Table 2 Performance of reflex DNA screening using a 1 in 800 combined test risk cutoff to select women for a DNA test compared with women only receiving the combined test using a 1 in 150 risk cutoff

From: Prenatal reflex DNA screening for trisomies 21, 18, and 13

Screening method   Affected Unaffected a
  Trisomy Positive/total DR (95% CI) Positive/total FPR (95% CI) OAPR
Reflex DNA screening 21 69/73 95% (87–98%) 4/22,706 0.02% (0.00–0.05%) 17:1
  18 24/25 96% (80–100%) 0/22,706 0.00% (0.00–0.02%) >24:1
  13 8/8 100% (63–100%) 0/22,706 0.00% (0.00–0.02%) >8:1
  All 101/106 95% (89–98%) 4/22,706 0.02% (0.00–0.05%) 25:1
Combined test only 21 59/73 81% (70–89%) 532/22,706 2.34% (2.15–2.55%) 1:9
  18 20/25 80% (59–93%) 10/22,706 0.05% (0.02–0.08%) 1:2
  13 6/8 75% (35–97%) 55/22,706 0.24% (0.18–0.32%) 1:9
  All 86/106 81% (72–88%) 549/22,706 2.42% (2.22–2.62%) 1:6
  1. CI, confidence interval; DR, detection rate; FPR, false-positive rate; OAPR, odds of being affected given a positive result.
  2. aUnaffected with any of trisomy 21, 18, or 13.