title: Validation and development of an immunonephelometric assay for the determination of alpha-1 antitrypsin levels in dried blood spots from patients with COPD.
abstract: To validate and develop an immunonephelometric assay for the determination of alpha-1 antitrypsin (AAT) levels in dried blood spots from COPD patients in Brazil.
  
  
  
  We determined AAT levels in serum samples and dried blood spots from 192 COPD patients. For the preparation of dried blood spots, a disk (diameter, 6 mm) was placed into a tube, eluted with 200 µL of PBS, and stored overnight at 4ºC. All of the samples were analyzed by immunonephelometry in duplicate. We used the bootstrap resampling method in order to determine a cut-off point for AAT levels in dried blood spots.
  
  
  
  The correlation coefficient between the AAT levels in serum samples and those in dried blood spots was r = 0.45. For dried blood spots, the cut-off value was 2.02 mg/dL (97% CI: 1.45-2.64 mg/dL), with a sensitivity, specificity, positive predictive value, and negative predictive value of 100%, 95.7%, 27.2%, and 100%, respectively.
  
  
  
  This method for the determination of AAT levels in dried blood spots appears to be a reliable screening tool for patients with AAT deficiency.
authors: Universidade Federal de São Paulo, Department of Pulmonology, Pulmonary Rehabilitation Center, São Paulo, Brazil.
authors: Laura Russo
authors: LR
authors: Zillmer
authors: Rodrigo
authors: R
authors: Russo
authors: Beatriz Martins
authors: BM
authors: Manzano
authors: Ivan
authors: I
authors: Ivanaga
authors: Oliver Augusto
authors: OA
authors: Nascimento
authors: Altay Alves Lino de
authors: AA
authors: Souza
authors: Gildo
authors: G
authors: Santos
authors: Francisco
authors: F
authors: Rodriguez
authors: Marc
authors: M
authors: Miravitlles
authors: José Roberto
authors: JR
authors: Jardim
mesh_terms: D000368:Aged; D001938:Brazil; D003430:Cross-Sectional Studies; D059788:Dried Blood Spot Testing / Q000379:methods*; D005260:Female; D006801:Humans; D007159:Immunologic Tests / Q000379:methods*; D008297:Male; D008403:Mass Screening; D008875:Middle Aged; D009391:Nephelometry and Turbidimetry / Q000379:methods*; D010045:Outpatients; D011237:Predictive Value of Tests; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis*; D012015:Reference Standards; D000515:alpha 1-Antitrypsin / Q000097:blood*; D019896:alpha 1-Antitrypsin Deficiency / Q000175:diagnosis*
chemical_list: D000515:alpha 1-Antitrypsin