title: Are the enzymatic methods currently being used to measure bronchoalveolar lavage bile salt levels fit for purpose?
abstract: BACKGROUND
  Microaspiration after gastroesophageal reflux has been implicated in the chronic loss of allograft function in lung transplant patients. Bronchoalveolar lavage fluid (BALF) assessment for pepsin and bile salts is a common method to document reflux and aspiration. Clinically used methods for bile salt analysis include tandem mass spectrometry and diagnostic enzymatic kits designed to measure bile salts in serum. In clinical research, the enzymatic kits have been commonly used for BALF assays in lung transplant recipients, with reports of detection limits of 0.2 μmol/liter, and the levels used to inform clinical decisions. This study assessed the sensitivity of detection by 2 enzymatic assay kits compared with tandem mass spectrometry.
  
  
  METHODS
  These 2 kits were used to measure (1) the absorbance changes for 0 to 50 μmol/liter bile salts, (2) levels in gastric juice (10-10,010 μmol/liter), and (3) bile salt levels of 40 BALF samples that were also measured using tandem mass spectrometry (0.01-1.19 μmol/liter). Measurements of pH/impedance were done in 14 of 15 patients.
  
  
  RESULTS
  Neither kit had detection limits as low as claimed in previous BALF studies. The kits could be made more sensitive with a longer incubation time, (5 μmol/liter). All patients had detectable lavage bile acids using mass spectroscopy, 71% had pathologic distal gastroesophageal reflux, and 43% had pathologic proximal reflux.
  
  
  CONCLUSIONS
  The enzymatic kits are not sensitive enough for use in situations where bile salt levels are much below 5 μmol/liter, which is the case in BALF. In addition, reports in the literature of levels significantly below 5 μmol/liter need reassessing. Tandem mass spectrometry with a lower limit of detection of 0.01 μmol/liter should be the method of choice.
authors: Institute for Cell and Molecular Biosciences, Newcastle University, Faculty of Medical Sciences, Newcastle upon Tyne, UK. shruti.parikh@ncl.ac.uk
authors: Shruti
authors: S
authors: Parikh
authors: Iain A
authors: IA
authors: Brownlee
authors: Andrew G
authors: AG
authors: Robertson
authors: Nigel T
authors: NT
authors: Manning
authors: Gail E
authors: GE
authors: Johnson
authors: Malcolm
authors: M
authors: Brodlie
authors: Paul A
authors: PA
authors: Corris
authors: Chris
authors: C
authors: Ward
authors: Jeffrey P
authors: JP
authors: Pearson
mesh_terms: D000328:Adult; D001647:Bile Acids and Salts / Q000032:analysis*; D018893:Bronchoalveolar Lavage; D004796:Clinical Enzyme Tests / Q000379:methods*; D006801:Humans; D008875:Middle Aged; D012680:Sensitivity and Specificity; D053719:Tandem Mass Spectrometry; D055815:Young Adult
chemical_list: D001647:Bile Acids and Salts