Lung scan interpretation: a physiologic, user-friendly approach

A physiologically-oriented, user-friendly algorithm for interpretation of ventilation-perfusion (V/P) lung scans was compared to the widely used Biello criteria. The physiologic algorithm relies primarily on the observer's degree of certainty that a V/P mismatch is present rather than on the size (relative to a whole segment) and number of V/P mismatches. One hundred five patients who had undergone a ventilation study with 133Xe gas, a perfusion study with 99mTc-MAA and pulmonary angiography were reviewed. Each V/P lung scan was interpreted once with the physiologic algorithm and once with the Biello criteria by two observers. Fifty-nine percent of the 105 studies were classified as indeterminate with the physiologic algorithm versus 62% with the Biello criteria. The prevalence of pulmonary embolism in the high probability, indeterminate, low probability and normal categories for the physiologic algorithm were 60%, 26%, 7% and 0%, respectively; and for the Biello criteria were 50%, 31%, 11% and 0%, respectively. Analysis of the data with receiver-operating-characteristic curves indicated that the physiologic algorithm performed better than the Biello criteria (p less than 0.05). In addition, the physiologic algorithm has the advantages of being more intuitive and easier to remember. We conclude that further evaluation of the physiologic approach for the interpretation of V/P lung scans is warranted.