M. J. van der Werf

Prevalence of tuberculous infection and incidence of tuberculosis: a re-assessment of the Styblo rule

OBJECTIVEnTo evaluate the validity of the fixed mathematical relationship between the annual risk of tuberculous infection (ARTI), the prevalence of smear-positive tuberculosis (TB) and the incidence of smear-positive TB specified as the Styblo rule, which TB control programmes use to estimate the incidence of TB disease at a population level and the case detection rate.nnnMETHODSnPopulation-based tuberculin surveys and surveys on prevalence of smear-positive TB since 1975 were identified through a literature search. For these surveys, the ratio between the number of tuberculous infections (based on ARTI estimates) and the number of smear-positive TB cases was calculated and compared to the ratio of 8 to 12 tuberculous infections per prevalent smear- positive TB case as part of the Styblo rule.nnnFINDINGSnThree countries had national population-based data on both ARTI and prevalence of smear-positive TB for more than one point in time. In China the ratio ranged from 3.4 to 5.8, in the Philippines from 2.6 to 4.4, and in the Republic of Korea, from 3.2 to 4.7. All ratios were markedly lower than the ratio that is part of the Styblo rule.nnnCONCLUSIONnAccording to recent country data, there are typically fewer than 8 to 12 tuberculous infections per prevalent smear-positive TB case, and it remains unclear whether this ratio varies significantly among countries. The decrease in the ratio compared to the Styblo rule probably relates to improvements in the prompt treatment of TB disease (by national TB programmes). A change in the number of tuberculous infections per prevalent smear-positive TB case in population-based surveys makes the assumed fixed mathematical relationship between ARTI and incidence of smear-positive TB no longer valid.

Lack of evidence to support policy development for management of contacts of multidrug-resistant tuberculosis patients: two systematic reviews.

BACKGROUNDnExisting international guidelines provide different recommendations for the management of contacts of multidrug-resistant tuberculosis (MDR-TB) patients.nnnOBJECTIVEnTo conduct two systematic reviews with the aim of identifying chemoprophylactic approaches that are effective in contacts of MDR-TB patients to assist in policy making.nnnDESIGNnWe systematically searched the Medline, Embase, Central, LILACS, TRIP and BIOSIS Preview databases for studies on the effectiveness of anti-tuberculosis drugs in preventing active TB in persons at risk of developing MDR-TB. This was done as an update of a systematic review from 2006 using the same methodology. In addition, we searched for studies including persons at risk of developing TB after exposure to non-MDR-TB patients who were treated with anti-tuberculosis drugs other than isoniazid or rifampicin.nnnRESULTSnOf 1195 references assessed in the update, one additional study could be included. As the initial review included two studies, the total number of included studies equals three. One study reported no contacts who developed TB, whether or not they received prophylaxis. The other two studies showed non-significant risk differences of 4% (95%CI -3 to 12), and 5% (95%CI -2 to 11), both in favour of chemoprophylaxis. For the additional review, 2480 references were assessed, but none could be included.nnnCONCLUSIONnThe attention given to MDR-TB in recent years has not resulted in publications on preventive treatment for contacts of MDR-TB patients. The available evidence is not sufficient to support or reject preventive treatment. Furthermore, the combined available evidence is of very low quality.

Molecular surveillance of multi- and extensively drug-resistant tuberculosis transmission in the European Union from 2003 to 2011.

The European Centre for Disease Prevention and Control (ECDC) initiated a project on the molecular surveillance of multi- and extensively drug-resistant tuberculosis (MDR-/XDR-TB) transmission in the European Union (EU) in the period from 2009 to 2011. In total, 2,092 variable number of tandem repeat (VNTR) patterns of MDR-/XDR-TB Mycobacterium tuberculosis isolates were collected, originating from 24 different countries in the period 2003 to 2011. Of the collected VNTR patterns, 45% (n=941) could be assigned to one of the 79 European multiple-country molecular fingerprint clusters and 50% of those (n=470) belonged to one extremely large cluster caused by Beijing strains of one genotype. We conclude that international transmission of MDR-/XDR-TB plays an important role in the EU, especially in the eastern part, and is significantly related to the spread of one strain or clone of the Beijing genotype. Implementation of international cluster investigation in EU countries should reveal underlying factors of transmission, and show how TB control can be improved regarding case finding, contact tracing, infection control and treatment in order to prevent further spread of MDR-/XDR-TB in the EU.

Prevalence of smear-positive tuberculosis in persons aged ⩾15 years in Bangladesh: results from a national survey, 2007–2009

The aim of this study was to determine the nationwide prevalence of smear-positive tuberculosis (TB) in Bangladesh. A multi-stage cluster survey of a random sample of persons aged ≥ 15 years was included in 40 clusters (20 urban, 20 rural). Two sputum samples were collected from study participants and tested initially by fluorescence microscopy and confirmed by the Ziehl-Neelsen method. The crude and adjusted prevalence rates and 95% confidence intervals (CIs) were calculated using standard methods. A total of 33 new smear-positive TB cases were detected among 52 098 individuals who participated in the study. The average participation rate was over 80%. The overall crude prevalence of new smear-positive TB in persons aged ≥ 15 years was estimated as 63.3/100 000 (95% CI 43.6-88.9) and the adjusted prevalence was 79.4/100 000 (95% CI 47.1-133.8). TB prevalence was higher in males (n = 24) and in rural areas (n = 20). The prevalence was highest in the 55-64 years age group (201/100 000) and lowest in 15-24 years age group (43.0/100 000). The prevalence was higher in persons with no education (138.6/100 000, 95% CI 78.4-245.0). The overall prevalence of smear-positive TB was significantly lower than the prevalence estimate of the previous nationwide survey in Bangladesh in 1987-1988 (870/100 000).

Tuberculosis in migrants in low-incidence countries: epidemiology and intervention entry points

As tuberculosis (TB) rates continue to decline in native populations in most low TB incidence countries, the proportion of TB patients born outside their country of residence (foreign-born) increases. Some low-incidence countries have experienced a substantial increase in TB rates related to recent increases in the number of asylum seekers and other migrants from TB-endemic countries. However, average TB rates among the foreign-born in low-incidence countries declined moderately in 2009-2015. TB in foreign-born individuals is commonly the result of reactivation of latent infection with Mycobacterium tuberculosis acquired outside the host country. Transmission is generally low in low-incidence countries, and transmission from migrants to the native population is often modest. Variations in levels and trends in TB notifications among the foreign-born are likely explained by differences and fluctuations in the number and profile of migrants, as well as by variations in TB control, health and social policies in the host countries. To optimise TB care and prevention in migrants from endemic to low-incidence countries, we propose a framework for identifying possible TB care and prevention interventions before, during and after migration. Universal access to high-quality care along the entire migration pathway is critical. Screening for active TB and latent tuberculous infection should be tailored to the TB epidemiology, adapted to the needs of specific migrant groups and linked to treatment. Ultimately, the long-term TB elimination goal can be reached only if global health and socio-economic inequalities are dramatically reduced. Low-incidence countries, most of which are among the wealthiest nations, need to contribute through international assistance.

Drug resistance among tuberculosis cases in the European Union and European Economic Area, 2007 to 2012

The European Union and European Economic Area (EU/EEA) tuberculosis (TB) surveillance system collects detailed information on resistance to TB drugs. Using this information, we provide an overview of the current TB drug resistance situation and trends in the EU/EEA by performing a descriptive analysis, including analysis of treatment outcomes, of the TB cases reported between January 2007 and December 2012. The percentages of TB cases with different drug resistance patterns have been stable with about 90% of the new laboratory-confirmed cases pan-susceptible, 6% monodrug-resistant, 2% polydrug-resistant, 2% multidrug drug-resistant (MDR) TB - excluding extensively drugresistant (XDR) TB -, and 0.2% XDR-TB. In previously treated laboratory-confirmed TB cases, the percentage with MDR-TB excluding XDR-TB declined until 2010 to 16% and remained stable thereafter. During the study period, the percentages of cases with monodrug- and polydrug-resistant TB remained constant at about 8% and 2% whereas the percentage of XDR-TB cases increased slightly to 2.6%. Treatment outcome results for all cases have been stable with overall 77.9% of the pan-susceptible cases, 69.6% of the monoresistant cases, 68.2% of the polyresistant cases, 32.2% of the MDR-TB cases (excluding XDR-TB), and 19.1% of the XDR-TB cases treated successfully. The treatment success rate target for new pulmonary culture-positive MDR-TB cases of 70% has not been reached. In addition, drug resistance surveillance can be improved by more complete reporting of drug susceptibility results and treatment outcome.

Measuring socio-economic data in tuberculosis prevalence surveys.

Addressing social determinants in the field of tuberculosis (TB) has received great attention in the past years, mainly due to the fact that worldwide TB incidence has not declined as much as expected, despite highly curative control strategies. One of the objectives of the World Health Organization Global Task Force on TB Impact Measurement is to assess the prevalence of TB disease in 22 high-burden countries by active screening of a random sample of the general population. These surveys provide a unique opportunity to assess socio-economic determinants in relation to prevalent TB and its risk factors. This article describes methods of measuring the socio-economic position in the context of a TB prevalence survey. An indirect measurement using an assets score is the most feasible way of doing this. Several examples are given from recently conducted prevalence surveys of the use of an assets score, its construction, and the analyses of the obtained data.

Reforming tuberculosis control in Ukraine: results of pilot projects and implications for the national scale-up of DOTS.

The period of economic transition has had severe consequences for health and health systems in Ukraine. The tuberculosis (TB) situation illustrates this. The strategy recommended by the World Health Organization (WHO) for TB, directly observed treatment short-course (DOTS), has the potential to provide real improvements in TB services, forming the basis of the response to the growing epidemic. In 2002, Ukraine, financially supported by USAID and the European Community (EC), began to introduce DOTS through pilot projects in Mariupol and Kyiv City. The aim of this study is to assess the feasibility, effectiveness, health service cost, patient cost, and the cost-effectiveness of these pilots, in order to inform the national scale-up of DOTS. The study finds that DOTS is feasible and has the potential to be both effective and cost-effective in Ukraine. Following this study, Ukraine adopted DOTS as a national TB control strategy in 2005. However, the pilots also found that there are several evidence-related concerns and perverse economic incentives to both providers and patients that will need to be addressed if national scale-up is to be successful. These include concerns related to the treatment of MDR-TB, economic benefits to some patients to remain hospitalized, and payments to providers and health facilities that support current practices. These will need to be addressed if Ukraine is to develop an effective response to its emerging TB epidemic.

External Quality Assessment for Tuberculosis Diagnosis and Drug Resistance in the European Union: A Five Year Multicentre Implementation Study.

Background External quality assurance (EQA) systems are essential to ensure accurate diagnosis of TB and drug-resistant TB. The implementation of EQA through organising regular EQA rounds and identification of training needs is one of the key activities of the European TB reference laboratory network (ERLTB-Net). The aim of this study was to analyse the results of the EQA rounds in a systematic manner and to identify potential benefits as well as common problems encountered by the participants. Methods The ERLTB-Net developed seven EQA modules to test laboratories’ proficiency for TB detection and drug susceptibility testing using both conventional and rapid molecular tools. All National TB Reference laboratories in the European Union and European Economic Area (EU/EEA) Member States were invited to participate in the EQA scheme. Results A total of 32 National TB Reference laboratories participated in six EQA rounds conducted in 2010–2014. The participation rate ranged from 52.9% - 94.1% over different modules and rounds. Overall, laboratories demonstrated very good proficiency proving their ability to diagnose TB and drug-resistant TB with high accuracy in a timely manner. A small number of laboratories encountered problems with identification of specific Non-tuberculous Mycobacteria (NTMs) (N = 5) and drug susceptibility testing to Pyrazinamide, Amikacin, Capreomycin, and Ethambutol (N = 4). Conclusions The European TB Reference laboratories showed a steady and high level of performance in the six EQA rounds. A network such as ERLTB-Net can be instrumental in developing and implementing EQA and in establishing collaboration between laboratories to improve the diagnosis of TB in the EU/EEA.

Tuberculosis notification rate decreases faster in residents of native origin than in residents of foreign origin in the EU/EEA, 2010 to 2015

To estimate trends in tuberculosis (TB) notification rates by geographical origin, we retrieved surveillance data from 2010u2009tou20092015 for 29 European Union and European Economic Area countries. The TB notification rate decreased at an annual rate of 5.3%. The decrease in notification rate was higher in native residents (7.0%) than in those of foreign origin (3.7%). Targeted screening and facilitated access to care and treatment could help prevent and control TB in migrants.