Table 1. The performance of three z score calculation methods for noninvasive detection of chromosome 21 trisomy.
| z score calculation method | 1* | 2* | 3* | |||
|---|---|---|---|---|---|---|
| Sensitivity | Specificity | Sensitivity | Specificity | Sensitivity | Specificity | |
| Ion Torrent PGM all reads | 100% (24/24) | 99.06% (105/106) | 100% (24/24) | 100% (106/106) | 100% (24/24) | 98.11% (104/106) |
| Ion Torrent PGM up to 160 bp reads | 100% (24/24) | 100% (106/106) | 100% (24/24) | 100% (106/106) | 100% (24/24) | 100% (106/106) |
| MiSeq all reads | 100% (24/24) | 100% (106/106) | 100% (24/24) | 99.06% (105/106) | 100% (24/24) | 100% (106/106) |
| MiSeq up to 155 bp reads | 100% (24/24) | 100% (106/106) | 100% (24/24) | 100% (106/106) | 100% (24/24) | 100% (106/106) |
*—1—the approach using reads mapped to all chromosomes utilized as a reference [17], 2—the approach using reads mapped to chromosome 14 as a reference [18] and 3—the approach using the reads mapped to optimal combination of chromosomes with the lowest coefficient of variance for reference samples [8, 19].