Pulmonary emphysema: Subjective visual grading versus objective quantification with macroscopic morphometry and thin-section CT densitometry

PURPOSE: To compare subjective visual grading of pulmonary emphysema with m acroscopic morphometry and computed tomographic (CT) densitometry. MATERIALS AND METHODS: In 62 consecutive patients who underwent thin-sectio n CT before surgical lung resection, emphysema was objectively quantified w ith computer-assisted macroscopic morphometry and CT densitometry. The perc entage of lung macroscopically occupied by emphysema was compared with the percentage occupied on CT scans by pixels with attenuation values lower tha n a predefined threshold (CT densitome), Three readers with varying degrees of expertise subjectively graded emphysema with visual assessment at two r eading sessions. Data from objective quantification and subjective grading were analyzed with correlation coefficients, and interobserver and intraobs erver agreement were calculated. RESULTS: Subjective grading of emphysema showed less agreement with the mac roscopic reference standard results (r = 0.439-0.505; P <.05) than with obj ective CT densitometric results (r = 0.555-0.623; P < .001). The 95% Cls fo r the intercepts of the linear regression lines were suggestive of systemat ic subjective overestimation of;emphysema by all three readers. lnterobseve r agrement was moderate (K = 0.431-0.589). Intraobserver agreement was good to excellent (K = 0.738-0.936). The expertise of individual readers did no t substantially influence results. CONCLUSION: Systematic overestimation and moderate interobserver agreement may compromise subjective visual grading of emphysema, which suggests that subjective visual grading should be supplemented with objective methods to achieve precise, reader-independent quantification of emphysema.