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TB Notes 2, 2004


Evaluation of the Brazilian National TB Surveillance System

Most epidemiologists, public health policy makers, TB program managers, and health experts would agree that TB surveillance is a crucial tool in their decision making. Where disagreement may arise among the various stakeholders is in their assessment of the system’s reliability, completeness of coverage, and utility, among other attributes. For example, in Brazil, the national TB surveillance system (SINAN-TB: Sistema de Informação de Agravos de Notificação-Tuberculose) reported to the World Health Organization (WHO) approximately 74,500 new TB cases in 2001, whereas WHO’s own estimate of TB cases in Brazil for that year was approximately 110,500 — a substantial difference (WHO estimates total TB cases based on TB incidence reappraisals in reporting countries).1,2 In recognition of the importance of accurate surveillance data, the Brazilian Ministry of Health invited the International Research and Programs Branch (IRPB) of DBTE to participate in an evaluation of SINAN-TB.

In order to accomplish the evaluation of the Brazilian TB surveillance system information was gathered from six different sources: (1) SINAN-TB; (2) Livro Preto (the local TB registries kept at each treatment facility; (3) patient records; (4) Sistema de Informação de Mortalidade (SIM), a national mortality reporting system; (5) interviews with treatment center staff; and (6) interviews with municipal, regional, state, and federal TB program administrators. A comparison of specific data elements between SINAN-TB and Livro Preto (and patient records), and between SINAN-TB and SIM was designed to assess the more quantitative aspects of SINAN-TB including data quality, completeness of coverage, representativeness, and timeliness. The qualitative assessment of the system relied on personnel interviews to determine the system’s simplicity, flexibility, acceptability, stability and utility.

Relatively new to the world of TB surveillance is the capture-recapture methodology,3 used in this evaluation to estimate SINAN-TB completeness of coverage. This strategy, first applied in wildlife management, estimates the number of uncounted TB patients by matching the number of patients simultaneously recorded by two or more surveillance systems that capture parallel information (i.e., number of TB deaths in SIM matched against the number of TB patients in SINAN whose outcome is death). A two-source model can estimate a system’s completeness of coverage fairly accurately if the underlying assumptions of the capture-recapture method are not violated: (1) cases must have the same probability of appearing in each source, (2) the probability of a case appearing in any source is independent of the other sources, and (3) the population under study is closed.3

Data on approximately 1000 TB patients listed in the year 2000 in the Livro Preto, encompassing approximately 15 treatment centers in 4 Brazilian cities (Rio de Janeiro, Maceio, Porto Alegre, and Recife) were matched to those of patients from the same geographical areas and treatment time period as recorded in SINAN-TB. Approximately 100 total TB staff members from these treatment centers and from TB programs at various governmental levels were interviewed. In addition, records of patients who died in 2000 or 2001 with a TB diagnosis (by ICD-9 coding of the primary-, secondary-, tertiary-, and quaternary-associated diagnoses) as recorded in SIM were matched with those of patients recorded in SINAN-TB for the year 2000 from the four cities surveyed--over 15,000 names. 

The overall evaluation found SINAN data quality to be good with one exception: follow-up patient information. For example, 80% of follow-up sputum smears and 64% of patient outcomes were missing from SINAN-TB. Further, almost one fourth of staff members interviewed did not feel they were an important part of the system,  suggesting, along with responses to other questions, that SINAN-TB acceptability was low. Timeliness of the system was also suboptimal, mainly because the end users received epidemiologic data feed-back unevenly and infrequently. Consequently the utility of SINAN-TB was felt to be limited.

Conflicting results were obtained for SINAN-TB completeness of coverage.  When compared to Livro Preto, the system’s coverage was estimated to be about 71%, a figure much closer to WHO estimates of TB case detection in Brazil in 2000. When compared to SIM, however, the estimate of the system’s coverage fell to 24%. One possible explanation for this latter difference is that deaths in SIM may have occurred or been reported in jurisdictions other than the municipality where patients were receiving TB treatment, or vice versa, thus violating the “closed population” assumption of capture-recapture methodology. This situation may falsely lower the estimated completeness of coverage of SINAN-TB (and of SIM as well). In order to test this hypothesis, the matching of TB patients in SIM and SINAN-TB is being expanded to include the four states in which the four surveyed cities are located. Tuberculosis patients in the SIM and SINAN-TB databases for each state, in its entirety, will be matched.  The goal of this approach is to minimize geographical reporting artifacts. In addition, log linear modeling will be applied to the three databases used for this evaluation in order to arrive at a more accurate completeness of coverage figure for SINAN-TB.

In conclusion, this evaluation found SINAN-TB to be a useful TB surveillance system; however, its utility is reduced by (1) low capture of follow-up TB patient information, thus hindering program evaluation at all levels; (2) deficient data feedback, limiting program improvement efforts at local and regional levels; and (3) relatively low completeness of coverage (range 24%-71%), possibly leading to underreporting of TB cases.

The following recommendations were made to the Brazilian Ministry of Health, Secretariat for Health Policy. The Brazilian National TB Program should consider the following: (1) establishing a federal SINAN-TB advisory council to assess, develop, and oversee system changes and serve as a representative body to address end-user interests and needs; (2) establishing accountable executive positions with budgetary and oversight authority as well as with responsibility at the state and municipal levels for the purposes of quality assurance; and (3) ensuring access to and feedback of epidemiologic TB information for all programmatic administrative levels, as well as encouraging the use this information through currently available resources (i.e., technology, training, technical assistance).

As of this writing, a number of the recommendations made by the International Research and Programs Branch (IRPB) of DTBE for the improvement of SINAN-TB have been implemented, as modified by prevailing circumstances. The impact of the applied recommendations has not yet been assessed; however, the evaluation has been instrumental in raising the completeness of patient follow-up information in SINAN-TB from approximately 30% to 50%. In addition, with a credible assessment of Brazil’s TB surveillance system available to them, public health officials now take into consideration SINAN-TB underreporting of TB cases in programmatic and policy decisions while the system is improved.

—Reported by Abe Miranda, MD
Div of TB Elimination


1. WHO Report 2003. Global Tuberculosis Control. Surveillance, Planning, and Financing. Geneva.

2. Corbett EL et al. The growing burden of tuberculosis: global trends and interactions with the HIV epidemic. Arch Int Med 2003; 163: 1009-21.

3. Hook EB, Regal RR. Capture-recapture methods in epidemiology: methods and limitations. Epidemiol Rev 1995; 17: 243-264.


Released October 2008
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