Intermediate Probability Lung Scans (IPLS): Retrospective Review of 82 Cases

WY Wong, DCE Ng, ES Ang, ASW Goh, FX Sundram
Correspondence: Dr W Y Wong

ABSTRACT
Objective In the light of a reported 30-40% prevalence of pulmonary embolism (PE) in intermediate probability lung scans (IPLS) based on results of the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) study, we examined the frequency of documented PE in 82 patients with IPLS, the management strategy employed in these patients with regards to additional imaging (e.g. further evaluation with venous sonography or spiral computed tomographic angiography (CTA)), anticoagulation therapy, and subsequent follow-up outcomes.
Method Retrospective review of the medical records of 82 patients with intermediate probability ventilation-perfusion (V/Q) lung scans from January 1998 to July 1999.
Results 14.1% of V/Q scans were reported as having an intermediate probability of PE. 72% of IPLS were subject to further evaluation with venous Doppler ultrasound and/or CTA, and 39% of these patients had evidence of thrombo-embolic disease. All patients with imaging evidence of thromboembolic disease were started on anticoagulation therapy. In addition, 19 patients were treated based on clinical judgement. Amongst the 35 patients who were not treated, 17 (49%) were based on clinical findings without further imaging. There was no mortality on follow-up of 28 cases of untreated IPLS.
Conclusion The majority of IPLS will have further imaging, out of which over one-third will have thrombo-embolic disease. Approximately half of IPLS cases will receive anticoagulation therapy. No mortality or PE was found on follow-up of patients who were not treated.

Keywords: pulmonary embolism, V/Q scan, intermediate probability, spiral CTA, Doppler ultrasound
Singapore Med J 2001; 42(10): 450-454