Risk factors for the development of non-response to first-line treatment for tuberculosis in southern Vietnam.

BACKGROUND: Acquired resistance to standard chemotherapy for tuberculosis (TB) is an increasing problem worldwide. Vietnam has one of the highest incidences of TB and also has a large population of potential migrants to other countries. Since 1979 the International Organisation for Migration (IOM) has been running a supervised programme of TB treatment for intending migrants from Vietnam where few facilities for bacteriological culture and sensitivity testing exist. This study aimed to assess the most important factors for predicting non-response to first-line treatment as treatment starts and whether any further indicators occur during the course of treatment which may enable more accurate prediction of non-response. METHODS: In all, 130 subjects failing to respond to first-line therapy (cases) between 1990 and 1995 were compared with 673 subjects who responded to therapy (controls) on various demographic and clinical characteristics using logistic regression to create a prognostic index. Variables analysed included the patient history of past TB treatment, weight, age, sex and radiological and bacteriological findings. All subjects also tested negative for HIV status. RESULTS: The chief markers of successful response were x-ray signs and degree of sputum smear positivity. These markers provided a prognostic index with an optimal cutoff providing about 70% sensitivity and 80% specificity. Incorporating further measures obtained through the first 3 months of treatment improved the sensitivity to 80%. CONCLUSION: While this study enabled prediction of the majority of subjects failing to respond to first-line therapy, other factors need to be assessed before recommendations for altering treatment regimens can be made. The prognostic index could be useful in assessing subjects for closer supervision.

PIP: Since 1979, the International Organization for Migration has provided tuberculosis screening and treatment for those who intend to migrate from Viet Nam--a country with one of the highest tuberculosis incidence rates. The factors associated with non-response to first-line tuberculosis treatment were investigated in a comparative study of 130 non-responders (cases) and 673 responders (controls). Cases had worse radiologic signs and greater numbers of acid-fast bacilli on their sputum smears than controls. When these two factors were used as a diagnostic test to predict non-response, the model had a sensitivity of 70% and a specificity of 80%. Sensitivity increased to 80% when variables measured in the first 3 months of treatment were used. Failure to respond to treatment can be a result of infection with other mycobacteria, infection with a multi-drug resistant tuberculosis strain, or acquisition of resistance after the initiation of therapy. Further analysis of the same database is underway to determine the natural history and success of second-line treatment.

Prevalence of tuberculosis in Vietnamese migrants: the experience of the Orderly Departure Program.

This study aimed to describe the Internal Organization for Migration (IOM) tuberculosis screening and treatment program in Ho-Chi-Minh City (Vietnam); and to review the prevalence of tuberculosis and treatment outcome in a cohort of Vietnamese migrants and refugees prior to their departure. From 1 November 1992 to 1 June 1993, prospective migrants and refugees bound to the United States, Australia, and Canada underwent medical examination by IOM in Ho-Chi-Minh City. Screening for tuberculosis was based on chest x-rays, and the diagnosis was confirmed by smear examination. Smear-positive patients received short-course chemotherapy, directly supervised, with isoniazid, rifampicin, ethambutol, and pyrazinamide. Out of 39,581 persons screened, 322 were smear-positive (641 per 100,000), and started treatment. Follow-up varied from a minimum of 12 months to a maximum of 18 months. At that time, 265 (82%) were cured, while the remaining either continued treatment with first-line drugs (24), started second-line treatment (17), or failed to be cured for various reasons (16). This report confirms the efficacy of short course chemotherapy and directly observed treatment for tuberculosis, in the context of one of the largest screening programs for prospective migrants. Follow-up in receiving countries would help clarify risk factors for both new infection and relapse of tuberculosis.