REPLY
Tuberculin Skin Tests in Hospital Employees
Thomas C. Bailey, MD;
Victoria J. Fraser, MD; and
William Claiborne Dunagan, MD
15 March 1996 | Volume 124 Issue 6 | Page 612
IN RESPONSE:
We thank Dr. Reichman for bringing his large study [1] to our attention. As in our study, Drs. Reichman and O'Day found independent statistical associations of race, indicators of socioeconomic status, and age with a positive tuberculin skin test result. Their study did not evaluate factors associated with incident tuberculous infection (skin test conversions). Although they do not describe the details of their multivariate analysis, they state that the association of a positive tuberculin skin test result with race was stronger than the association with current socioeconomic status. Interpretation of their results was complicated, however, by the likelihood that current socioeconomic status was better than it had been when tuberculous infection was probably acquired. Unfortunately, we do not have detailed data on previous residential postal zones of employees with positive skin test results to further investigate Dr. Reichman's hypothesis.
In addition to finding an association among the prevalence of positive tuberculin skin test results, race, and indicators of socioeconomic status, we found that skin test conversions were associated with race and socioeconomic indicators. The latter (as measured by the percentage of low-income persons within the employee's residential postal zone), however, was the only independent predictor of tuberculin skin test conversions. As Dr. Reichman notes, this finding is consistent with their previous speculation, because current socioeconomic status is more relevant to incident tuberculous infection. Because of the small number of skin test conversions in our study, however, we cannot exclude the possibility that, in a larger sample or in a different study population, an independent association of tuberculin skin test conversion with race might be seen.
As we discussed in our paper, and as Huth suggested in an unrelated editorial in the same issue [3], finding an epidemiologic association of self-reported race or ethnicity with any medical condition is a complex issue requiring careful interpretation. Dr. Reichman highlights one of many possible confounding factors that may lead to such associations.
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Author and Article Information
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Washington University Medical Center; St. Louis, MO 63110
1. Reichman LB, O'Day R. Tuberculous infection in a large urban population. Am Rev Respir Dis. 1978; 117:705-12.
2. Bailey TC, Fraser VJ, Spitznagel EL, Dunagan WC. Risk factors for a positive tuberculin skin test among employees of an urban, midwestern teaching hospital. Ann Intern Med. 1995; 122:580-5.
3. Huth EJ. Identifying ethnicity in medical papers [Editorial]. Ann Intern Med. 1995; 122:619-21.
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