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Table 3 Performance of STI risk score at different cut-points

From: Identifying youth at high risk for sexually transmitted infections in community-based settings using a risk prediction tool: a validation study

  Cutpoint 19 Cutpoint 23
  % (n/N) 95% CI % (n/N) 95% CI
Sensitivity 82.4% (140/170) 75.8, 87.8 75.9% (129/170) 68.7, 82.1
Specificity 45.6% (359/787) 42.1, 49.2 59.3% (467/787) 55.8, 62.8
Yield 24.7% (140/568) 21.2, 28.4 28.7% (129/449) 24.6, 33.2
Efficiency 59.4% (568/957) 56.2, 62.5 46.9% (449/957) 43.7, 50.1
NNT 4.1   3.5  
  1. Efficiency = proportion of population that is tested
  2. NNT = number needed to test to obtain one positive result