The DiPEP study: an observational study of the diagnostic accuracy of clinical assessment, D-dimer and chest x-ray for suspected pulmonary embolism in pregnancy and postpartum

Abstract

Objective: To identify clinical features associated with pulmonary embolism (PE) diagnosis and determine the accuracy of decision rules and D-dimer for diagnosing suspected PE in pregnant/postpartum women. Design: Observational cohort study augmented with additional cases. Setting: Emergency departments and maternity units at eleven prospectively recruiting sites and maternity units in the United Kingdom Obstetric Surveillance System (UKOSS). Population: 324 pregnant/postpartum women with suspected PE and 198 pregnant/postpartum women with diagnosed PE. Methods: We recorded clinical features, elements of clinical decision rules, D-dimer measurements, imaging results, treatments and adverse outcomes up to 30 days. Main outcome measures: Women were classified as having PE on the basis of imaging, treatment and adverse outcomes by assessors blind to clinical features and D-dimer. Primary analysis was limited to women with conclusive imaging to avoid work-up bias. Secondary analyses included women with clinically diagnosed or ruled out PE. Results: The only clinical features associated with PE on multivariate analysis were age (odds ratio 1.06; 95% confidence interval 1.01–1.11), previous thrombosis (3.07; 1.05–8.99), family history of thrombosis (0.35; 0.14–0.90), temperature (2.22; 1.26–3.91), systolic blood pressure (0.96; 0.93–0.99), oxygen saturation (0.87; 0.78–0.97) and PE-related chest x-ray abnormality (13.4; 1.39–130.2). Clinical decision rules had areas under the receiver-operator characteristic curve ranging from 0.577 to 0.732 and no clinically useful threshold for decision-making. Sensitivities and specificities of D-dimer were 88.4% and 8.8% using a standard threshold and 69.8% and 32.8% using a pregnancy-specific threshold. Conclusions: Clinical decision rules and D-dimer should not be used to select pregnant or postpartum women with suspected PE for further investigation. Clinical features and chest x-ray appearances may have counter-intuitive associations with PE in this context. Tweetable abstract: Clinical decision rules and D-dimer are not helpful for diagnosing pregnant/postpartum women with suspected PE.