Ultrasound, hormonal marker help diagnose ectopic pregnancies

October 13, 2004

Ultrasound-based techniques in combination with a hormonal index marker can either confirm or rule out ectopic pregnancies, according to several papers presented in June at the American Institute of Ultrasound in Medicine meeting in Phoenix, Arizona.

Ultrasound-based techniques in combination with a hormonal index marker can either confirm or rule out ectopic pregnancies, according to several papers presented in June at the American Institute of Ultrasound in Medicine meeting in Phoenix, Arizona.

Harvard University researchers evaluated the appearance and size of the intradecidual sign in combination with the human chorionic gonadotropin (hCG) marker for the accurate diagnosis of ectopic pregnancies. In a retrospective review of 187 pregnant women with the intradecidual sign on intrauterine ultrasound, they found that the sign reliably excluded the presence of an ectopic pregnancy.

Women with confirmed intradecidual signs showed no ectopic pregnancies. Those with an intradecidual sign diameter or an hCG level equal to or larger than 3 mm or 2000 mIU/mL, respectively, showed a prevalent diagnosis of intrauterine pregnancies.

Three independent readers checked intradecidual signs-endometrial fluid collections with a slightly echogenic rimlike appearance lacking a yolk sac or embryo-using four different ultrasound views for each case. They subsequently scored intradecidual signs on a five-point scale, with five meaning the sign was definitely present and one meaning it was definitely absent.

"It's really important to assess the presence of this sign on multiple ultrasound views with an unchanging appearance," said principal investigator Gloria Chiang from Harvard.

British investigators also assessed the value of the hCG marker in combination with ultrasound assessments. Dr. Emma Kirk from St. Georges Hospital Medical School in London presented results of a study that included 388 consecutive patients with pregnancies of unknown location. The investigators used data from 185 patients to develop a novel index they called the hCG ratio. They subsequently tested the hCG ratio in the remaining 196 patients to detect failing or successful intrauterine pregnancies and ectopic pregnancies. They found that the hCG ratio can be used to determine whether a pregnancy of unknown location is either ectopic or a failing intrauterine pregnancy.

An hCG ratio of more than 1.66 provided sensitivity, specificity, and positive and negative predictive values of 85.7%, 96.6%, 94.3%, and 91.3%, respectively, for detection of intrauterine pregnancies. An hCG ratio less than 0.8 yielded sensitivity, specificity, PPV, and NPV of 88.8%, 97.8%, 97.9%, and 87.9%, respectively, for failing pregnancies. An hCG ratio between 0.8 and 1.66 gave a sensitivity, specificity, PPV, and NPV of 75%, 89.1%, 31%, and 98.2%, respectively, for ectopic pregnancies.

The British researchers reviewed results from yet another study considering sonography and hCG levels in 5544 consecutive patients. They used three discriminatory zones (hCG > 1000, 1500, and 2000 U/L) to detect ectopic pregnancies in these women. They found that varying the discriminatory zone does not significantly improve ectopic pregnancy detection.

The group warned that hCG levels, though useful, cannot be used alone to diagnose ectopic pregnancies.

"Ultrasound, not biochemistry, is the most important first-line diagnostic tool in ectopic pregnancies," Kirk said.