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. 2018 Jun 28;13(6):e0198777. doi: 10.1371/journal.pone.0198777

Fig 1. The sampling process is described in a STROBE flow chart.

Fig 1

A total of 17,893 clinical records of patients treated in outpatient respiratory clinics were evaluated during the study period and 5,726 clinical records of patients presumably diagnosed with COPD were selected. Of them, 4,508 patients were audited from 59 hospitals, for having all the inclusion criteria and none of the exclusion criteria. A total of 4408 patients audited from 57 hospitals with available AAT blood level determination were included for this retrospective analysis of alpha-1 antitrypsin deficiency diagnosis.