Ability of a single negative ultrasound to rule out deep vein thrombosis in pregnant women: A systematic review and meta‐analysis

BACKGROUND: The diagnostic accuracy of ultrasound (US) for suspected lower extremity deep vein thrombosis (DVT) in nonpregnant patients has been well validated. However, in pregnant women with suspected DVT and an initial negative US, serial US is generally recommended. We aimed to determine the ability of single negative US to exclude DVT in symptomatic pregnant women. METHODS: Two authors independently reviewed the following databases: MEDLINE, PubMed, and EMBASE from inception until February 2019. We assessed the risk of bias using the CLARITY group tool for prognostic studies and performed a random effects meta-analysis to report the pooled false negative rate of a single leg ultrasound. RESULTS: Eight studies (seven prospective and one retrospective) were included. An overlap among study populations was identified in four of the manuscripts. Two authors performed data re-extraction from these hard copy research charts. Risk of bias was low for the included populations and method of measurement, and low or high for completeness of follow up. A total of 635 pregnant patients with symptoms of DVT had an initial negative US examination. Of those, six were diagnosed with DVT during repeat serial testing (0.94%) and three developed DVT or PE during 3-month follow-up after serial ultrasonography (0.47%). The pooled false-negative rate of a single ultrasound was 1.27% (95% confidence interval, 0.42-2.56), I²  = 27%. CONCLUSION: The false-negative rate is low with a single US for suspected DVT in pregnancy. Our results will help inform shared decision-making around planning repeat ultrasound scans in these patients.