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A new study published in the Journal of Nuclear Medicine indicates that ventilation perfusion lung scanning (V/Q scans) are as effective as CT angiograms to rule out the pulmonary embolism (PE) in young women.

The team used data collected from the Prospective Investigation of Pulmonary Embolism Diagnosis II (PIOPED II) project to evaluate their hypothesis that very low probability interpretation of V/Q scans, if proven to have a low value for positive predictive value, can reduce the number of nondiagnostic interpretations of V/Q scans.

Factors that are considered low level indicators include:

• abnormalities in segmental perfusion,
• perfusion defect smaller than the associated lesion on radiography,
• > 2 matched V/Q defects and chest radiography that is regionally normal,
• 1-3 small segmental perfusion defects,
• solitary triple matched defect in either upper or middle lung zones,
• stripe sign around the perfusion defect or defects, and
• defects from pleural effusion equal to one third or more of the pleural cavity with no other defects in perfusion.

Radiologists agreed that 56 percent of the patient studies had very low probability according to the V/Q scan. The associated positive predictive value (PPV) was 8.2 percent or 36/440. Patients who had a low clinical probability from objective clinical assessment and a very low probability from the V/Q scan had a positive predictive value of 3.1 percent or 8/259 patients. Specifically among women less than 40 years old, the PPV was two percent.

These factors, in conjunction with an objective clinical assessment with a low level of probability suggesting a pulmonary embolism, are thought to be indicators for assessment with V/Q scans rather than CT angiograms. This test is already indicated for patients with a contraindication to CT scanning. The new data verifies the validity of this alternative approach.

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September 20, 2007 Related topics: Pulmonary, Imaging, Diagnostic, Radiology