Global Tuberculosis Report -- 2012.pdf

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This annex explains the methods that were used to produceestimates of the global burden of disease caused byTB (measured in terms of incidence, prevalence and mortality).It has nine major sections:● General approach. This section provides some backgroundinformation about the methods used to produceestimates of disease burden.● Definitions. This section defines TB incidence, prevalenceand mortality, the case fatality rate (CFR) andthe case notification rate. It also explains the regionsfor which estimates of disease burden are producedand sources of information on population estimates.● Estimates of TB mortality, 1990–2011. This sectionexplains the three methods used to estimate TB mortality,and the countries for which they were applied.Methods for estimating the number of HIV-associatedTB deaths and for disaggregation of TB mortality byage and sex are also described.● Estimates of TB incidence, 1990–2011. This sectionexplains the main methods used to estimate TB incidence,and the countries for which they were applied.Methods to estimate the prevalence of HIV amongincident TB cases are described.● Estimates of TB prevalence, 1990–2011. This sectionexplains the two methods used to estimate TBprevalence, and the countries for which they wereapplied.● Estimates of the number of cases of multidrugresistantTB (MDR-TB). This section explains howestimates of the proportion of notified cases of TB thathad MDR-TB in 2011 were produced and used to assessthe number of prevalent cases of MDR-TB in 2011.● Projections of TB incidence, prevalence and mortality.This section explains how projections up to2015 were produced.● Uncertainty framework. This section explains thegeneral approach to including uncertainty in all estimates.1. General approachEstimates of the burden of disease caused by TB (measuredin terms of incidence, prevalence and mortality)are produced annually by WHO using information gatheredthrough surveillance systems (case notifications anddeath registrations), special studies (including surveys ofthe prevalence of disease, mortality surveys and in-depthanalyses of surveillance data), expert opinion and consultationswith countries. Two recent publications provideup-to-date guidance about how TB incidence, prevalenceand mortality should be measured, 1 based on the workof the WHO <strong>Global</strong> Task Force on TB Impact Measurement.2 The methods used to estimate the burden of diseasewere updated in 2009 following 18 months of workby an expert group convened by the Task Force. Improvementsto methods included systematic documentation ofexpert opinion and how this has been used to produceestimates of disease burden, simplification of models, 3updates to parameter values based on the results of systematicreviews, much greater use of mortality data fromVR systems and systematic documentation of uncertainty(hence the uncertainty intervals shown on all of the estimatesof disease burden in this report).2. Definitions2.1 Incidence, prevalence, mortality, case fatalityrate, case notification rateIncidence is defined as the number of new and recurrent(relapse) episodes of TB (all forms) occurring in a givenyear. Recurrent episodes are defined as a new episode ofTB in people who have had TB in the past and for whomthere was bacteriological confirmation of cure and/ordocumentation that treatment was completed (Box 3.1,Chapter 3). In the remainder of this Annex, relapse casesare referred to as recurrent cases because the term is moreuseful when explaining the estimation of TB incidence.Recurrent cases may be true relapses or a new episodeof TB caused by reinfection. In current case definitions,both relapse cases and patients who require a change intreatment are called “retreatment cases”. However, peoplewith a continuing episode of TB that requires a treatmentchange are prevalent cases, not incident cases.Prevalence is defined as the number of TB cases (allforms) at a given point in time.Mortality from TB is defined as the number of deathscaused by TB in HIV-negative people, according to the latestrevision of the international classification of diseases(ICD-10). TB deaths among HIV-positive people are classifiedas HIV deaths in ICD-10. For this reason, estimatesof deaths from TB in HIV-positive people are presentedseparately from those in HIV-negative people.The case fatality rate is the risk of death from TB amongpeople with active TB disease. 4The case notification rate refers to new and recurrentepisodes of TB notified to WHO for a given year, expressedper 100 000 population. The case notification rate for newand recurrent TB is important in the estimation of TB1TB impact measurement: policy and recommendations for how toassess the epidemiological burden of TB and the impact of TB control.Geneva, World Health Organization, 2009 (Stop TB policypaper, no. 2; WHO/HTM/TB/2009.416). The policy paper isavailable on the Task Force’s web sitewww.who.int/tb/advisory_bodies/impact_measurement_taskforce2For further details, see the Task Force web site at:www.who.int/tb/advisory_bodies/impact_measurement_taskforce3For example, some parameter values are now estimated onlyat global level or for regions, rather than for each country individually.4Straetemans M et al. Assessing tuberculosis case fatality ratio:a meta-analysis. PLoS One. 2011, 6(6):e20755.GLOBAL TUBERCULOSIS REPORT 2012 93
incidence. In some countries, however, information ontreatment history may be missing for some cases. Whendata on treatment history are not available, recurrentcases cannot be distinguished from cases whose treatmentwas changed, since both are registered and reportedin the category “retreatment”. Data for patients reportedin the “unknown history” category are assessed withnational TB control programmes (NTPs) to determine theproportion of such patients included in the category ofrecurrent cases.2.2 RegionsRegional analyses are generally undertaken for the sixWHO regions (that is, the African Region, the Regionof the Americas, the Eastern Mediterranean Region, theEuropean Region, the South-East Asia Region and theWestern Pacific Region). For analyses related to MDR-TBand for an ecological model used to estimate TB mortalityin some countries, nine epidemiological regions weredefined. These were African countries with high HIVprevalence, African countries with low HIV prevalence,Central Europe, Eastern Europe, high-income countries,1 Latin America, the Eastern Mediterranean Region(excluding high-income countries), the South-East AsiaRegion (excluding high-income countries) and the WesternPacific Region (excluding high-income countries). Thecountries in these nine regions are listed in Appendix 1.2.3 Population estimatesWhere population sizes are needed to calculate TB indicators,the 2012 revision of estimates provided by theUnited Nations Population Division (UNPD) was used. 2The UNPD estimates sometimes differ from those madeby countries.3. Estimates of TB mortality, 1990–2011The best sources of data about deaths from TB (excludingTB deaths among HIV-positive people) are VR systemsin which causes of death are coded according to ICD-10(although the older ICD-9 and ICD-8 classification arestill in use in several countries). Deaths from TB in HIVpositivepeople are coded under HIV-associated codes.Three methods were used to estimate TB mortality:● direct measurements of mortality from vital registration(VR) systems or mortality surveys.● indirect estimates based on an ecological model.● indirect estimates derived from multiplying estimatesof TB incidence by estimates of the CFR.Each method is described in more detail below. The sourceof data used for each country is available from tbdata@who.int upon request.3.1 Estimating TB mortality from vital registrationdata and mortality surveysData from VR systems are reported to WHO by MemberStates and territories every year. In countries with functioningVR systems in which causes of death are codedaccording to the two latest revisions of the internationalclassification of diseases (underlying cause of death:ICD-10 A15-A19, equivalent to ICD-9: 010-018), VR dataare the best source of information about deaths from TBamong people not infected with HIV. When people withAIDS die from TB, HIV is registered as the underlyingcause of death and TB is recorded as a contributory cause.Since one third of countries with VR systems report toWHO only the underlying causes of death and not contributorycauses, VR data usually cannot be used to estimatethe number of TB deaths in HIV-positive people.TB mortality data obtained from VR systems are essentialto understanding trends in TB disease burden wherecase notifications have incomplete coverage or their coverageis not documented through an inventory study. Anupdated description of the global coverage and quality ofVR data is available in World Health Statistics 2012. 3As of May 2012, 122 countries had reported mortalitydata to WHO (including data from sample VR systemsand mortality surveys), among 217 countries and territoriesfrom which TB data were requested. These 122countries included 8 of the 22 high TB-burden countries(HBCs): Brazil, China, India, the Philippines, the RussianFederation, Thailand, South Africa and Zimbabwe.However, the VR data on TB deaths from South Africaand Zimbabwe were not used for this report because largenumbers of HIV deaths were miscoded as TB deaths.Improved empirical adjustment procedures have recentlybeen published, 4 and specific post-hoc adjustments formisclassification errors in the measurement of TB mortalitywill be attempted before preparing the 2013 WHOreport on global TB care and control.Among the countries for which VR data could be used(see Figure 2.11 in Chapter 2), there were 1928 countryyeardata points 1990–2011. Of these data points, 30outliers and points obtained from systems with very lowcoverage were excluded for analytical purposes. Outlierswere detected visually by plotting country-specific timeseries of reported TB mortality rates. As of May 2012,only 29 data points were available for 2010 and none for1High-income countries are defined by the World Bank ascountries with a per capita gross national income (GNI) ofUS$ 12 475 in 2011.2http://esa.un.org/unpd/wpp/unpp/panel_population.htm; accessed May 2012.3www.who.int/gho/publications/world_health_statistics/2012/en/; accessed July 2012 (see particularlypages 44–45).4Birnbaum JK, Murray CJL, Lozano R. Exposing misclassifiedHIV/AIDS deaths in South Africa. Bulletin of the World HealthOrganization, 2011, 89:278–285.94 GLOBAL TUBERCULOSIS REPORT 2012
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GLOBALTUBERCULOSISREPORT2012
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ContentsAbbreviationsivAcknowledgem
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AcknowledgementsThis report on glob
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WHO Western Pacific RegionShalala A
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Executive SummaryThe World Health O
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CHAPTER 1IntroductionBOX 1.1Basic f
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TABLE 1.1 Targets for the scale-up
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TABLE 1.2 Reporting of data in the
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BOX 2.1Uncertainty in estimates of
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TABLE 2.2 Estimated burden of disea
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FIGURE 2.5 Estimated TB incidence r
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FIGURE B2.2.1Reporting of notificat
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FIGURE 2.8Estimated TB incidence ra
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FIGURE 2.11 Countries (in blue) for
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FIGURE 2.12 Trends in estimated TB
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● producing and widely disseminat
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FIGURE 2.16 Progress in global cove
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BOX 2.6Efforts by the Task Force to
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CHAPTER 3TB case notificationsand t
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BOX 3.1 1Definitions of TB casesDef
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TABLE 3.3 Contribution of public-pr
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BOX 3.4Integrating community-based
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TABLE 3.4 Estimates of the case det
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TABLE 3.5 Treatment success for new
Page 50 and 51: CHAPTER 4Drug-resistant TBKEY FACTS
Page 52 and 53: FIGURE 4.2 Percentage of new TB cas
Page 54 and 55: BOX 4.1Frequencies of resistance to
Page 56 and 57: FIGURE 4.6 Number of MDR-TB cases e
Page 58 and 59: FIGURE 4.7Notified cases of MDR-TB
Page 60 and 61: egimens globally, providing more su
Page 62 and 63: 5.1 Funding for TB care and control
Page 64 and 65: TABLE 5.2 NTP budgets, available fu
Page 66 and 67: FIGURE 5.5Trends in domestic and do
Page 68 and 69: FIGURE 5.6Domestic funding as a per
Page 70 and 71: FIGURE 5.8Cost per TB patient succe
Page 72 and 73: FIGURE 5.10 Total cost and unit cos
Page 74 and 75: ● The 14 countries not included i
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Page 78 and 79: evised as a result of the introduct
Page 80 and 81: TABLE 6.2 Incorporation of WHO poli
Page 82 and 83: FIGURE 6.3The Supranational Referen
Page 84 and 85: of TB disease by 65%, irrespective
Page 86 and 87: FIGURE 7.3Percentage of TB patients
Page 88 and 89: BOX 7.1Accelerating progress in pro
Page 90 and 91: TABLE 7.2 Assumptions used to estim
Page 92 and 93: FIGURE 8.1 The development pipeline
Page 94 and 95: sputum specimens and TB isolates fr
Page 96 and 97: cal trial sites and building labora
Page 98: new TB vaccine candidate. A Phase I
Page 104 and 105: 2011. On average, 15 data points we
Page 106 and 107: may suffer from biases. These biase
Page 108 and 109: TABLE A1.3Parameter estimates used
Page 110 and 111: 5. Estimates of TB prevalence, 1990
Page 112: the Republic of Moldova, Romania, t
Page 116 and 117: AFGHANISTANPopulation 2011 32 milli
Page 118 and 119: BRAZILPopulation 2011 197 millionHI
Page 120 and 121: CHINAPopulation 2011 1 348 millionH
Page 122 and 123: ETHIOPIAPopulation 2011 85 millionH
Page 124 and 125: INDONESIAPopulation 2011 242 millio
Page 126 and 127: MOZAMBIQUEPopulation 2011 24 millio
Page 128 and 129: NIGERIAPopulation 2011 162 millionH
Page 130 and 131: PHILIPPINESPopulation 2011 95 milli
Page 132 and 133: SOUTH AFRICAPopulation 2011 50 mill
Page 134 and 135: UGANDAPopulation 2011 35 millionHIG
Page 136 and 137: VIET NAMPopulation 2011 89 millionH
Page 138: ANNEX 3Regional profiles
Page 141 and 142: WHO REGION OF THE AMERICASPopulatio
Page 143 and 144: WHO EUROPEAN REGIONPopulation 2011
Page 145 and 146: WHO WESTERN PACIFIC REGIONPopulatio
Page 148 and 149: SUMMARY BY WHO REGIONTable A4.1 Est
Page 150 and 151: MORTALITY (EXCLUDING HIV) PREVALENC
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NEW AND RELAPSENOTIFICATION RATE aY
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-% OF TB PATIENTS WITHKNOWN HIV STA
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AFRICAN REGIONTable A4.1 Estimates
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MORTALITY (EXCLUDING HIV) PREVALENC
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INCIDENCE (INCLUDING HIV) INCIDENCE
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NEW AND RELAPSENOTIFICATION RATE aY
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NEW AND RELAPSENOTIFICATION RATE a1
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TREATMENT SUCCESS (%) a1995-2010YEA
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YEARTOTALCONFIRMEDCASES OFMDR-TB aE
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MALEYEAR 0-14 15-24 25-34 35-44 45-
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REGION OF THE AMERICASTable A4.1 Es
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% OF COHORTTREATMENT SUCCESS (%) a1
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MALEFEMALEYEAR 0-14 15-24 25-34 35-
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EASTERN MEDITERRANEAN REGIONTable A
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EUROPEAN REGIONTable A4.1 Estimates
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SOUTH-EAST ASIA REGIONTable A4.1 Es
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SMEAR LABS % OF SMEARPER 100K LABS
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Estimates of mortality, prevalence
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YEARPOPULATION(MILLIONS)MORTALITY (
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YEARPOPULATION(MILLIONS)INCIDENCE (
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YEARPOPULATION(MILLIONS)INCIDENCE (
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SMEAR LABS % OF SMEARPER 100K LABS
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