Validation of a Rapid, Simple Method to Measure α1-Antitrypsin in Human Dried Blood Spots

Screening for α1-antitrypsin deficiency (AATD) can be performed with dried blood spots (DBS) on filter paper, which allows quantification of AAT by immunonephelometry (1), identification of the AAT phenotype by isoelectric focusing(2)(3), and/or AAT genotyping (4). In most diagnostic flow-charts, important decisions often depend on the AAT concentration determined from DBS; however, current methods are imprecise, and results from DBS are not identical to those obtained using serum samples(4). We wished to develop a method for quantifying AAT in DBS. We collected 75 specimens from healthy blood donors and 74 from patients with suspected AATD. Samples were centrifuged for 8 min at 1620 g , and the serum or plasma, without manifest hemolysis, was separated and stored at −80 °C. Blood was spotted on filter paper with dashed-line 13-mm printed circles (Schleicher & Schuell Grade 903; lot. W-011) and air-dried. Cards stored in plastic bags at room temperature can be kept for at least 1 year. We measured AAT in serum or plasma by nephelometry (Array 360 System) with a polyclonal anti-human AAT goat antibody and calibrator (CAL2, assigned AAT …