therefore help to prevent wrong positive elastase-1 test results.
authors.affiliation: Dept. of Medicine 1, University of Erlangen-Nürnberg, Erlangen, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Fischer
authors.forename: S
authors.initials: S
authors.lastname: Hoh
authors.forename: M
authors.initials: M
authors.lastname: Wehler
authors.forename: E G
authors.initials: EG
authors.lastname: Hahn
authors.forename: H T
authors.initials: HT
authors.lastname: Schneider
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D003967:Diarrhea / Q000209:etiology*; D010188:Exocrine Pancreatic Insufficiency / Q000150:complications* / Q000175:diagnosis* / Q000201:enzymology; D005189:False Positive Reactions; D005243:Feces / Q000737:chemistry* / Q000201:enzymology*; D005260:Female; D005612:Freeze Drying / Q000379:methods* / Q000592:standards*; D006801:Humans; D007223:Infant; D008297:Male; D008875:Middle Aged; D010196:Pancreatic Elastase / Q000032:analysis*; D010186:Pancreatic Function Tests / Q000379:methods* / Q000592:standards*; D012680:Sensitivity and Specificity; D014867:Water / Q000032:analysis
chemical_list: D014867:Water; D010196:Pancreatic Elastase