After assay validation, which included the testing of various mutations and sample types, the PLx assay for CFTR gene analysis was directly compared with the CF Gold linear array method. Using freshly obtained blood cards from newborns that had immunoreactive trypsinogen scores in the upper 4%, we used both tests to analyze CFTR for the recommended core panel of mutations and reflex targets. The testing was performed on 419 samples, and 100% concordance was recorded (no incorrect assignments; Table 1 , column B). Of the samples tested, there were 21 samples (5%) in which the complete lists of calls could not be obtained with the PLx system. The failure rate of 5% was documented as errors resulting from pipetting errors. These samples were retested, and correct assignments were made. Of the possible 12 570 potential assignments, 12 521 (99.6%) were correct. Run time after sample preparation for the CF Gold test was ϳ7 h compared with Ͻ3 h for the PLx system. Total hands-on time for the CF Gold test was ϳ3.5 h compared with 0.5 h for the PLx system. The data output for the CF Gold test was visual inspection of the nitrocellulose strips, whereas the PLx system has a computerized calling system as described.