Elsevier

Academic Radiology

Volume 21, Issue 1, January 2014, Pages 3-10
Academic Radiology

Original Investigation
Impact of Body Mass Index on the Detection of Radiographic Localized Pleural Thickening

https://doi.org/10.1016/j.acra.2013.09.014Get rights and content

Rationale and Objectives

Subpleural fat can be difficult to distinguish from localized pleural thickening (LPT), a marker of asbestos exposure, on chest radiographs. The aims of this study were to examine the influence of body mass index (BMI) on the performance of radiograph readers when classifying LPT and to model the risk of false test results with varying BMI.

Materials and Methods

Subjects (n = 200) were patients being screened or treated for asbestos-related health outcomes. A film chest radiograph, a digital chest radiograph, and a high-resolution computed tomography (HRCT) chest scan were collected from each subject. All radiographs were independently read by seven B readers and scored using the International Labour Office system. HRCT scans, read by three experienced thoracic radiologists, served as the gold standard for the presence of LPT. We calculated measures of radiograph reader performance, including sensitivity and specificity, for each image modality. We also used logistic regression to estimate the probability of a false-positive and a false-negative result while controlling for covariates.

Results

The proportion of false-positive readings correlated with BMI. While controlling for covariates, regression modeling showed the probability of a false-positive result increased with increasing BMI category, younger age, not having pleural calcification, and among subjects not reporting occupational or household contact asbestos exposure.

Conclusions

Clinicians should be cautious when evaluating radiographs of younger obese persons for the presence of asbestos-related pleural plaque, particularly in populations having an anticipated low or background prevalence of LPT.

Section snippets

Subjects and Radiologic Image Reading

Informed consent was obtained under an institutional review board–approved protocol. Subjects (n = 200) were participants of a study assessing film and digital radiographs to determine their comparability for the classification of pneumoconiotic pleural plaque (8). All were patients being treated or screened for asbestos-related health outcomes in Libby, Montana. Subjects were consecutive patients selected on the basis of having a retrospectively collected HRCT scan collected within 24 months

Results

Table 1 shows characteristics of subjects by BMI category. More than half of all subjects were obese (48%) or morbidly obese (9%) and none had a BMI <19 kg/m2. One hundred forty-three (72%) were male and the majority (n = 103; 52%) reported residential exposure only (i.e., no occupational or household contact exposure). Median age was about 10 years lower among subjects with a normal BMI compared with other BMI categories.

Table 2 shows the unadjusted performance of film and digital radiographs

Discussion

These results suggest that BMI can be a substantial factor influencing radiographic findings of LPT. Using HRCT as a gold standard and a modeling approach, we found a distinct trend of increasing probability of a false-positive result with increasing BMI. This result suggests that subpleural fat is more likely to have the appearance of LPT as a patient's BMI increases and may have medicolegal implications. Further, we observed an inverse relationship between the probability of a false-positive

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