Only two radiographic findings allow reliable distinction of benign from malignant solitary pulmonary nodules. Intuitively, it is clear that other radiographic and clinical findings should also be important in making this distinction. Subjectively incorporating these other findings into the decision of whether a nodule is benign or malignant is difficult. Likelihood ratios, which indicate the degree of malignancy or benignity represented by a test result or clinical finding, can be combined by means of the Bayes theorem to quantitate the probability of malignancy of a given nodule. From a literature survey, likelihood ratios were derived for six radiographic and four clinical characteristics associated with solitary pulmonary nodules. There were a total of 15 malignant and 19 benign findings, the most important of which were radiographic characteristics. For malignant nodules, the most important radiographic characteristics were thickness of the cavity wall spicular edge, and diameter of over 3 cm. For benign nodules, the most important radiographic characteristics were benign growth rate and a benign pattern of calcification.

High-resolution computed tomography (CT) was correlated with pulmonary function tests in the evaluation of regional emphysema in 59 smokers. The lung was divided into upper (above the carina tracheae) and lower (below the carina tracheae) zones, and the degree of emphysema was graded with a subjective and an objective measurement. Functional emphysema was defined as a diffusion capacity less than 75% of predicted and forced expiratory volume in 1 second less than 80% of predicted. Three of 15 (20%) subjects with functional emphysema had no subjective evidence of emphysema at high-resolution CT, and 10 of 25 (40%) with emphysema at high-resolution CT had no functional abnormalities consistent with emphysema. Even though the upper lung zones were more severely affected by emphysema, the degree of emphysema in the lower zones had a stronger correlation with pulmonary function abnormalities. The upper lung zones are a relatively silent region where extensive destruction may occur before functional abnormalities become known.

Four board-certified radiologists estimated the probability of malignancy in 66 cases of solitary pulmonary nodules. Two other radiologists evaluated the same nodules according to various radiographic and clinical findings. These findings were then used to estimate the probability of malignancy by using previously derived likelihood ratios and the Bayes theorem. The readers using Bayesian analysis performed significantly better than the expert readers (P < .05) when individual radiographs were considered and when all radiologic studies were combined. In addition, the readers using Bayesian analysis misclassified fewer malignant nodules as benign (mean, 6.5) than did the expert readers (mean, 6.5) than did the expert readers (mean, 16.5). The authors conclude that Bayesian analysis may be a useful aid in the evaluation of solitary pulmonary nodules.

A matched case-controlled study was conducted to determine if airway obstruction or emphysema were associated with an increased risk of lung cancer.Lung cancer cases (n=24) were identified through a low-dose spiral computed tomography (CT) screening trial from 1,520 participants. Four controls without lung cancer were selected for each case from the participants and matched by sex, age and smoking history. Emphysema was assessed by quantitative CT analysis. Conditional logistic regression was employed to assess results of spirometry and CT quantitative analysis as potential risk factors for lung cancer.The likelihood of lung cancer was found to be significantly increased for those with forced expiratory volume in one second (FEV1) ¡40% of predicted. The results suggested that a lower percentage of predicted FEV1 was indicative of lung cancer. No compelling evidence was found to suggest that the percentage of emphysema was associated with lung cancer.These results suggest an increased risk of lung cancer associated with airway obstruction. However, percentage of emphysema as determined by computed tomography was not associated with an increased risk of lung cancer.

Allergic bronchopulmonary aspergillosis (ABPA) is a destructive disease of the lung characteristically associated with central bronchiectasis. This study was designed to determine if high-resolution computerized tomography (CT) could be used to define bronchiectasis in patients with suspected disease. Sixteen patients with asthma were studied. All demonstrated immediate cutaneous reactivity to common aeroallergens including Aspergillus fumigatus. Eight patients had clinical and immunologic evidence of ABPA. Six to 12 high-resolution CT sections (1.5 mm) were obtained at 1- to 2-cm intervals from the aortic knob to the dome of the diaphragm. All radiographs were evaluated separately by two readers in a blinded fashion and graded as to the presence and type of bronchial dilatation and bronchial wall thickening. Bronchial dilatation was seen in 41% of lung lobes in the ABPA group compared to 15% in the non-ABPA asthmatic control group. Upper lobe involvement and bronchial wall thickening was common to both groups. The presence of bronchiectasis in the control group may indicate that asthma is a more destructive lung disease than is currently appreciated. High-resolution CT of the chest has been shown in previous studies to have a sensitivity and specificity approaching that of bronchography, and the current findings support its use in the detection of bronchiectasis in patients with asthma suspected of having ABPA.