The Dynamics Of Tuberculosis In Response To 10 Years Of Intensive Control

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The Dynamics of Tuberculosis in Response to 10 Years of Intensive Control Effort in Peru
Pedro G. Suarez,1 Catherine J. Watt,2 Edith Alarcon,1 ´ ´ Jaime Portocarrero,1 David Zavala,1 Roberto Canales,1 Fabio Luelmo,2 Marcos A. Espinal,2 and Christopher Dye2
1

Ministerio de Salud, Enfermedades Transmisibles, Lima, Peru; 2 Communicable Diseases, World Health Organization, Geneva,Switzerland

Improved tuberculosis (TB) case detection and cure rates are expected to accelerate the decline in incidence of TB and to reduce TB-associated deaths. Time series analyses of case reports in Peru showed that the per capita TB incidence rate was probably steady before 1991. Case reports increased between 1990 and 1992 as a result of improved case detection. Although diagnostic efforts havecontinued to increase since 1993, the incidence of new pulmonary TB cases has declined in every department of the country, with a national rate of decline 5.8% per year (range, 1.9%–9.7%). This elevated rate of decline suggests that 27% (19%–34%) of cases (158,000) and 70% (63%–77%) of deaths (91,000) among smear-positive patients were averted between 1991 and 2000. This is the first demonstrationthat a significant number of TB cases can be prevented through intensive short-course chemotherapy in a high-burden country.

When tuberculosis (TB) control programs improve case detection and patient cure rates, we expect to see an accelerated decline in incidence and a reduction in the number of TB-related deaths. This expectation is based largely on theory [1] and on data from developedcountries [2]. There is scant evidence on what can be achieved in developing countries when control programs reach World Health Organization (WHO) targets of 70% case detection and 85% patient cure. Although 127 of 171 countries reporting to the WHO had adopted the DOTS (directly observed treatment, short-course) strategy for TB control by the end of 1999, only 7 were judged to have met the targets [3].Peru was among them. Peru has one of the highest TB incidence rates in the Americas (estimated as 228 per 100,000 population in 1999 [4]) and is one of 23 countries accounting for 80% of new TB cases worldwide each year. Three percent of the population of the Americas, but 15% of TB patients, live in Peru [3, 4]. The prevalence of human immunodeficiency virus (HIV) infection is low in Peru (0.56%in adults), especially when compared with high TB burden countries in Africa (adult prevalence, 4%–26% [5]). In August 1990, the National Tuberculosis Control Program (NTP) in Peru was revised, and the revised NTP (RNTP) follows the WHO DOTS strategy. A huge increase in case detection and diagnostic effort led first to an increase in reported

cases and then to a decline. Our principal goal inthis study was to learn what part of the drop in incidence over the past decade was attributable to the RNTP. The data underpinning our analysis are from routine reports of a national control program, not from a randomized controlled trial. Although data from national control programs lack the deductive power of a formal experiment, they have the twin compensations of countrywide coverage and ofproviding large quantities of information. The databases used in this study include 1 400,000 TB cases throughout Peru reported between 1991 and 2000, with treatment results for 1 200,000 patients. Our strategy was to compare the rate of decline in TB incidence before and after the intervention, making a conservative estimate of the difference between these two rates. To argue that this difference isattributable to the revised program, we relied on the timing of the fall in incidence, the consistency of the rate of decline with theory and with previous observation, and the absence of any alternative explanation. The estimate of the difference allowed us to evaluate the number of cases and deaths prevented by the RNTP since its introduction.

Methods
TB control program in Peru. The main...