Document nJQK1m6yJVj5b48mg02d7m4G

American Journal of Industrial Medicine 24051-256 (1993) LETTER TO THE EDITOR Diagnostic Bias in Occupational Epidemiologic Studies: An Example Based on the Vinyl Chloride Literature Key words: vinyl chloride, brain cancer, emphysema, chronic obstructive pulmonary disease, diagnostic bias INTRODUCTION Dr. Shah's Letter [1993] raised several issues of potential diagnostic bias on the brain cancer and emphysema findings in our recent paper of vinyl chloride workers [Wong et al., 1991]. These are important and pertinent questions not only in our study of vinyl chloride exposed workers, but also in occupational epidemiologic studies in general. BRAIN CANCER The first issue was the potential diagnostic bias of brain cancer in occupational studies. As Dr. Shah correctly pointed out in his letter, there are reports in the literature documenting the potential bias resulting from the more complete repotting and/or diagnoses of brain tumors in employees of large corporations than in the general population. Greenwald et al. [1981] reported a significantly higher frequency of brain scans (61.1% vs. 30.0%) and pneumoencephalograms (35.2% vs. 17.1%) than in other brain tumor patients in the same state. They concluded that the "diag nostic sensitivity bias" would appear to pertain to conditions that are difficult to diagnose, such as brain tumors, and to industries where workers have such employee benefits as health insurance and high-quality employee medical services with referral and follow-up. Thus, the apparent excess of brain tumors may have resulted from the diagnostic sensitivity bias arising from the more complete medical evaluation of employees of large corporations. Diagnostic sensitivity bias in brain cancer has also been discussed by other investigators [Wong et al., 1986; Wong and Raabe, 1989]. The participants in our vinyl chloride study were employees of major corpora tions in the chemical industry, and were covered by comprehensive medical care Address reprint requests to Dr. O. Wong, Applied Health Sciences, Inc., 181 Second Avenue, Suite 628, P.O. Box 2078, San Mateo, CA 94401. Accepted for publication December 12, 1992. 1993 Wiley-Liss, Inc. T(j 08S8Z