CLINICIAN INTERPRETATION OF THE INDETERMINATE VENTILATION-PERFUSION SCAN REPORT

Most patients with suspected pulmonary embolism are initially investig ated by radionuclide ventilation-perfusion (VQ) scanning. Approximatel y 70% of VQ scans are ''indeterminate'' Further investigations should be considered in such patients in order to establish a definitive diag nosis. However, these investigations are rarely requested in patients with indeterminate scans in our institution. We therefore decided to r eview the casenotes of such patients to determine their ent. Over a 9 month period, 131 (32%) out of a total of 413 consecutive VQ scans wer e reported as indeterminate. The casenotes of 111 of these patients (6 5 female, 46 male, mean age 65 years, range 17-91 years) were reviewed . 52 of the 111 patients (46%) were treated on clinical grounds withou t further investigation; 12 patients (11%) had further investigation; and in 39 of the cases (35%) the VQ scan report was misinterpreted. 20 (38%) of the 52 patients managed on clinical grounds were treated for pulmonary embolus with anticoagulation and 26 (50%) were not anticoag ulated. Of the 12 patients who were investigated further, nine had low er limb Doppler ultrasound and three had contrast venography. No patie nts had pulmonary angiography. Of the 39 cases where the VQ report was misinterpreted, the result was misquoted in the casenotes of 37 (95%) as negative for PE and none of these patients were anticoagulated, an d in two cases (5%) it was misquoted as positive for PE and anticoagul ant therapy was instituted. The misunderstanding was observed in all c linical firms. Such misinterpretation may have significant implication s, since 30-40% of patients with indeterminate scans may have had PE. Our findings suggest that clinicians need to be better informed of the significance of an indeterminate VQ scan result.