title: Utility of exhaled breath condensate pH for diagnosing occupational asthma.
abstract: BACKGROUND
  The current reference standard method for diagnosing occupational asthma (OA) is specific inhalation challenge (SIC) with the suspected agent. The alternative method is serial peak expiratory flow (PEF) monitoring. Nevertheless, PEF does not have optimal sensitivity and specificity for this purpose. The aim of this study was to evaluate the utility of exhaled breath condensate (EBC) pH for the diagnosis of OA.
  
  
  METHODS
  A prospective study was performed in 37 subjects with suspected OA. Serial PEF monitoring was carried out for 2 weeks at work and for 2 weeks off work. At the end of each period, the EBC pH and the methacholine concentration resulting in a 20% FEV(1) decrease (PC20) were measured. SIC was subsequently performed. PEF graphs were interpreted visually by 3 experienced independent readers.
  
  
  RESULTS
  Seventeen patients tested positive with SIC. Receiver-operating characteristic curves showed that a decrease in EBC pH greater than 0.4 units during the period at work compared to the off-work period achieved the most satisfactory sensitivity (40%, CI 19.4-66.5) and specificity (90%, CI 66.9-98.2) for diagnosing OA. When EBC pH findings were added to PEF results, the diagnostic yield of PEF generally increased. Other test combinations (e.g. EBC pH plus PC20 or EBC pH plus PC20 plus PEF) did not improve diagnostic performance.
  
  
  CONCLUSIONS
  Acidification of EBC pH at work and adding the EBC pH measurement to PEF monitoring during periods at work and off work may be useful for improving the diagnosis of OA.
authors: Servei de Pneumologia, Hospital Vall d'Hebron, Universidad Autònoma de Barcelona, Barcelona, Spain. xmunoz @ vhebron.net
authors: X
authors: X
authors: Muñoz
authors: M I
authors: MI
authors: Velasco
authors: M
authors: M
authors: Culebras
authors: O
authors: O
authors: Roca
authors: F
authors: F
authors: Morell
authors: M J
authors: MJ
authors: Cruz
mesh_terms: D000280:Administration, Inhalation; D000328:Adult; D059366:Asthma, Occupational / Q000175:diagnosis* / Q000209:etiology / Q000276:immunology / Q000378:metabolism; D001944:Breath Tests / Q000379:methods*; D001985:Bronchial Provocation Tests; D045853:Exhalation / Q000276:immunology*; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008297:Male; D016210:Methacholine Chloride / Q000378:metabolism; D008875:Middle Aged; D016273:Occupational Exposure / Q000009:adverse effects; D010366:Peak Expiratory Flow Rate; D011446:Prospective Studies; D012680:Sensitivity and Specificity
chemical_list: D016210:Methacholine Chloride