This study summary is an excerpt from the book 2 Minute Medicine Classics of Medicine: Summaries of Landmark Trials
1. Sonographic demonstration of any non-cystic adnexal mass is both sensitive and specific for the diagnosis of ectopic pregnancy (EP) by transvaginal ultrasonography (TVUS).
2. Visualization of a noncystic adnexal mass is comparably specific to direct imaging of a live extrauterine pregnancy or gestational sac, but significantly more sensitive for PE.
Original publication date: April 1994
Study Summary: PE is a life-threatening obstetric emergency in which pregnancy occurs outside the uterus and often presents as an acute onset of pelvic pain with vaginal bleeding. Most PEs occur within the fallopian tube, but the embryo can also implant within the cervix, ovaries, or abdomen, requiring urgent laparoscopic removal at any of these locations. Accurate diagnosis includes both measurement of serum human chorionic gonadotropin levels to confirm pregnancy and ultrasonographic visualization of ectopic products of conception, as confirmed by the work of Shalev et al., Condous et al. and Grace and Barnhart. Once several studies confirmed the suitability of TVUS as the first-line study in the diagnosis of PE, the question arose as to what specifically should be visualized at the positivity threshold to diagnose PE more sensitively and specifically. The referenced study reviewed and analyzed the contemporary literature to determine which of the four criteria, in descending order of stringency, was most appropriate to use as a broad threshold for TVUS positivity in the diagnosis of PE. The four criteria reviewed were, at most, (1) direct visualization of a living extrauterine pregnancy, followed by (2) an extrauterine gestational sac with yolk sac or embryo, (3) an empty tubal ring or extrauterine fluid collection with a surrounding hyperechoic ring, or (4) any adnexal mass other than a simple cyst, allowing for the inclusion of a visualized hematoma in addition to any products of conception. The authors found that while the strictest criteria were the most specific (99-100%), they were highly insensitive (20-65%) and had only moderate negative predictive values (78-89%). The less stringent criterion traded a minimally reduced specificity (98.9%) for a significant improvement in sensitivity (84%) and negative predictive value (95%). Based on these criteria, the interpretation of TVUS in the diagnosis of PE was simplified, reducing failure to diagnose a potentially fatal condition while improving early recognition of PE and increasing opportunities for medical management with methotrexate over the condition. laparoscopic intervention. In particular, this study did not assess the effect on visualization of free fluid within the peritoneum, which can occur after PE rupture, but nevertheless established the most sensitive and specific criteria for interpreting TVUS in the diagnosis of PE.
in deep [systematic review and meta-analysis]: This systematic review and meta-analysis pooled data from studies published between 1986 and 1993 that examined the use of TVUS in the diagnostic work-up of patients with suspected PE. A total of 2216 patients (1651 with PE and 565 without) were included spanning 10 studies in which all enrolled patients were evaluated for TVUS in the PE study with subsequent surgical confirmation of all cases. Sensitivity, specificity, and positive and negative predictive values were calculated using Bayes’ theorem for each of the four different positivity criteria used as the diagnostic threshold in the evaluation of TVUS. Since EPs can be visualized as anything from an intact ectopic pregnancy to an adnexal hematoma or other complex adnexal mass, the four criteria tested sought to encompass a gradual progression in sonographic specificity as follows: the strictest criteria required visualization from an extrauterine embryo with a heartbeat (20.1% sensitivity, 100% specificity, NPV 78.5%); followed by extrauterine gestational sac with yolk sac or embryo (sensitivity 36.6%, specificity 100%, NPV 82.2%); an adnexal mass with a central anechoic region or hyperechoic rim, known as an “empty tubal ring” (64.6% sensitivity, 99.5% specificity, 89.1% NPV); or the less strict criterion, any adnexal mass that is not a simple cyst or intraovarian lesion (84.4% sensitivity, 98.9% specificity, NPV 94.8%). As the positivity threshold became less stringent, sensitivity increased dramatically, but with minimal decrease in overall specificity, and TVUS was found to perform better using the looser threshold when PE is suspected. This study established the simplest and most effective interpretation strategy for TVUS in the diagnosis of PE for both pre-surgical and medical management, and created an interpretive baseline for comparison with alternative diagnostic techniques.
Brown DL, Doublet PM. Transvaginal ultrasound for the diagnosis of ectopic pregnancy: positivity criteria and performance characteristics. JUM. April 1, 1994; 13(4): 259–66.
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