WHO report 2008
Global tuberculosis control
1.6 Outcomes of treatment in DOTS programmes
1.6.1 New smear-positive cases
A total of 2 359 003 new smear-positive cases were registered for treatment in DOTS programmes in 2005, approximately the same number that were notified that year (Table 1.5). The biggest proportional discrepancies, where registered cases exceeded notifications, were in the Americas (Brazil), and in the Russian Federation and South Africa.
The cure rate among cases registered under DOTS worldwide was 77.6%, and a further 7.1% completed treatment (no laboratory confirmation of cure), giving a reported overall treatment success rate of 84.7%, very close to the 85% target (Table 1.5). This means that 49% of the smear-positive cases estimated to have occurred in 2005 were treated successfully by DOTS programmes. Among all the patients treated under DOTS, 9% had no reported outcome (defaulted, transferred, not evaluated). Treatment results for 12 consecutive cohorts (1994–2005) of new smear-positive patients show that the success rates have been 80% or higher in DOTS areas since 1998, even though the number of patients has increased 10-fold from 240 000 in 1994 to 2.4 million in 2005 (Table 1.5; Table 1.6).
The DOTS treatment success rate reached or exceeded 85% in ten HBCs (Table 1.5) and in 58 countries in total (Annex 3), and was reported to be 90% or more in cohorts of varying sizes in Afghanistan, Bangladesh, Cambodia, China, Indonesia and Viet Nam.
The global average treatment success rate was brought close to the target level by better outcomes in the South-East Asia and Western Pacific regions. The differences in treatment outcomes among WHO regions were similar to those reported in previous years, varying from 71% in Europe and 76% in Africa, to 87% in South-East Asia and 92% in the Western Pacific. The Western Pacific Region has always reported treatment success above the 85% target; South-East Asia has exceeded the target since 2002, and the Eastern Mediterranean Region has remained just below it (83% since 1999; Table 1.5, Table 1.6). Treatment success has been increasing in Africa, although cohorts of DOTS patients in this region continue to have high death and default rates: one or other of these indicators exceeded 10% in Mozambique, Nigeria, South Africa, Uganda and Zimbabwe.
In contrast to other regions, treatment outcomes deteriorated between 2004 and 2005 in the Region of the Americas and the European Region (Table 1.6). The treatment success rate of 71% in Europe in 2005 is the lowest recorded in that region since 1996 (albeit in an expanding cohort). In the Russian Federation, death and treatment failure rates were higher in 2005 than in any other HBC, and the treatment success rate of 58% was the lowest reported from that country since WHO records began in 1995. In the Region of the Americas in 2005, only 78% of patients completed treatment or were cured, the worst outcome since 1995.
Variation in treatment outcomes among regions raises important questions about the quality of treatment, the quality of the data and how quickly these will improve in future.
Poor outcomes in Africa and Europe are undoubtedly linked to high rates of HIV infection and drug resistance and to weak health services.1,2 Treatment results for individual African countries again point to the effects of HIV and inadequate patient support. The cohort death rate for the region as a whole was 7%, and higher still in Mozambique, Nigeria, South Africa, the United Republic of Tanzania and Zimbabwe (Table 1.5). Treatment interruption (default) and transfer without follow-up were also especially high in the African Region, at 8.6% and 4.5% respectively. More than 15% of patients had no known outcome in Ethiopia, South Africa, Uganda and Zimbabwe (Table 1.5). Cure was not confirmed (via a final, negative sputum smear) for large numbers of patients in Nigeria (25%) and Uganda (41%).
Death during treatment was 8.3% in the European Region, where a higher fraction of cases are drug resistant (Eastern Europe) or occur among the elderly (Western and Central Europe) (Figure 1.16). Treatment interruption was 7.7%, and the treatment failure rate was 8.4%, mainly because failure rates were high in Eastern Europe.
In the Region of the Americas, deteriorating outcomes are explained, at least in part, by the expansion of DOTS coverage, often into regions of countries with weaker health services. No outcome was reported for 16% of patients in the region as a whole (18% in Brazil) and in Brazil, 44% of patients completed treatment without cure being confirmed (via a final, negative sputum smear).
In 2005, as in previous years, treatment success was extraordinarily high in the Western Pacific Region (92%).
1.6.2 Re-treatment cases
A total of 531 232 patients were re-treated under DOTS in 2005 (Table 1.7). The re-treatment success rate in 2005 was 71%. As expected from the results of treating new patients, re-treatment success rates were lowest in the European Region (45%) and highest in the Western Pacific Region (87%).
1.6.3 Comparison of treatment outcomes in HIV-positive and HIV-negative TB patients
Data on the outcomes of treatment for HIV-positive and HIV-negative TB patients were reported separately by between 25 and 47 countries, depending on the category of case (Figure 1.17; smear-negative and extrapulmonary cases are presented as one category, since separate analysis showed very similar treatment outcomes for these two types of case). These countries were almost exclusively in the Region of the Americas and the European Region. There were few data for African countries (only Comoros, Gabon, and Mauritius), even though Africa accounts for 85% of estimated HIV-positive cases. The data that were reported show lower treatment success rates among HIV-positive patients, due mainly to higher death rates and, to a lesser extent, higher default rates. A similar pattern existed for two regions that could be analysed separately (the Region of the Americas and the European Region; data not shown).
1 As argued in Global tuberculosis control: surveillance, planning and financing. WHO report 2007. Geneva, World Health Organization, 2007 (WHO/HTM/TB/2007.376).
2 HIV may also have contributed to the high death rate in Thailand (12%) although, among Asian countries, Thailand has a relatively high proportion of elderly patients (Annex 3).