Annual Risk Of Tuberculous Infection Research Articles

Tuberculin reactivity in schoolchildren, Kassala State, Sudan.

Tuberculin skin test (TST) is widely used for the assessment of Bacillus Calmette-Guérin (BCG) vaccine efficacy and screening of latent TB infection (LTBI). Poor or no data are available on the reactivity of tuberculin in Kassala State. The aim of the present study was to assess the response to the BCG vaccine and to estimate the prevalence of LTBI and the annual rate annual risk of tuberculous infection (ARTI) among vaccinated school children using TST. School-based cross-sectional study was conducted in three localities of Kassala State during 2016-2018. A cluster random sampling method was used for the enrolment. Five tuberculin units of 0.1 mL were injected intradermally in the left forearm of 2568 school children aged 5-15 years. The test was performed after the assessment of child health, nutrition status, and BCG scar status. Tuberculin reaction size was interpreted after 48-72 h. The collected data were analyzed using SPSS (v 20). The classical method was used to estimate ARTI. Overall, there was no reaction in 81.5% of children. Only 0.66% of children had induration 10 mm-28 mm, indicating the prevalence of latent TB with an annual risk of 0.1%. Tuberculin reactivity was statistically significant affected by child age, gender, geographical location, and nutrition status (P < 0.05), whereas BCG scar status had no effect (P > 0.05). The study documented a high proportion of tuberculin nonreactivity irrespective of BCG vaccination status and provides data on the prevalence of latent infection among studied groups. Further studies are needed to address the reasons of low and nonreactivity of tuberculin, and evaluation of the BCG vaccine is recommended.

Estimating tuberculosis incidence from primary survey data: a mathematical modeling approach.

SUMMARYBACKGROUND:There is an urgent need for improved estimations of the burden of tuberculosis (TB).OBJECTIVE:To develop a new quantitative method based on mathematical modelling, and to demonstrate its application to TB in India.DESIGN:We developed a simple model of TB transmission dynamics to estimate the annual incidence of TB disease from the annual risk of tuberculous infection and prevalence of smear-positive TB. We first compared model estimates for annual infections per smear-positive TB case using previous empirical estimates from China, Korea and the Philippines. We then applied the model to estimate TB incidence in India, stratified by urban and rural settings.RESULTS:Study model estimates show agreement with previous empirical estimates. Applied to India, the model suggests an annual incidence of smear-positive TB of 89.8 per 100 000 population (95%CI 56.8–156.3). Results show differences in urban and rural TB: while an urban TB case infects more individuals per year, a rural TB case remains infectious for appreciably longer, suggesting the need for interventions tailored to these different settings.CONCLUSIONS:Simple models of TB transmission, in conjunction with necessary data, can offer approaches to burden estimation that complement those currently being used.

Numbers of tuberculosis cases: dreams and reality.

Use of estimated numbers of tuberculosis (TB) cases for planning purposes in some sub-Saharan countries. To document the uncertainties of official World Health Organization estimates and problems encountered in using them for planning. Brief review of the methods used in estimation, using different sub-Saharan countries to illustrate problems. The annual risk of tuberculous infection, used for many years to calculate estimates, is no longer considered a valid method. New methods are based on an assessment of the completeness of TB notification data (the Onion Model) and prevalence surveys of bacteriologically proven pulmonary TB cases; however, these are subject to bias and are very imprecise. Examples from sub-Saharan countries reflect these difficulties and show that official estimates vary substantially, by up to a quarter of the initial values. Donors, particularly the Global Fund, rely on these estimates and push countries to arbitrarily increase planned numbers of notified cases to improve 'case detection rates'. Use of estimated numbers to monitor progress in TB control may be counterproductive, costly and risky. It would be much more realistic to accept that low-income countries plan their strategies based on TB notifications rather than on case detection rates that are more dream than reality.

Risk of tuberculous infection in adolescents and adults in a rural community in Ethiopia.

The incidence of tuberculosis (TB) in sub-Saharan Africa is one of the highest in the world. To evaluate the prevalence of TB, the annual risk of tuberculous infection (ARTI) and associated risk factors in rural Ethiopia. A tuberculin skin test was performed among 2743 individuals in a rural community of Ethiopia around Ginci town, west of Addis Ababa, to estimate the prevalence of tuberculin reactivity and to assess factors associated with tuberculous infection. Among 2743 volunteer participants, test results were available for 2640, 691 (26.2%) of whom had an identifiable bacille Calmette-Guérin (BCG) scar; 221 (8.3%) reported household contact with a known TB case. The overall prevalence of TST reactions of ⩾ 10 mm was 29.7%. The ARTI was estimated at 1.7%. Tuberculin reactivity varied with age, sex, income and history of household contact with a TB case. Presence of BCG scar was not related to tuberculin reactivity. Our findings indicate that despite an effective TB control programme, TB transmission rates are still high in rural Ethiopia. Provision of isoniazid prophylaxis in close contacts of active TB cases among the poorest population groups may reduce TB incidence.

Latent tuberculous infection in schoolchildren and contact tracing in Matlosana, North West Province, South Africa.

This is a cross-sectional study to estimate the prevalence of latent tuberculous infection (LTBI) and the annual risk of tuberculous infection (ARTI) among a sample of children aged 5 and 7 years in Matlosana, South Africa. LTBI prevalence was significantly higher in children aged 7 years (n = 704) (19.7%, 95%CI 16.75-22.65) than in those aged 5 years (212/1401, 15.1%, 95%CI 13.23-16.97) (P = 0.0075). The ARI was 2.9% (95%CI 2.2-3.6).

Annual risk of tuberculous infection measured using serial skin testing, Orel Oblast, Russia, 1991-2005.

To compare trends in direct annual risk of tuberculous infection (ARTI) during 1991-2005 in relation to tuberculosis (TB) incidence and to indirect estimates of ARTI derived from the prevalence of tuberculin skin test (TST) positivity in schoolchildren in Orel Oblast, Russia. In 2005, we abstracted annual TST results and vaccination histories from a representative sample of schoolchildren in Orel Oblast, Russia, where bacille Calmette-Guerin (BCG) vaccination and annual TST of children are nearly universal. We calculated direct ARTI based on the percentage of children tested with TST conversions each year, excluding conversions following BCG vaccination. We analysed records from 13 206 children, with a median of 10 recorded TST results per child. The ARTI increased from 0.2% in 1991 to 1.6% in 2000, paralleling trends in TB incidence. Similar results were observed when the ARTI was estimated based on prevalence of infection among children aged 3-5 years using a 12 mm cut-off to define TST positivity. Results differed substantially when 10 or 15 mm cut-offs were used or when prevalence was determined among children aged 6-8 years. ARTI measured through TST conversion increased as TB incidence increased in Orel Oblast. ARTI measured through serial TSTs can thus provide an indicator of changing trends in TB incidence.

High prevalence and risk factors associated with latent tuberculous infection in two Colombian prisons.

Two prisons in Medellín and Itagüí, Colombia. To determine the prevalence of tuberculin skin test (TST) positivity in prisoners and the annual risk of tuberculous infection (ARTI), to identify risk factors associated with a positive result, and to describe progression to active disease. Cross-sectional study. Inmates were included if time of incarceration was ⩾1 year and excluded if subjects had had previous or active tuberculosis (TB), or conditions that could hamper TST administration or interpretation. We screened 1014 inmates. The overall prevalence of TST positivity was 77.6%. The first TST administration resulted in 66% positivity, and the second TST an additional 11.6%. In Prison One, the ARTI was 5.09% in high TB incidence cell blocks and 2.72% in low TB incidence blocks. In Prison Two, the ARTI was 2.77%. Risk factors associated with TST positivity were history of previous incarceration and length of incarceration. Among all those included in the study, four individuals developed active pulmonary TB. Prevalence of TST positivity in prisoners and the ARTI were higher than in the general population, but differed between prisons; it is important to apply a second TST to avoid an overestimation of converters during follow-up.

Tuberculin survey in Bangladesh, 2007–2009: prevalence of tuberculous infection and implications for TB control

To assess the prevalence of tuberculous infection and the annual risk of tuberculous infection (ARTI) for 2007-2009 in Bangladesh, approximately 45 years after the first tuberculin survey in 1964-1966. A tuberculin survey was conducted along with the National Tuberculosis Disease Prevalence Survey in 2007-2009. This was a multistaged community-based, cross-sectional survey, including 17,718 children aged 5-14 years. The prevalence of tuberculous infection was estimated using the mixture method and a cut-off point of ≥ 8 mm. The prevalence of infection was 10.0% (interquartile range [IQR] 8.6-12.2) in children aged 5-9 years and 17.9% (IQR 15.4-20.2) in those aged 10-14 years using the mixture analysis. Prevalence was 12.4% (95% confidence interval [CI] 11.7-13.1) in children aged 5-9 years and 22.6% (95%CI 21.6-23.4) in those aged 10-14 years using a cut-off point of ≥ 8 mm. The estimated ARTI was respectively 1.5% and 1.7% in 5-9 and 10-14 year olds using the mixture method and respectively 1.9% and 2.1% using the cut-off method. The moderate reduction in the prevalence of infection and slow decline of the ARTI after two decades of DOTS implementation indicates considerable ongoing transmission.

First national tuberculin survey in Viet Nam: characteristics and association with tuberculosis prevalence

To estimate the prevalence of infection with Mycobacterium tuberculosis and the annual risk of tuberculous infection (ARTI) and to compare this with the prevalence of tuberculosis (TB) over study clusters and households. A nationwide, stratified cluster sample survey was carried out in 2006-2007 in Viet Nam to assess the prevalence of infection with M. tuberculosis. A representative sample of children aged 6-14 years underwent a tuberculin skin test (TST) using the Mantoux method. Of 23,160 children registered, 21,487 (92.8%) were tested and read and available for analysis. Using a cut-off point of 10 mm, the estimated prevalence of TST positivity was 16.7%, and the ARTI was 1.7% (95%CI 1.5-1.8). Higher infection rates were found in urban than in rural and remote areas, and infection rates increased with age. There was significant association between the prevalence of TB disease and infection at the cluster level (regression coefficient 0.54, 95%CI 0.06-1.01, P = 0.027, correlation coefficient R(2) 0.120). Children with a (recent) case of TB in the household were 1.6 times more likely to be TST-positive than children in households with no recent cases (P < 0.05). The estimated nationwide ARTI was 1.7%. TST positivity was associated with the presence of a TB case in the household.

Errata.

IN THE ARTICLE entitled 'Trends in the annual risk of tuberculous infection in India' by V. K. Chadha, R. Sarin, P. Narang, K. R. John, K. K. Chopra, R. Jitendra, D. K. Mendiratta, V. Vohra, A. N. Shashidhara, G. Muniraj, P. G. Gopi, P. Kumar (Int J Tuberc Lung Dis 2013; 17(3): 312-319; http://dx.doi.org/10.5588/ijtld.12.0330), the affiliation for G. Muniraj should have read Department of Community Medicine, Christian Medical College, Vellore, Tamil Nadu.

Annual risk of tuberculous infection among schoolchildren in Bhutan

School-based survey in the mountainous nation of Bhutan. To estimate the annual risk of tuberculous infection (ARTI) among children aged 6-8 years. A national-level tuberculin survey was carried out among children attending 64 schools selected by two-stage cluster sampling. The study population was comprised of children without and with bacille Calmette-Guérin (BCG) scar. Tuberculin testing was performed using 2 tuberculin units of purified protein derivative RT23. The maximum transverse diameter of induration was measured at 48-72 h. Of 6087 satisfactorily test-read children, 82% had a BCG scar. The frequency distribution of tuberculin reaction sizes in all children (with and without BCG scar) did not reveal the mode for tuberculous reactions. The mode seen at 17 mm among children without BCG scar was applied to estimate the prevalence of infection among all children using the mirror-image method. Estimation was also undertaken by shifting the mode by 1 mm on either side. The ARTI computed from the prevalence thus estimated varied between 0.2% and 0.7%. There was no difference in the prevalence of infection by BCG scar status, implying that the estimated ARTI was not influenced by BCG-induced tuberculin sensitivity. The ARTI has declined in Bhutan compared to the 1991 survey estimate of 1.9%.

Trends in the annual risk of tuberculous infection in India

Twenty-four districts in India. To evaluate trends in annual risk of tuberculous infection (ARTI) in each of four geographically defined zones in the country. Two rounds of house-based tuberculin surveys were conducted 8-9 years apart among children aged 1-9 years in statistically selected clusters during 2000-2003 and 2009-2010 (Surveys I and II). Altogether, 184,992 children were tested with 1 tuberculin unit (TU) of purified protein derivative (PPD) RT23 with Tween 80 in Survey I and 69,496 children with 2TU dose of PPD in Survey II. The maximum transverse diameter of induration was measured about 72 h after test administration. ARTI was computed from the prevalence of infection estimated using the mirror-image method. Estimated ARTI rates in different zones varied between 1.1% and 1.9% in Survey I and 0.6% and 1.2% in Survey II. The ARTI declined by respectively 6.1% and 11.7% per year in the north and west zones; no decline was observed in the south and east zones. National level estimates were respectively 1.5% and 1.0%, with a decline of 4.5% per year in the intervening period. Although a decline in ARTI was observed in two of the four zones and at national level, the current ARTI of about 1% in three zones suggests that further intensification of TB control activities is required.

Trend in Annual Risk of Tuberculous Infection in North India

SettingSix selected districts in Northern India.ObjectivesTo find out the trend in Annual risk of tuberculous infection (ARTI) in north India.Study DesignTwo rounds of community level surveys were conducted during 2000–2001 and 2009–10 respectively. Representative samples of children 1–9 years of age were tuberculin tested and maximum transverse diameter of induration was recorded in mm at about 72 hours. ARTI was computed from the estimated Prevalence of infection using mirror-image technique and anti-mode method.ResultsARTI was found to decline from 1.9% (confidence interval: 1.7–2.1) at round I to 1.1% (confidence interval: 0.8–1.3) at round II at the rate of 8% per year during the intervening period.ConclusionA significant reduction in the risk of tuberculous infection among children was observed between two rounds of surveys carried out at an interval of about 9 years.

Annual Risk of Tuberculous Infection Using Different Methods in Communities with a High Prevalence of TB and HIV in Zambia and South Africa

BackgroundThe annual risk of tuberculous infection (ARTI) is a key epidemiological indicator of the extent of transmission in a community. Several methods have been suggested to estimate the prevalence of tuberculous infection using tuberculin skin test data. This paper explores the implications of using different methods to estimate prevalence of infection and ARTI. The effect of BCG vaccination on these estimates is also investigated.Methodology/Principal FindingsTuberculin surveys among school children in 16 communities in Zambia and 8 in South Africa (SA) were performed in 2005, as part of baseline data collection and for randomisation purposes of the ZAMSTAR study. Infection prevalence and ARTI estimates were calculated using five methods: different cut-offs with or without adjustments for sensitivity, the mirror method, and mixture analysis. A total of 49,835 children were registered for the surveys, of which 25,048 (50%) had skin tests done and 22,563 (90%) of those tested were read. Infection prevalence was higher in the combined SA than Zambian communities. The mirror method resulted in the least difference of 7.8%, whereas that estimated by the cut-off methods varied from 12.2% to 17.3%. The ARTI in the Zambian and SA communities was between 0.8% and 2.8% and 2.5% and 4.2% respectively, depending on the method used. In the SA communities, the ARTI was higher among the younger children. BCG vaccination had little effect on these estimates.Conclusions/SignificanceARTI estimates are dependent on the calculation method used. All methods agreed that there were substantial differences in infection prevalence across the communities, with higher rates in SA. Although TB notification rates have increased over the past decades, the difference in cumulative exposure between younger and older children is less dramatic and a rise in risk of infection in parallel with the estimated incidence of active tuberculosis cannot be excluded.

CORRELATION OF THREE MYCOBACTERIAL SMEARS AND CHEST RADIOGRAPHY WITH CD4 T LYMPHOCYTE COUNT IN HIV-SEROPOSITIVE PATIENTS PRESENTING WITH RESPIRATORY SYMPTOMS

PURPOSE: In India, Tuberculosis [TB] is the most common opportunistic infection in people living with HIV/AIDS. About 40% of the population in India is estimated to be infected with TB bacillus. The annualincidence of smear positive TB is estimated to be 75 per 100,000 population (based on Annual Risk of Tuberculous Infection (ARTI) study. It is estimated that 50 to 60 % of HIV infected people will develop TB disease in their lifetime when compared to 10% of HIV negative persons infected with TB. Three Mycobacterial smears on two consecutive days and chest radiography can aid us in the diagnosis of tuberculosis as according to the Revised National Tuberculosis Control Program Guidelines followed in India. CD4 T Lymphocyte count enables us to understand the patients' immune status.

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

To 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. Population-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. Three 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. According 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.

The benefits and risks of bacille Calmette-Guérin vaccination among infants at high risk for both tuberculosis and severe combined immunodeficiency: assessment by Markov model

BackgroundBacille Calmette-Guérin (BCG) vaccine is given to Canadian Aboriginal neonates in selected communities. Severe reactions and deaths associated with BCG have been reported among infants born with immunodeficiency syndromes. The main objective of this study was to estimate threshold values for severe combined immunodeficiency (SCID) incidence, above which BCG is associated with greater risk than benefit.MethodsA Markov model was developed to simulate the natural histories of tuberculosis (TB) and SCID in children from birth to 14 years. The annual risk of tuberculous infection (ARI) and SCID incidence were varied in analyses. The model compared a scenario of no vaccination to intervention with BCG. Appropriate variability and uncertainty analyses were conducted. Outcomes included TB incidence and quality-adjusted life years (QALYs).ResultsIn sensitivity analyses, QALYs were lower among vaccinated infants if the ARI was 0.1% and the rate of SCID was higher than 4.2 per 100,000. Assuming an ARI of 1%, this threshold increased to 41 per 100,000. In uncertainty analyses (Monte Carlo simulations) which assumed an ARI of 0.1%, QALYs were not significantly increased by BCG unless SCID incidence is 0. With this ARI, QALYs were significantly decreased among vaccinated children if SCID incidence exceeds 23 per 100,000. BCG is associated with a significant increase in QALYs if the ARI is 1%, and SCID incidence is below 5 per 100,000.ConclusionThe possibility that Canadian Aboriginal children are at increased risk for SCID has serious implications for continued BCG use in this population. In this context, enhanced TB Control – including early detection and treatment of infection – may be a safer, more effective alternative.

Annual risk of tuberculous infection — time for an update?

Thissectionlooksbacktosomeground-breakingcontributionstopublichealth,reproducingthemintheiroriginalformandaddingacommentary on their significance from a modern-day perspective. To complement the theme of this month’s Bulletin, MartienW. Borgdorffreviewsthe1988documentbyGeorgeM.Cauthen,AntonioPio&H.GerardtenDamontheannualriskoftuberculousinfection that constituted the basis for many statistics on tuberculosis. The original, unpublished except as a WHO document, isreproduced below.

Annual risk of tuberculous infection. 1988.

I. INTRODUCTION Risk of infection in a population is in many respects the most informative index of the magnitude of the tuberculosis problem (Sutherland, 1976; Pio, 1984). The risk of infection at a particular rime indicates the current magnitude of the incidence and prevalence of infectious cases (Styblo, 1985) and also indicates the magnitude of the tuberculosis problem years into the future. An observed decline in the risk of infection would be the earliest indicator of a decline in the epidemic cycle of tuberculosis, resulting from tuberculosis control activities or improvements in living standards. A rising risk of infection would be an early indicator of changes in the other direction, signalling the introduction of new risk factors, such as the spread of human immunodeficiency virus (HIV) infection. It is known that risk of infection bas been declining for many years in developed countries, but remains at high levels in many developing countries (Styblo, 1984). In developing countries in the last decade, a number of surveys of infection prevalence have been carried out in national populations as well as in smaller populations. Therefore a project was carried out to assess the current level and trend in the risk of infection in developing countries by reviewing and assembling tuberculin skin test survey data available since 1975. II. METHODS Tuberculin skin test data collected since 1975 for populations in developing countries were assembled from reports to the World Health Organization and from the published literature. Data from surveys of childhood age groups that were judged of sufficient quality were selected in order to provide as valid and up to date an assessment as practical of the magnitude of the risk of infection. Comparable prior data for the same countries were also selected in order to judge whether the risk of infection is likely to have declined. Prevalence of infection observed in childhood age groups was used to derive the average annual risk of infection that would have resulted in the observed cumulative prevalence rate. Choosing younger age groups allows the calculated average annual risk to be bracketed within a relatively narrow period of time between the average birth date of the group and the date of the survey (Styblo et al, 1969), Each survey was judged on the basis of available documentation for ability to represent the population and to detect the proportion infected at a particular time. A sample survey was judged to have measured the proportion infected in the target population if the probability sampling design and the estimation method appeared correct in concept and conduct, and skin testing technique appeared adequate to measure the proportion infected in the sampling units. Basis for selection Surveys were selected which met most of the following criteria: Specified the sampling design including the sampling frame, staging, stratification, sampling units, allocation, sampling weights, and estimation formulas and documentation to support that the design was followed with adequate coverage. Provided reaction-size distributions for surveyed age groups and for bacteriologically confirmed cases from the same population in order to assess the definition of infection and in order to judge technique. Documented type and strength of antigen used, technique of administration and reading, and quality control procedures. Specified the methods used to detect and eliminate persons with a history of BCG vaccination, and described BCG policy and actual coverage in the population age group surveyed. Data assembled from selected surveys: The area population represented and the survey period. In the youngest age ranges for which sufficient numbers were tested and read, the number tested and read, the number counted as infected with M. tuberculosis, and the mean age. …

Comparison of effectiveness of BCG vaccination and preventive therapy in Japanese settings, with special emphasis on the sensitivity and specificity of tuberculin testing

BCG vaccination in low prevalence countries is controversial. Most discussions have been done by the comparison of benefit, side effect and cost of BCG vaccination. No discussion has been done on the disadvantage of BCG vaccination from the point of view of loss of sensitivity and specificity of tuberculin test on the diagnosis of LTBI. Three groups, i.e. the BCG vaccination group with preventive therapy under worsened sensitivity and specificity of tuberculin test due to previous BCG, no intervention group and non BCG vaccination group with preventive therapy under standard sensitivity and specificity of tuberculin test were set up. The target population was a cohort of Japanese who are born at the year with 0.1% annual risk of tuberculous infection. The TB incidence, TB related mortality (including death by BCG and preventive therapy), TB related loss of DALY (disability adjusted life years), and direct medical cost of the above three groups, for the cohort only and the cohort including secondary TB cases from the clinical cases in the cohort. Under the current program conditions, the merit of BCG vaccination is greater than the merit obtained from the preventive therapy without BCG. Although the medical direct cost is lowest among the preventive therapy group without BCG, next without BCG or preventive therapy and highest among BCG group. Under BCG group, too extensive screening for LTBI does not reduce the loss of TB related DALY, whereas in the non BCG group, extensive screening will help to reduce the loss of TB related DALY and if more extensive screening can be done, the loss of TB related DALY in the non BCG group can be less than that in the BCG group. At present extensiveness of screening for LTBI and BCG vaccination contribute to the reduction of TB and loss of TB related DALY. Possible extensive screening without BCG may be able to reduce loss of TB related DALY in comparison to the BCG vaccination group.