Predictive values and likelihood ratios of historical variables for being not pregnant
| Historic variable | Negative HCG | NPV | LR- | 95% CI |
|---|---|---|---|---|
| *Likelihood ratio cannot be calculated as there were no positive results for subjects who stated they were not sexually active. | ||||
| †There were no cases in which the patient stated that she “might be” pregnant but that there was “no chance” she could be pregnant. | ||||
| CI, confidence interval; HCG, human chorionotropic gonadotropin; LMP, last menstrual period; LR-, negative likelihood ratio; NPV, negative predictive value. | ||||
| Not sexually active (n = 130) | 130 | 100.0% | * | * |
| No to “chance pregnant” (n = 337) | 336 | 99.7% | 0.13 | 0.02 to 0.82 |
| No to “might you be”†(n = 444) | 439 | 98.9% | 0.48 | 0.25 to 0.92 |
| Uses birth control (n = 231) | 228 | 96.1% | 0.47 | 0.18 to 1.25 |
| LMP normal (n = 349) | 343 | 96.0% | 0.74 | 0.43 to 1.27 |
| LMP on time (n = 361) | 356 | 94.9% | 0.59 | 0.38 to 1.13 |