Multidrug-resistant tuberculosis(MDR-TB) in patients is mainly caused by acquired drug resistance, However, a small proportion of MDR-TB is caused by initial drug resistance(IDR), which may be somewhat different from acquired drug resistance. This study analyzed the clinical characteristics of IDR in MDR-TB patients to use the results as basic data in managing the disease.

A retrospective study of 30 IDR cases in MDR-TB patients from Jan. 1995 to Dec. 1998 was perormed. In order to analyzed the clinical charcteristics, the age, sex, family history, duration of negative conversion, number of resistant drugs, treatment regimens, duration of treatment, extent of disease and cavitary lesion on the chest X-ray was examined. In order too analyzed the level of improvement, the extent of the disease and cavitary lesion on the chest X-ray, tested by Wilcoxon signed rank sum test, and the disease free interval rate of 1-year and 4-year was examined using the Kaplan-Meier method.

The mean age of the patients was 46.6 years and the sex ratio 1:1. Six(20%) patients had a family history. The mean negative conversin of the sputum AFB stain was 2.6 months. The number of resistant drugs was 7.6 and the number of used drugs 3.6. Twenty-three(67%) patients were treated for less than 12months and 28(93%) patients were treated with first-line drugs. The extent of the disease and the cavitary lesion on the chest X-ray improved after treatment(p<0.05). Among 13 patients who were followed up for 22.6 months, 2(15%) patients relapsed and the disease free interval rate of 1-year and 4-year was 85%.

It is recommended that the duration of treatment of IDR in MDR-TB with first-line drugs be 9-12 months even if the extent of disease and cavitary lesion on the chest X-ray improves.