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Question 122
Delivery suite → Haemorrhage
Classification
Question
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A woman at 35 weeks has painful APH and uterine tenderness. Ultrasound shows no retroplacental clot. The reported sensitivity of ultrasound for detecting retroplacental clot in placental abruption is approximately 24%, although specificity is high. Which interpretation is most appropriate?
Question Stem
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Options
A
A) A negative scan substantially lowers the probability of abruption because specificity is high
B
B) A negative scan has limited value for excluding abruption because the test has poor sensitivity
C
C) High specificity means that ultrasound should replace clinical assessment when the scan is negative
D
D) The diagnosis of abruption requires ultrasound evidence when the placenta is posterior
E
E) Repeat ultrasound after 24 hours is required before abruption can be diagnosed clinically
Explanation
A test with poor sensitivity generates a substantial proportion of false-negative results. Therefore, ultrasound detection of a retroplacental clot has limited ability to exclude placental abruption when the scan is negative. High specificity is more useful when an abnormality is actually demonstrated; it does not make a negative result reassuring when sensitivity is only about 24%. Consequently, placental abruption remains a clinical diagnosis, and management should be determined by the maternal and fetal clinical picture rather than a negative ultrasound.
Option Validity
A) High specificity does not compensate for poor sensitivity when interpreting a negative test.
C) Poor sensitivity prevents ultrasound from replacing clinical assessment for exclusion of abruption.
D) Ultrasound demonstration of a retroplacental clot is not required to establish the clinical diagnosis.
E) Diagnosis and necessary management should not be delayed pending repeat imaging when the clinical presentation supports abruption.
Further Reading
RCOG Green-top Guideline No. 63. Antepartum Haemorrhage. Royal College of Obstetricians and Gynaecologists; 2011.