Overstating the consequences of radiographic abnormalities.

"Radiographic Abnormalities and Exposure to Asbestos-Contaminated Vermiculite in the Community of Libby, Montana, USA" by Peipins et al. (2003) is the first journal publication by the Agency for Toxic Substances and Disease Registry (ATSDR) of the results of their multiyear medical testing program of Libby residents. Peipins et al.'s (2003) conclusion that 18% of study participants had pleural abnormalities has received wide attention and has lead to understandable concern among Libby residents and health professionals. We, as principals of Health Network America (HNA) and administrators of the Libby Medical Plan (LMP), are in the unique position of having participated in the peer review of applicants and members of the LMP. The LMP is a health benefit program for the people who lived in and around Libby and developed an asbestos-related condition. The peer reviewers include two board-certified radiologists who specialize in chest radiography and/or pneumoconiosis and are certified B-readers, and a third board-certified radiologist who specializes in interpretation of pleural disease on chest computed tomography (CT) scans. Although the review process is ongoing, some of our preliminary observations are relevant because they include many cases reported as "abnormal" by the ATSDR. In this letter we seek to communicate the more serious issues raised by this review process.

The basic ATSDR study design included a three-view chest X ray (posterior-anterior, left and right, and obliques) on all participants over 18 years of age, with the X rays to be interpreted by three B-readers. If two of the B-readers identified a pleural or interstitial abnormality, this would be regarded as a positive response by the ATSDR. If only one of the initial two B-readers identified an abnormality, the third B-reader also performed an interpretation.

Several problems are raised by this design. First, all B-readers were aware that the X rays were of Libby residents, opening the door to reader bias. Second, the B-readers knew the sequence in which they reviewed the films. B-readers 1 and 2 knew they were always the first or second reader. B-reader 3, then, not only knew the X rays were from Libby but also had the reports of B-readers 1 and 2 prior to making his interpretation. Although control films or a control group would have been useful in resolving these issues, they were not used.

Peipins et al. (2003) bolstered their findings with the assertion that "if two out of three B-readers indicated ...," implying agreement between these readers. The HNA's review (HNA. Unpublished data) reveals that in many instances this was not the case. For example, if one reader found a potential pleural plaque on the right chest wall and the second reader recorded a possible pleural plaque on the left chest wall or diaphragm, this was apparently recorded as a positive finding of an abnormality by two B-readers. These discrepancies were not reported by the ATSDR to study participants or by Peipins et al. (2003).

Perhaps the most troubling issue in the study by Peipins et al. (2003) is the misreading of plaques or thickening when only pleural fat was present. While acknowledging the confounding influence of obesity and pleural fat in determining pleural disease, Peipins et al. (2003) failed to scientifically account for this. The ATSDR (2001) reported that the body mass indexes (BMIs) of 67% of the 7,307 participants were [greater than or equal to] 25, indicating overweight, and 32% of these were obese (BMI of [greater than or equal to] 30). We independently verified the true incidence of overweight and obesity by calculating BMIs of the LMP participants: 89% were overweight and 54% were obese (Table 1).

Peipins et al. (2003) conceded that

   a heavier BMI can make it more difficult to distinguish
   between pleural abnormalities and subpleural
   or extraplural fat ...

This difficulty was clearly present in their study. As part of the HNA review, X rays and CT scans of study participants were sent for peer review as described above. Although this review is continuing, it is clear that in many cases, participants coded as positive for pleural changes either had no visible asbestos-related changes on their X rays or they had subpleural fat that was misdiagnosed as pleural thickening or plaques.

As a result of the study bias, nonconformity of the B-reader reports, and not accounting for high BMIs and pleural fat, the study by Peipins et al. (2003) markedly overstated the consequences of asbestos exposure in Libby, Montana.

The authors are employees of Health Network America, which is the plan administrator for the Libby Medical Plan. Medical evidence in support of applications is peer-reviewed by independent medical professionals to determine eligibility. Health Network America is paid a fee for its services that is independent of admission or nonadmission of applicants to the plan.

J. Jay Flynn

Stephen Kardos

Lin Yan

Health Network America, Inc.

West Eatontown, New Jersey

E-mail: [e-mail]

REFERENCES

ATSDR. 2001. Year 2000 Medical Testing of Individuals Potentially Exposed To Asbestoform Minerals Associated with Vermiculite in Libby, Montana A Report to the Community. Atlanta, GA:Agency for Toxic Substances and Disease Registry, Available: http://www.atsdr.edc.gov/ asbestos/doc_phl_testreport.html [accessed 12 January 2004].

Peipins LA, Lewin M, Campolucci S, Lybarger JA, Miller A, Middleton D, et al. 2003. Radiographic abnormalities and exposure to asbestos-contaminated vermiculite in the community of Libby, Montana, USA. Environ Health Perspect 111:1753-1759; doi:10.1289/ehp.0346 [Online 2 July 2003].