Modeling the impact of novel diagnostic tests on pediatric and extrapulmonary tuberculosis

BACKGROUND: Extrapulmonary tuberculosis (EPTB) and most pediatric TB cannot be diagnosed using sputum-based assays. The epidemiological impact of different strategies to diagnose EPTB and pediatric TB is unclear. METHODS: We developed a dynamic epidemic model of TB in a hypothetical population with epidemiological characteristics similar to India. We evaluated the impact of four alternative diagnostic test platforms on adult EPTB and pediatric TB mortality over 10 years: (1) Nucleic acid amplification test optimized for diagnosis of EPTB (“NAAT-EPTB”); (2) NAAT optimized for pediatric TB (“NAAT-Peds”); (3) more deployable NAAT for sputum-based diagnosis of adult pulmonary TB (“point-of-care (POC) sputum NAAT”); and (4) more deployable NAAT capable of diagnosing all forms of TB using non-invasive, non-sputum specimens (“POC non-sputum NAAT”). RESULTS: NAAT-EPTB lowered adult EPTB mortality by a projected 7.6% (95% uncertainty range [UR]: 6.5-8.8%). NAAT-Peds lowered pediatric TB mortality by 6.8% (UR: 4.9-8.4%). POC sputum NAAT, though only able to diagnose pulmonary TB, reduced projected pediatric TB deaths by 13.3% (UR: 4.6-15.7%) and adult EPTB deaths by 8.4% (UR 2.0-9.3%) simply by averting transmission of disease. POC non-sputum NAAT had the greatest effect, lowering pediatric TB mortality by 34.7% (UR: 26.8-38.7), and adult EPTB mortality by 38.5% (UR: 30.7-41.2). The relative impact of a POC sputum NAAT (i.e., enhanced deployability) versus NAAT-EPTB (i.e., enhanced ability to specifically diagnose TB-NSP) on adult EPTB mortality depends most strongly on factors that influence transmission, with settings of higher transmission (e.g., higher per-person transmission rate, lower diagnostic rate) favoring POC sputum NAAT. CONCLUSION: Although novel tests for pediatric TB and EPTB are likely to reduce TB mortality, major reductions in pediatric and EPTB incidence and mortality also require better diagnostic tests for adult pulmonary TB that reach a larger population. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/1471-2334-14-477) contains supplementary material, which is available to authorized users

Serological Testing Versus Other Strategies for Diagnosis of Active Tuberculosis in India: A Cost-Effectiveness Analysis

This cost-effectiveness study shows that sputum smear microscopy is the most cost-effective test for active tuberculosis (TB) in India, and liquid culture plus microscopy is more cost-effective for TB diagnosis than serological tests

Strategies to Accelerate HIV Care and Antiretroviral Therapy Initiation After HIV Diagnosis: A Randomized Trial.

: Determine the effectiveness of strategies to increase linkage to care after testing HIV positive at mobile HIV testing in South Africa. : Unmasked randomized controlled trial. : Recruitment of adults testing HIV positive and not currently in HIV care occurred at 7 mobile HIV counseling and testing units in urban, periurban, and rural South Africa with those consenting randomized 1:1:1:1 into 1 of 4 arms. Three strategies were compared with standard of care (SOC): point-of-care CD4 count testing (POC CD4), POC CD4 plus longitudinal strengths-based counseling (care facilitation; CF), and POC CD4 plus transport reimbursement (transport). Participants were followed up telephonically and through clinic records and analyzed with an intention-to-treat analysis. : From March 2013 to October 2014, 2558 participants were enrolled, of whom 160 were excluded postrandomization. Compared with the SOC arm where 298 (50%) reported having entered care, linkage to care was 319 (52%) for POC CD4, hazard ratio (HR) 1.0 [95% confidence interval (CI): 0.89 to 1.2, P = 0.6]; 331 (55%) for CF, HR: 1.1 (95% CI: 0.84 to 1.3, P = 0.2); and 291 (49%) for transport, HR 0.97 (95% CI: 0.83 to 1.1, P = 0.7). Linkage to care verified with clinical records that occurred for 172 (29%) in the SOC arm; 187 (31%) in the POC CD4 arm, HR: 1.0 (95% CI: 0.86 to 1.3, P = 0.6); 225 (38%) in the CF arm, HR: 1.4 (95% CI: 1.1 to 1.7, P = 0.001); and 180 (31%) in the transport arm, HR: 1.1 (95% CI: 0.88 to 1.3, P = 0.5). : CF improved verified linkage to care from 29% to 38%.<br/

The Impact and Cost of Scaling up GeneXpert MTB/RIF in South Africa

We estimated the incremental cost and impact on diagnosis and treatment uptake of national rollout of Xpert MTB/RIF technology (Xpert) for the diagnosis of pulmonary TB above the cost of current guidelines for the years 2011 to 2016 in South Africa.We parameterised a population-level decision model with data from national-level TB databases (n = 199,511) and implementation studies. The model follows cohorts of TB suspects from diagnosis to treatment under current diagnostic guidelines or an algorithm that includes Xpert. Assumptions include the number of TB suspects, symptom prevalence of 5.5%, annual suspect growth rate of 10%, and 2010 public-sector salaries and drug and service delivery costs. Xpert test costs are based on data from an in-country pilot evaluation and assumptions about when global volumes allowing cartridge discounts will be reached.At full scale, Xpert will increase the number of TB cases diagnosed per year by 30%-37% and the number of MDR-TB cases diagnosed by 69%-71%. It will diagnose 81% of patients after the first visit, compared to 46% currently. The cost of TB diagnosis per suspect will increase by 55% to USD 60-61 and the cost of diagnosis and treatment per TB case treated by 8% to USD 797-873. The incremental capital cost of the Xpert scale-up will be USD 22 million and the incremental recurrent cost USD 287-316 million over six years.Xpert will increase both the number of TB cases diagnosed and treated and the cost of TB diagnosis. These results do not include savings due to reduced transmission of TB as a result of earlier diagnosis and treatment initiation

How can mathematical models advance tuberculosis control in high HIV prevalence settings?

Existing approaches to tuberculosis (TB) control have been no more than partially successful in areas with high human immunodeficiency virus (HIV) prevalence. In the context of increasingly constrained resources, mathematical modelling can augment understanding and support policy for implementing those strategies that are most likely to bring public health and economic benefits. In this paper, we present an overview of past and recent contributions of TB modelling in this key area, and suggest a way forward through a modelling research agenda that supports a more effective response to the TB-HIV epidemic, based on expert discussions at a meeting convened by the TB Modelling and Analysis Consortium. The research agenda identified high-priority areas for future modelling efforts, including 1) the difficult diagnosis and high mortality of TB-HIV; 2) the high risk of disease progression; 3) TB health systems in high HIV prevalence settings; 4) uncertainty in the natural progression of TB-HIV; and 5) combined interventions for TB-HIV. Efficient and rapid progress towards completion of this modelling agenda will require co-ordination between the modelling community and key stakeholders, including advocates, health policy makers, donors and national or regional finance officials. A continuing dialogue will ensure that new results are effectively communicated and new policy-relevant questions are addressed swiftly

Feasibility of a streamlined tuberculosis diagnosis and treatment initiation strategy.

OBJECTIVE: To assess the feasibility of a streamlined strategy for improving tuberculosis (TB) diagnostic evaluation and treatment initiation among patients with presumed TB. DESIGN: Single-arm interventional pilot study at five primary care health centers of a streamlined, SIngle-saMPLE (SIMPLE) TB diagnostic evaluation strategy: 1) examination of two smear results from a single spot sputum specimen using light-emitting diode fluorescence microscopy, and 2) daily transportation of smear-negative sputum samples to Xpert® MTB/RIF testing sites. RESULTS: Of 1212 adults who underwent sputum testing for TB, 99.6% had two smears examined from the spot sputum specimen. Sputum was transported for Xpert testing within 1 clinic day for 83% (907/1091) of the smear-negative patients. Of 157 (13%) patients with bacteriologically positive TB, 116 (74%) were identified using sputum smear microscopy and 41 (26%) using Xpert testing of smear-negative samples. Anti-tuberculosis treatment was initiated in 142 (90%) patients with bacteriologically positive TB, with a median time to treatment of 1 day for smear-positive patients and 6 days for smear-negative, Xpert-positive patients. CONCLUSION: The SIMPLE TB strategy led to successful incorporation of Xpert testing and rapid treatment initiation in the majority of patients with bacteriologically confirmed TB in a resource-limited setting

Predictors of isoniazid preventive therapy completion among adults newly diagnosed with HIV in rural Malawi.

SETTING: To reduce the risk of tuberculosis (TB) among individuals with human immunodeficiency virus (HIV) infection, the World Health Organization recommends at least 6 months of isoniazid preventive therapy (IPT). Completion of IPT remains a major challenge in resource-limited settings. OBJECTIVE: To evaluate predictors of IPT completion in individuals newly diagnosed with HIV. DESIGN: Predictors of IPT completion among adults newly diagnosed with HIV in rural Malawi were evaluated using a multilevel logistic regression model. RESULTS: Of 974 participants who screened negative for active TB and were started on IPT, 732 (75%) completed treatment. Only one IPT-eligible individual refused treatment. Participants who were aged <25 years (compared with those aged 45 years, adjusted OR [aOR] 0.33, 95%CI 0.18-0.60) and male (compared to non-pregnant females, aOR 0.57, 95%CI 0.37-0.88) had lower odds of IPT completion. CONCLUSION: IPT provision at the time of initial HIV diagnosis was highly acceptable in rural Malawi; three quarters of those who initiated IPT successfully completed therapy. We observed lower odds of completion among males and among female participants aged <25 years. Additional efforts may be needed to ensure IPT completion among males and young females who have recently been diagnosed with HIV

Predictors of isoniazid preventive therapy completion among adults newly diagnosed with HIV in rural Malawi.

SETTING: To reduce the risk of tuberculosis (TB) among individuals with human immunodeficiency virus (HIV) infection, the World Health Organization recommends at least 6 months of isoniazid preventive therapy (IPT). Completion of IPT remains a major challenge in resource-limited settings. OBJECTIVE: To evaluate predictors of IPT completion in individuals newly diagnosed with HIV. DESIGN: Predictors of IPT completion among adults newly diagnosed with HIV in rural Malawi were evaluated using a multilevel logistic regression model. RESULTS: Of 974 participants who screened negative for active TB and were started on IPT, 732 (75%) completed treatment. Only one IPT-eligible individual refused treatment. Participants who were aged <25 years (compared with those aged 45 years, adjusted OR [aOR] 0.33, 95%CI 0.18-0.60) and male (compared to non-pregnant females, aOR 0.57, 95%CI 0.37-0.88) had lower odds of IPT completion. CONCLUSION: IPT provision at the time of initial HIV diagnosis was highly acceptable in rural Malawi; three quarters of those who initiated IPT successfully completed therapy. We observed lower odds of completion among males and among female participants aged <25 years. Additional efforts may be needed to ensure IPT completion among males and young females who have recently been diagnosed with HIV

Rapid Diagnosis of Tuberculosis with the Xpert MTB/RIF Assay in High Burden Countries: A Cost-Effectiveness Analysis

A cost-effectiveness study by Frank Cobelens and colleagues reveals that Xpert MTB/RIF is a cost-effective method of tuberculosis diagnosis that is suitable for use in low- and middle-income settings