The utility of the wells clinical prediction model and ventilation-perfusion scanning for pulmonary embolism in pregnancy.

Abstract

Aim: To retrospectively evaluate the Wells clinical prediction model and ventilation-perfusion scanning (VQ) for Pulmonary Embolism (PE) in pregnancy. Method(s): A retrospective study was performed involving pregnant women who presented with suspected PE and underwent VQ scanning. The clinical pretest probability (PTP) was determined as low, intermediate or high by two independent assessors retrospectively. VQ scans were determined as normal, non-diagnostic or high probability for PE independently by two experienced radiologists. Disagreements were resolved by a third assessor independently. Result(s): Fifty pregnant women with suspected PE were evaluated. The median age was 30 years (range 17-44 years) 39 were in the third trimester. PTP was determined as low, intermediate or high in 7 40 and three patients respectively. VQ scans were determined as normal, non-diagnostic or high probability for PE in 44 four and two patients respectively. All three patients with high PTP had normal VQ scans and no venous thrombo-embolism (VTE) for the remainder of pregnancy. The two patients with high probability VQ scans had intermediate PTP and received anticoagulation. The four patients with non-diagnostic scans had low (2) or intermediate (2) PTP with no evidence of VTE on Doppler Ultrasound. A non-diagnostic CTPA was performed on one patient with an intermediate VQ scan. Modifying the Wells prediction model to PE 'Unlikely' or 'Likely' showed that the two women with high probability VQ scans now had a PTP of 'Likely'. However, 14 women with PE 'Likely' had normal VQ scans. Conclusion(s): (i) The prevalence of high probability VQ scans is very low; (ii) withholding anticoagulation in pregnant women, whose VQ scan results are normal or non-diagnostic appears to be safe; (iii) pregnant women with high-probability VQ scans likely have PE; (iv) a structured clinical model, other than Wells, may be necessary to ascertain PTP for PE during pregnancy. This needs to be further evaluated prospectively.