An evaluation of the shock index in predicting ruptured ectopic pregnancy

In order to evaluate the shock index in predicting a ruptured ectopic pregnancy in a Nigerian obstetric population, a prospective observational study of consecutive pregnant women presenting to the emergency room of the University of Nigeria Teaching Hospital, Enugu with complaints of abdominal pain and/or vaginal bleeding in the first trimester of pregnancy over a 23-month period (1 February 2003 to 31 December 2004) was carried out. A total of 152 subjects were studied. Of these, 15 (9.9%) of the women had ruptured ectopic pregnancy while the rest had other causes of bleeding in early pregnancy. The mean shock index for ruptured ectopic pregnancy was significantly different from that for threatened abortion (p < 0.001), incomplete abortion (p = 0.022) and inevitable abortion (p < 0.001) but not from that for unruptured ectopic pregnancy and septic abortion (p > 0.05 for both categories). The areas under the relative operating characteristic (ROC) curves for shock index and heart rate were statistically significant (p < 0.001 for both variables) but those under the curves for systolic blood pressure, diastolic blood pressure and mean arterial blood pressure were not statistically significant (p > 0.05 for the three variables). From the curves, the cut-offs that combined highest sensitivity with lowest false positivity (1-specificity) were 0.935 for the shock index and 99 bpm for heart rate. On univariate logistic regression, the odds ratio (OR) for predicting ruptured ectopic pregnancy was 52.9 (95% CI = 10.9 - 257.3, p < 0.001) for shock index > or =0.935 and 26.4 (95% CI = 6.8 - 102.8, p < 0.001) for heart rate > or =99/min. On multivariate logistic regression using both shock index > or =0.935 and heart rate > or =99/min, only shock index > or =0.935 was statistically significant with an OR of 4.5 (95% CI = 1.8 - 11.6, p = 0.002). We conclude that when faced with the possibility of ruptured ectopic pregnancy, shock index has a high predictive value in the Nigerian population studied and is a useful addition to the currently available diagnostic armamentarium in ruptured ectopic pregnancy.