3.2 Diagnostic testing for TB, HIV-associated TB and drug-resistant TB

Fig. 3.2.1 Percentage of people newly diagnosed with pulmonary TB who were bacteriologically confirmed, globally and for WHO regions,^a 2000–2021

There is considerable country variation (Fig. 3.2.2) in the proportion of people diagnosed with a new episode of pulmonary TB who were bacteriologically confirmed in 2021.

Fig. 3.2.2 Percentage of people newly diagnosed with pulmonary TB who were bacteriologically confirmed at country level, 2021

In general, levels of confirmation are lowest in low-income countries and highest in high-income countries (Fig. 3.2.3), where there is wide access to the most sensitive diagnostic tests. Over-reliance on direct sputum smear microscopy is inherently associated with a relatively high proportion of pulmonary TB cases that are clinically diagnosed, as opposed to bacteriologically confirmed.

Fig. 3.2.3 The proportion of people newly diagnosed with pulmonary TB who were bacteriologically confirmed in 2021, by country income group

In the 30 high TB burden countries (Fig. 3.2.4), variation in the proportion of people diagnosed with pulmonary TB who were bacteriologically confirmed likely reflects differences in diagnostic and reporting practices. Countries with relatively high levels of bacteriological confirmation (around 75%) include Bangladesh, Brazil, the Democratic Republic of the Congo, Liberia, Mongolia, Namibia, Nigeria and Viet Nam. There is clear scope for improvement in most other countries; this is particularly needed in countries such as Mozambique and Philippines, where worrying declines have been reported in recent years. These declines show overdependence on clinical diagnosis of TB and potentially over-diagnosis. When the proportion of people diagnosed with pulmonary TB based on bacteriological confirmation falls below 50%, a review of the diagnostic tests in use and the validity of clinical diagnoses is warranted (e.g. via a clinical audit).

Fig. 3.2.4 Percentage of people newly diagnosed with pulmonary TB who were bacteriologically confirmed, 30 high TB burden countries, 2000–2021

Globally in 2021, a WHO-recommended rapid diagnostic test was used as the initial diagnostic test for 2.5 million (38%) of the 6.4 million people newly diagnosed with TB in 2021. This was an improvement from 33% in 2020 and 28% in 2019. There was substantial variation among countries (Fig. 3.2.5). Among the 30 high TB burden countries, those with very high proportions (above 90%) included Namibia, Viet Nam and Zambia. Among the 49 countries in one of the three global lists of high burden countries (for TB, HIV-associated TB and MDR/RR-TB) being used by WHO in the period 2021–2025 (see Annex 3 of the main report), 26 reported that a WHO-recommended rapid diagnostic test had been used as the initial test for more than half of their notified TB cases in 2021, up from 21 in 2020 and 18 in 2019.

Fig. 3.2.5 Percentage of people newly diagnosed with TB who were initially tested with a WHO-recommended rapid test at country level, 2021

In 2021, the proportion of TB diagnostic sites with access to WHO-recommended rapid diagnostic tests varied considerably by country (Fig. 3.2.6). Globally, the median was at 25% (Interquartile range (IQR): 11–63%). Only 7 of the 30 high TB burden countries reported that more than 50% of their TB diagnostic sites had access to WHO-recommended rapid diagnostic tests.

Fig. 3.2.6 Proportion of diagnostic sites for TB with access to WHO-recommended rapid tests at country level, 2021

The number of WHO-recommended rapid TB diagnostic tests used per capita also provides an indication of the reach of rapid testing. There is substantial variation among the 30 high TB burden countries (Fig. 3.2.7). The five countries that exceeded 1000 tests per 100 000 population were all in the African Region: Lesotho, Mozambique, Namibia, South Africa and Zambia.

Fig. 3.2.7 Number of WHO-recommended rapid tests used per 100 000 population, 30 high TB burden countries, WHO regions and globally, 2021

The percentage of people initially tested with a WHO-recommended rapid test who had a positive test result provides an indication of the level of case-finding efforts (Fig. 3.2.8). A low percentage suggests a lack of precision in deciding who to test, while a high percentage suggests suboptimal efforts to detect people with TB. In 2021, there was considerable variation among the 30 high TB burden countries and WHO regions.

Fig. 3.2.8 Percentage of people initially tested for TB with a WHO-recommended rapid test who had a positive test result, 30 high TB burden countries, WHO regions and globally,^a 2021

The number of WHO-recommended rapid tests used per person notified as a TB case also provides an indication of the level of diagnostic effort based on rapid tests. In 2021, the number of rapid tests per notified case varied widely in the 30 high TB burden countries, from under 2 in 14 countries to a high of 12 in South Africa (Fig. 3.2.9).

Fig. 3.2.9 Number of WHO-recommended rapid diagnostic tests per person notified as a TB case (new and relapse cases, all forms), 30 high TB burden countries, 2021

Of the 6.4 million people newly diagnosed with TB globally in 2021, 76% had a documented HIV test result, up from 73% in 2020 (Fig. 3.2.10). At regional level, the highest percentages were achieved in the WHO African and European regions.

Fig. 3.2.10 Percentage of new and relapse TB cases^a with documented HIV status, globally and for WHO regions^b, 2004–2021

There was considerable variation at national level (Fig. 3.2.11). In 119 countries and territories, at least 90% of people diagnosed with TB knew their HIV status. In most countries, the percentage was above 50%, but in a small number of countries it is still the case that fewer than half of the people diagnosed with TB know their HIV status.

Fig. 3.2.11 Percentage of people newly diagnosed with TB whose HIV status was documented at country level, 2021

Worldwide, a total of 368 641 cases of TB among people living with HIV were notified in 2021 (Table 3.1.1), equivalent to 7.7% of the 4.8 million people diagnosed with TB who had an HIV test result. Overall, the percentage of people diagnosed with TB who had an HIV-positive test result has fallen globally over the past 10 years.

Bacteriological confirmation of TB is necessary to test for drug-resistant TB. In 2021, 70% of people with bacteriologically confirmed TB were tested for resistance to rifampicin (the most effective first-line anti-TB drug), a slight decline from 71% in 2020 (Fig. 3.2.12). There were declines in the WHO South-East Asia and Western Pacific regions, which contrasted with improvements in the WHO regions of Africa, the Americas and the Eastern Mediterranean.

Fig. 3.2.12 Percentage of people diagnosed with bacteriologically confirmed TB who were tested for rifampicin-resistant TB (RR-TB^a), globally and for WHO regions, 2009–2021

There was considerable variation in the coverage of testing for rifampicin-resistant TB (RR-TB) among countries (Fig. 3.2.13). There are 30 countries (see Annex 3 of the main report PDF) that WHO has defined as high burden for multidrug-resistant/RR-TB (MDR/RR-TB; MDR-TB is defined as resistance to both rifampicin and isoniazid). Of these, 20 reached coverage of testing for RR-TB of more than 80% in 2021: Azerbaijan, Belarus, China, Kazakhstan, Kyrgyzstan, Mongolia, Mozambique, Myanmar, Pakistan, Peru, the Philippines, the Republic of Moldova, the Russian Federation, South Africa, Tajikistan, Ukraine, Uzbekistan, Viet Nam, Zambia and Zimbabwe.

Fig. 3.2.13 Percentage of people diagnosed with bacteriologically confirmed TB who were tested for rifampicin-resistant TB (RR-TB^a) at country level, 2021

Among people tested for RR-TB, a total of 141 953 cases of MDR/RR-TB and 25 038 cases of pre-XDR-TB or XDR-TB were detected (Table 3.1.1), for a combined total of 166 991. This was a small increase (6.4%) from a combined total of 156 982 in 2020, and smaller than the 10% increase in the number of people diagnosed and reported with TB between 2020 and 2021 (Section 3.1).

The global and regional coverage of testing for susceptibility to fluoroquinolones, which is necessary to determine the most appropriate treatment regimen for people with RR-TB, is lower than the coverage of testing for RR-TB (Fig. 3.2.14). The highest coverage in 2021 was in the WHO European Region.

Fig. 3.2.14 Percentage of people diagnosed with rifampicin-resistant TB (RR-TB) who were tested for susceptibility to fluoroquinolones^a, globally and for WHO regions, 2015–2021

There is considerable country variation in the proportion of people diagnosed with RR-TB who were tested for susceptibility to fluoroquinolones (Fig. 3.2.15).

Fig. 3.2.15 Percentage of people diagnosed with rifampicin-resistant TB (RR-TB) who were tested for susceptibility to fluoroquinolones at country level, 2021

Bedaquiline is recommended by WHO as part of treatment regimens for people with MDR/RR-TB and pre-extensively-resistant TB (pre-XDR-TB). Since 2021, pre-XDR-TB is defined as MDR/RR-TB plus resistance to any fluoroquinolone. The percentage of people with pre-XDR-TB tested for susceptibility to bedaquiline remains low in most parts of the world (Fig. 3.2.16).

Fig. 3.2.16 Percentage of people diagnosed with pre-XDR-TB^a who were tested for susceptibility to bedaquiline at country level, 2021

Linezolid is also recommended by WHO as part of treatment regimens for MDR/RR-TB as well as pre-XDR-TB. The percentage of people with pre-XDR-TB tested for susceptibility to linezolid remains low in most parts of the world (Fig. 3.2.17).

Fig. 3.2.17 Percentage of people diagnosed with pre-XDR-TB^a who were tested for susceptibility to linezolid at country level, 2021

Further country-specific details about diagnostic testing for TB, HIV-associated TB and anti-TB drug resistance are available in the Global tuberculosis report app and country profiles.

Data shown on this webpage are as of 29 August 2022 (see Annex 2 of the main report for more details).

Note: The text describing figure 3.2.12 was corrected on 5 January 2023 (previously it stated that the level of testing for rifampicin resistance globally was unchanged between 2020 and 2021).

References