Objective Although ventilation–perfusion scintigraphy (V/Q scan) is a robust and well established diagnostic test for suspected pulmonary embolism, false negative cases still exist. This study aimed to investigate the characteristics of false negative pulmonary embolism cases by V/Q scan.
Method During Jun 2008 to Apr 2010, patients with acute pulmonary embolism underwent both ventilation–perfusion scintigraphy (V/Q scan) and spiral CT pulmonary angiography (CTPA) were systematically reviewed. The patients were grouped by results of CTPA. Group 1: CTPA showed that the main pulmonary or lobe arteries were involved; Group 2: CTPA showed that the thrombi were limited to segmental or subsegmental pulmonary arteries. The characteristics of the false negative cases by V/Q scan were analysed.
Results In all 35 acute pulmonary embolism patients were included. There were 13 males (37.1%) and 22 females (62.9%) with a mean age of 59.3±15.0 years. The mean onset time of pulmonary embolism was 9.9±7.3 days and the mean interval time between V/Q scan and CTPA was 3.7±2.5 days. There were 1 (4.4%) false negative cases out of 23 patients by V/Q scan in group 1 and 4 (33.3%) false negative cases out of 12 patients in group 2 (p<0.001).
Conclusions The incidence of false negative cases in diagnosing acute pulmonary embolism by V/Q scan is increased significantly when CTPA showed that thrombi are limited to segmental or subsegmental and further branches of pulmonary arteries. In the clinical setting of highly suspected acute pulmonary embolism, even though the V/Q scan was negative, CTPA is needed for more diagnostic information.