Patterns of pulmonary perfusion scans in normal subjects.

The prevalence of abnormal pulmonary perfusion (Q) scans in persons without cardiopulmonary disease could condition the usefulness of the Q scan in the evaluation of patients in whom pulmonary embolism is suspected. In a recent study, we found that Q scan defects, particularly lobar or segmental defects, are rarely present in normal young nonsmokers. To determine if normal smokers of the same age group have a higher prevalence of Q defects, we performed 6 view Q scans in 40 subjects 18 to 29 yr of age who had no known active cardiopulmonary disease. Each subject had undergone a history, physical examination, electrocardiogram, spirometry, and posteroanterior chest roentgenogram prior to scanning. All Q scans were interpreted blindly and independently by 2 experienced readers. None of the 40 subjects was found to have an abnormal Q scan defined as the presence of a lobar, segmental, or subsegmental defect on 2 views. When these data were compared with our previous study, statistical analysis found no difference in the prevalence of abnormal Q scans in the 2 groups. We conclude that among young normal persons, abnormal Q scans are extremely uncommon and the prevalence of significant Q defects is not influenced by smoking.