title: Influence of storage time and temperature on pleural fluid adenosine deaminase determination.
abstract: OBJECTIVE
  The determination of adenosine deaminase (ADA) activity in pleural fluid is important for differentiation of pleural effusions and diagnosing pleural tuberculosis. Although measurement of ADA is simple and inexpensive, controversies exist regarding potential errors caused by time elapsed between sample collection and analysis, storage temperature and the use of anticoagulants. The objective of this study was to evaluate the influence of storage time (1, 3, 7, 10 and 28 days) and temperature (4 degrees C and -20 degrees C) on the determination of ADA in pleural fluid samples collected in EDTA and sent at ambient temperature to the laboratory for initial processing within 1 h of collection.
  
  
  METHODS
  Twenty-seven pleural exudates obtained from 20 patients with neoplastic disease and seven with tuberculosis were analysed. The ADA activity obtained within 1 h of collection was considered the gold standard and was compared with the other measurements.
  
  
  RESULTS
  The correlation between the initial measurement and all others was >or=0.90 for both temperatures up to the 10th day after thoracocentesis and tended to decrease by 28 days after collection, but this difference was not significant.
  
  
  CONCLUSIONS
  Pleural fluid samples collected in EDTA and sent for analysis within 1 h after collection can be used to determine ADA up to 28 days after collection if stored at 4 degrees C or -20 degrees C, with no evidence of significant increases or decrease in enzyme activity that might distort the results.
authors.affiliation: Laboratory of Pleura, Pulmonary Division, Heart Institute (InCor), University of São Paulo Medical School, São Paulo, Brazil.
authors.forename: Leila
authors.initials: L
authors.lastname: Antonangelo
authors.forename: Francisco S
authors.initials: FS
authors.lastname: Vargas
authors.forename: Luciana P
authors.initials: LP
authors.lastname: Almeida
authors.forename: Milena M P
authors.initials: MM
authors.lastname: Acencio
authors.forename: Fabrício D M
authors.initials: FD
authors.lastname: Gomes
authors.forename: Roberta K
authors.initials: RK
authors.lastname: Sales
authors.forename: Márcia
authors.initials: M
authors.lastname: Seicento
authors.forename: Lisete R
authors.initials: LR
authors.lastname: Teixeira
mesh_terms: D000243:Adenosine Deaminase / Q000032:analysis*; D004795:Enzyme Stability; D006801:Humans; D010996:Pleural Effusion / Q000201:enzymology*; D011309:Preservation, Biological; D013696:Temperature; D014396:Tuberculosis, Pleural / Q000175:diagnosis / Q000201:enzymology
chemical_list: D000243:Adenosine Deaminase