Tuberculosis in Oriental Immigrants

We read with interest the article by Byrd et al’ concerning tuberculosis in Oriental immigrants. Although the authors correctly point out that immigrants from Asia do have higher rates of drug resistance than the indigenous US population, there are several statements in that article which we feel deserve comment and clarification. In the ongoing US Public Health Service primary drug resistance (PDR) study,2 21 percent of cases considered of Asian origin were found to be excreting organisms resistant to one or more of the ten drugs tested. However, not all these persons were immigrants, as implied by Byrd et al; an unknown proportion of our study participants of Asian heritage were American born. Therefore, our study data cannot be used to assess resistance rates among immigrants. As we stated in our article, the importation of drugresistant strains from other parts of the world is a likely explanation for the high PDR rates observed among persons of Hispanic or Asian backgrounds. However, in areas where large numbers of persons of Asian and Hispanic descent have settled, PDR rates are also high among white and black subjects. Although we can hypothesize that most drug resistance in these areas has been imported from other countries, our data do not prove that this is the case. Byrd and associates also imply that the state of Hawaii has partially solved the problem of imported drug resistance with a policy toward the admission of patients with tuberculosis which differs from that of the other 49 states. This is incorrect. Persons with “active” disease are not allowed to enter any state in the United States without special waiver. A more plausible reason for the lower resistance rate observed by Pien et al’ in Hawaii can probably be attributed to differences in criteria for drug resistance. Pien et al used the following drug concentrations (in g/ml) to determine resistance: streptomycin 10, isoniazid 1, ethambutol 8, and rifampin 5. By comparison the drug concentrations used by Byrd et al were much lower-streptomycin 2.5, isoniazid 0.1, ethambutol 5, and rifainpin 1. By using relatively high drug concentrations, Pien et al screened out strains with a low degree of drug resistance. On the other hand, Byrd et al, by using low concentrations, increased the likelihood of finding resistant strains. As Byrd and colleagues point out, their inability to obtain drug susceptibility test results for 40 patients who had become culture negative by the time they entered the hospital, tends to inflate the resistance rate among their patients. It is difficult to believe that “all dependents found to have tuberculosis while living overseas in their home country are referred” to Scott Air Force Base for evaluation. Since many patients with tuberculosis are managed as outpatients, we would wonder if there might not have been other patients with susceptible organisms who responded to treatment and were not sent to Scott Air Force Base. Although drug resistance is a problem among persons of Asian descent, the magnitude of the problem may not be as great as that implied by Byrd and coworkers. Preliminary data on drug resistance among Indochinese refugees in San Francisco indicate that drug resistance rates are between 15 and 20 percent (Austin Brewin, M.D., City and County of San Francisco Department of Public Health, personal com-