Assessment of body mass-related covariates for rifampicin pharmacokinetics in healthy Caucasian volunteers.

PURPOSE: Currently, body weight-based dosing of rifampicin is recommended. But lately, fat-free mass (FFM) was reported to be superior to body weight (BW). The present evaluation aimed to assess the influence of body mass-related covariates on rifampicin's pharmacokinetics (PK) parameters in more detail using non-linear mixed effects modeling (NLMEM). METHODS: Twenty-four healthy Caucasian volunteers were enrolled in a bioequivalence study, each receiving a test and a reference tablet of 600 mg of rifampicin separated by a wash-out period of at least 9 days. Monolix version 2023R1 was used for NLMEM. Monte Carlo simulations (MCS) were performed to visualize the relationship of body size descriptors to the exposure to rifampicin. RESULTS: A one-compartment model with nonlinear (Michaelis-Menten) elimination and zero-order absorption kinetics with a lag time best described the data. The covariate model including fat-free mass (FFM) on volume of distribution (V/F) and on maximum elimination rate (Vmax/F) lowered the objective function value (OFV) by 56.4. The second-best covariate model of sex on V/F and Vmax/F and BW on V/F reduced the OFV by 51.2. The decrease in unexplained inter-individual variability on Vmax/F in both covariate models was similar. For a given dose, MCS showed lower exposure to rifampicin with higher FFM and accordingly in males compared to females with the same BW and body height. CONCLUSION: Our results indicate that beyond BW, body composition as reflected by FFM could also be relevant for optimized dosing of rifampicin. This assumption needs to be studied further in patients treated with rifampicin.

Medicamentos para Tuberculosis Resistente/Latente ISSS / Medications for resistant/latent tuberculosis ISSS

INTRODUCCIÓN: El presente documento muestra el resultado de la evaluación de la solicitud de incorporación de los medicamentos Delamanid 50 mg tableta, Pretomanid 200 mg tabletas y Rifapentina 150 mg tabletas como parte de la terapia para Tuberculosis Multidrogorresistente (TB-MDR), Tuberculosis Extensamente Drogorrresistente (TB -XDR) y Tuberculosis Latente (ILTB). TECNOLOGÍA: Delamanid 50 mg tableta, Pretomanid 200 mg tabletas, Rifapentina 150 mg tabletas. OBJETIVO: Evaluar la incorporación de las tecnologías en el esquema de tratamiento de Tuberculosis Farmacorresistente y Tuberculosis Latente. OBJETIVO Evaluar la incorporación de las tecnologías en el esquema de tratamiento de Tuberculosis Farmacorresistente y Tuberculosis Latente. MÉTODOS: l. Verificación de disponibilidad local en la Dirección Nacional de Medicamentos (DNM). 2. Investigación en Agencias Reguladoras (AEMPS/EMA/FDA) para verificación de la indicación. 3. Informe Técnico Revisión de la evidencia científica/ Revisión de directrices de la Organización Mundial de la Salud OMS y Guías Clínicas del Ministerio de Salud de El Salvador (MINSAL). 4. Costos de los medicamentos. 5. Conclusiones 6. Recomendaciones. RESULTADOS: Se evaluó información científica disponible, como guías, lineamientos y Evaluaciones de Tecnología Sanitaria, de acuerdo a la evidencia científica disponible, los medicamentos solicitados se encuentran dentro de las directrices para el manejo de Tuberculosis Farmacorresistente y Tuberculosis Latente de la Organización Mundial de la Salud (OMS) y Ministerio de Salud de El Salvador (MINSAL). CONCLUSIONES: Actualmente, los medicamentos solicitados no están comercializados en el país, pero forman parte del Lista de Medicamentos Fondo Estratégico OPS Las Agencias Reguladoras consultadas muestran que los fármacos cuentan con autorización uso para las indicaciones solicitadas Así mismo, las directrices emitidas por la OMS, los fármacos Delamanid 50 mg tableta y Pretornanid 200 mg tabletas están aprobados para el tratamiento de tuberculosis Tuberculosis Multidrogorresistente (TB-MDR) y Tuberculosis Extensamente Drogorrresistente (TB -XDR) Según lo establecido por la OMS y por MINSAL, Rifapentina se puede utilizar como tratamiento preventivo en Tuberculosis Latente (ILTB), tanto en países de incidencia alta como incidencia baja.

Pooling sputum testing to diagnose tuberculosis using xpert MTB/RIF and xpert ultra: a cost-effectiveness analysis.

BACKGROUND: The World Health Organization (WHO) recommends the diagnosis of tuberculosis (TB) using molecular tests, such as Xpert MTB/RIF (MTB/RIF) or Xpert Ultra (Ultra). These tests are expensive and resource-consuming, and cost-effective approaches are needed for greater coverage. METHODS: We evaluated the cost-effectiveness of pooling sputum samples for TB testing by using a fixed amount of 1,000 MTB/RIF or Ultra cartridges. We used the number of people with TB detected as the indicator for cost-effectiveness. Cost-minimization analysis was conducted from the healthcare system perspective and included the costs to the healthcare system using pooled and individual testing. RESULTS: There was no significant difference in the overall performance of the pooled testing using MTB/RIF or Ultra (sensitivity, 93.9% vs. 97.6%, specificity 98% vs. 97%, p-value > 0.1 for both). The mean unit cost across all studies to test one person was 34.10 international dollars for the individual testing and 21.95 international dollars for the pooled testing, resulting in a savings of 12.15 international dollars per test performed (35.6% decrease). The mean unit cost per bacteriologically confirmed TB case was 249.64 international dollars for the individual testing and 162.44 international dollars for the pooled testing (34.9% decrease). Cost-minimization analysis indicates savings are directly associated with the proportion of samples that are positive. If the TB prevalence is ≥ 30%, pooled testing is not cost-effective. CONCLUSION: Pooled sputum testing can be a cost-effective strategy for diagnosis of TB, resulting in significant resource savings. This approach could increase testing capacity and affordability in resource-limited settings and support increased testing towards achievement of WHO End TB strategy.

A cost-benefit algorithm for rapid diagnosis of tuberculosis and rifampicin resistance detection during mass screening campaigns.

BACKGROUND: Active tuberculosis (TB) case finding is important as it helps detect pulmonary TB cases missed by the other active screening methods. It requires periodic mass screening in risk population groups such as prisoners and refugees. Unfortunately, in these risk population groups periodic mass screening can be challenging due to lengthy turnaround time (TAT), cost and implementation constraints. The aim of this study was to evaluate a diagnostic algorithm that can reduce the TAT and cost for TB and Rifampicin resistance (RR) detection. The algorithm involves testing with TB-LAMP followed by Xpert MTB/RIF for positive TB-LAMP cases to diagnose TB during mass campaigns in prisons and refugee camps. METHODS: The National Tuberculosis Control Program (NTCP) organized routine TB mass-screening campaigns in 34 prisons and 3 villages with refugees camps in Cameroon in 2019. TB LAMP was used for initial TB diagnosis and all TB-LAMP positive cases tested with the Xpert MTB/RIF assay to determine RR. TAT and cost benefits analysis of the combined use of TB-LAMP and Xpert MTB/RIF assays was determined and compared to the Xpert MTB/RIF assay when used only. RESULTS: A total of 4075 sputum samples were collected from TB presumptive, 3672 cases in 34 prisons and 403 samples in 3 villages. Of the 4,075 samples screened with TB-LAMP, 135 were TB positive (3.31%) and run on the Xpert MTB/RIF. Of the 135 positives cases, Xpert MTB/RIF revealed 3 were RR (2.22%). The use of TB-LAMP followed by testing with Xpert MTB/RIF for TB and RR detection reduced the TAT by 73.23% in prisons and 74.92% in villages. In addition to a reduced TAT, the two molecular tests used in synergy is cost benefit from year 2 onwards. CONCLUSION: This study demonstrates the advantages of a diagnostic algorithm based on an initial testing with TB-LAMP followed by testing with Xpert MTB/RIF for TB diagnosis. This approach improved early and rapid TB detection with an added advantage of providing RR status. The proposed algorithm is effective and less costly from the second year of implementation and should be used by TB control programs.

Performance Assessment of Xpert MTB/RIF Assay for Detecting Pulmonary Tuberculosis and Rifampin Resistance in a Tertiary Care Hospital in Korea.

In this study, we aimed to assess the performance of the Xpert MTB/RIF assay for the detection of pulmonary tuberculosis compared to the acid-fast bacilli (AFB) smear and culture analysis, and the incidence of rifampin resistance using the drug susceptibility test. The specimens referred for AFB smear and culture analysis and Xpert MTB/RIF assay from April 2015 to March 2018 were retrospectively reviewed. The sensitivity, specificity, and mean cycle threshold (Ct) values obtained in Xpert MTB/RIF assay and for rifampin resistance were analyzed. The results of Xpert MTB/RIF assay for pulmonary tuberculosis were evaluated based on the AFB smear grade. Among 3,840 specimens, 491 were positive in Xpert MTB/RIF assay and 626 in culture analysis. The sensitivity and specificity of Xpert MTB/RIF assay were 75.6% and 99.4%, respectively. The sensitivity of Xpert MTB/RIF assay for smear-positive/culture-positive specimens was 98.6% and that of smear-negative and -trace/culture-positive specimens was 63.1%. The positivity of Xpert MTB/RIF assay for culture-positive specimens was 89.9%, 98.6%, 95.7%, 100.0%, and 100.0% for the smear grades trace, 1+, 2+, 3+, 4+, respectively. The Ct values of 491 specimens significantly decreased as the AFB smear grade increased (P < 0.0001). The Ct values of smear-positive, -trace, and -negative specimens were 21.7 ± 4.2, 26.5 ± 3.9, and 27.4 ± 3.6, respectively. Rifampin resistance evaluated using Xpert MTB/RIF assay and culture analysis exhibited a correlation of 98.3%. The region covered by probe E was the most frequently mutated region (50.0%). Xpert MTB/RIF assay demonstrated reliable performance in detecting pulmonary tuberculosis from smear-positive and culture-positive specimens; however, further improvements are still required to detect smear-negative and culture-positive specimens.

Coverage and fidelity of the Xpert MTB/RIF™ implementation in a high-burden area for pulmonary tuberculosis in Colombia / [Cobertura y fidelidad de la prueba Xpert MTB/RIF™ en un área de alta carga de tuberculosis pulmonar en Colombia].

Introduction: The Xpert MTB/RIF™ is a rapid molecular test that diagnoses tuberculosis and rifampin resistance. Since 2010, it is recommended by the World Health Organization (WHO) and although it was introduced in Colombia since 2012, the results of its implementation are unknown. Objective: To describe the coverage and fidelity in the implementation of the Xpert MTB/RIF™ in patients with pulmonary tuberculosis in a city with a high burden for the disease in Colombia. Materials and methods: We conducted a retrospective, descriptive study of cases from a tuberculosis program in Cali between 2013 and 2019. We estimated the coverage as the total number of tests used compared to the cases registered in the program and the fidelity based on international Xpert MTB/RIF™ implementation protocols. We performed a multivariate analysis of multiple correspondences between the test and the sociodemographic variables. Results: We included 6,328 patients with pulmonary tuberculosis of whom 181 were drugresistant. The Xpert MTB/RIF™ coverage was 10,3% (n=655) with an annual variation between 0.2% and 23%. Loyalty among the highest risk groups of MDR-TB was 46.8%. The use of the test was related to being an Afro-Colombian man between 41 and 60 years of age. Conclusions: The coverage of the Xpert MTB/RIF in Cali is low and its use does not follow the recommended prioritization for its implementation. Implementation strategies are required for its proper use to contribute to the goal of ending tuberculosis.

Introducción. La prueba Xpert MTB/RIF™ es una prueba molecular rápida para el diagnóstico de la tuberculosis y la resistencia a la rifampicina. Desde el 2010 es la recomendada por la Organización Mundial de la Salud (OMS) y, aunque fue introducida en Colombia en el 2012, se desconocen los resultados de su uso. Objetivo. Describir la cobertura y la fidelidad en el uso de la prueba Xpert MTB/RIF™ en pacientes con tuberculosis pulmonar en una ciudad con alta carga de la enfermedad en Colombia. Materiales y métodos. Se hizo un estudio retrospectivo descriptivo de casos del programa de tuberculosis en Cali entre el 2013 y el 2019. La cobertura se estimó como el total de pruebas empleadas en los casos registrados en el programa. La fidelidad se midió con base en los protocolos internacionales de uso de la Xpert MTB/RIF™. Además, se hizo un análisis de correspondencias múltiples entre la prueba y las variables sociodemográficas. Resultados. Se incluyeron 6.328 pacientes con tuberculosis pulmonar, de los cuales 181 eran resistentes a los fármacos. La cobertura total de la Xpert MTB/RIF™ durante el periodo de estudio fue de 10,3 % (n=655), con una variación anual entre 0,2 y 23 %. La fidelidad fue de 46,8 % para los grupos de mayor riesgo de tuberculosis multirresistente (TB-MDR). El uso de la prueba se relacionó con la condición de ser hombre, afrocolombiano, y tener entre 41 y 60 años de edad. Conclusiones. La cobertura de la prueba Xpert MTB/RIF™ en Cali es baja y su uso no responde a la priorización recomendada para su implementación. Se requieren estrategias para promover su uso adecuado, de manera que contribuya a la meta de poner fin a la tuberculosis.

Factors associated with catastrophic total costs due to tuberculosis under a designated hospital service model: a cross-sectional study in China.

BACKGROUND: Certain districts and counties in China designated local general hospital as the designated hospital for tuberculosis (TB) management after the promulgation of the Law of Practicing Physicians in 2009. To our knowledge, there is limited research on catastrophic payments of TB patients under this service model, often with inconsistent conclusions. In addition, there has been no published studies from China using the updated 2018 World Health Organization (WHO) definition of catastrophic total costs due to TB. This study used the latest criterion recommended by the WHO to analyze the incidence of catastrophic total costs for households affected by TB under the designated hospital model and explore its influencing factors. METHODS: A cross-sectional analysis was carried out in all ten designated hospitals in Ningbo, China. Eligible pulmonary TB cases confirmed by sputum culture of Mycobacterium tuberculosis were recruited and surveyed from September 2018 to October 2018. We evaluated catastrophic total costs using total costs for TB treatment exceeding 20% of the household's annual pre-TB income. A sensitivity analysis was performed while varying the thresholds. The least absolute shrinkage and selection operator (LASSO) regression were applied to select variables, and multiple logistic regression analysis were used to identify the determinants of catastrophic total costs. RESULTS: A total of 672 patients were included, with a median age of 41 years old. The rate of catastrophic total costs of surveyed households was 37.1%, and that of households affected by MDR was 69.6%. Medical cost accounted for more than 60% of the total cost. 57.7% cases were hospitalized. The hospitalization rates of patients with no comorbidities, no severe adverse drug reactions, and rifampin-sensitive TB were 53.9, 54.9, and 55.3%, respectively. Patients in the poorest households had the highest hospitalization rates (Q1:54.8%, Q2:61.4%, Q3:52.2%, Q4:49.5%, Q5:69.7%, P = 0.011) and the highest incidence of severe adverse drug reactions (Q1:29.6%, Q2:19.6%, Q3:28.0%, Q4:33.7%, Q5:35.3%, P = 0.034). Factors such as elderly, minimum living security, unemployed before or after illness, poor economic status, seeking medical care outside the city, hospitalization, absence of local basic medical insurance coverage and MDR were positively associated with catastrophic costs. CONCLUSION: Substantial proportions of patients and households affected by pulmonary TB faced catastrophic economic risks in Ningbo, China. The existing policies that focus on expanding the coverage of basic medical insurance and economic protection measures (such as cash transfers to compensate low-income households for direct non-medical costs and income loss) might be insufficient. Tailored program that mitigate inappropriate healthcare and address equity of care delivery are worthy of attention.

Comparative fitness analysis of D-cycloserine resistant mutants reveals both fitness-neutral and high-fitness cost genotypes.

Drug resistant infections represent one of the most challenging medical problems of our time. D-cycloserine is an antibiotic used for six decades without significant appearance and dissemination of antibiotic resistant strains, making it an ideal model compound to understand what drives resistance evasion. We therefore investigated why Mycobacterium tuberculosis fails to become resistant to D-cycloserine. To address this question, we employed a combination of bacterial genetics, genomics, biochemistry and fitness analysis in vitro, in macrophages and in mice. Altogether, our results suggest that the ultra-low rate of emergence of D-cycloserine resistance mutations is the dominant biological factor delaying the appearance of clinical resistance to this antibiotic. Furthermore, we also identified potential compensatory mechanisms able to minimize the severe fitness costs of primary D-cycloserine resistance conferring mutations.

Tuberculosis treatment in the private healthcare sector in India: an analysis of recent trends and volumes using drug sales data.

BACKGROUND: There is a pressing need for systematic approaches for monitoring how much TB treatment is ongoing in the private sector in India: both to cast light on the true scale of the problem, and to help monitor the progress of interventions currently being planned to address this problem. METHODS: We used commercially available data on the sales of rifampicin-containing drugs in the private sector, adjusted for data coverage and indication of use. We examined temporal, statewise trends in volumes (patient-months) of TB treatment from 2013 to 2016. We additionally analysed the proportion of drugs that were sold in combination packaging (designed to simplify TB treatment), or as loose pills. RESULTS: Drug sales suggest a steady trend of TB treatment dispensed by the private sector, from 18.4 million patient-months (95% CI 17.3-20.5) in 2013 to 16.8 patient-months (95% CI 15.5-19.0) in 2016. Overall, seven of 29 states in India accounted for more than 70% of national-level TB treatment volumes, including Uttar Pradesh, Maharashtra and Bihar. The overwhelming majority of TB treatment was dispensed not as loose pills, but in combination packaging with other TB drugs, accounting for over 96% of private sector TB treatment in 2017. CONCLUSIONS: Our findings suggest consistent levels of TB treatment in the private sector over the past 4 years, while highlighting specific states that should be prioritized for intervention. Drug sales data can be helpful for monitoring a system as large, disorganised and opaque as India's private sector.

[Incremental cost-effectiveness of the second Xpert MTB/RIF assay for detection of Mycobacterium tuberculosis].

Objective: To study the incremental cost-effectiveness of the second Xpert assay in detection of Mycobacterium tuberculosis (Mtb) and rifampicin (RIF) resistance. Methods: We continuously collected 2 896 specimens from suspected tuberculosis patients who had undergone 2 Xpert tests in a week from March 2015 to March 2018, including 2 402 suspected tuberculosis patients with 1 523 males and 879 females, with an average age of 50 years. Among them, 2 144 specimens of sputum and 258 cases of bronchoalveolar lavage fluid were collected. We also enrolled 494 patients with suspected extrapulmonary tuberculosis, 318 males and 176 females, with an average age of 42 years. Among them, 157 pleural effusion specimens, 106 cerebrospinal fluid specimens, 34 urine specimens and 197 pus specimens were collected. All specimens were subjected to two Xpert tests, smear microscopy, liquid rapid culture (BACTEC MGIT 960), and positively cultured bacteria were tested for drug susceptibility. Results: Among the 2 896 specimens from suspected tuberculosis patients, either one of the two Xpert test results was positive (including both tests were positive, the same below) in 1 639 patients, and 1 502 (91.6%) were positive in the first Xpert tests. The additional 137 (8.4%) test results were positive in the second tests. According to the smear test results, all specimens were divided into the smear negative group and the smear positive group. The second Xpert test was significantly higher than the smear-positive group (14.86%, 3.2%, P<0.001), and the extrapulmonary tuberculosis group was higher than the tuberculosis group (11.2%, 8.0%, P=0.12).Of the susceptibility test results, a total of 371 were rifampicin-resistant specimens. The first Xpert detected 91.4% (339/371), and the second Xpert detected the additional 8.1% (30/371).The cost increase of the second test was very significant. Tests were calculated at 650 yuan per time, the tuberculosis group was 1 184 yuan and 13 696 yuan(P<0.001); the extrapulmonary tuberculosis group was 1 755 yuan and 13 961 yuan(P<0.001). In the test of specimens of tuberculosis and extrapulmonary tuberculosis, the smear-negative specimen cost increase of the second Xpert test was lower than that of the smear-positive specimen. Conclusion: The second xpert test showed significant value-added cost-effectiveness in the diagnosis of tuberculosis.

Clinical Pharmacokinetics and Pharmacodynamics of Rifampicin in Human Tuberculosis.

The introduction of rifampicin (rifampin) into tuberculosis (TB) treatment five decades ago was critical for shortening the treatment duration for patients with pulmonary TB to 6 months when combined with pyrazinamide in the first 2 months. Resistance or hypersensitivity to rifampicin effectively condemns a patient to prolonged, less effective, more toxic, and expensive regimens. Because of cost and fears of toxicity, rifampicin was introduced at an oral daily dose of 600 mg (8-12 mg/kg body weight). At this dose, clinical trials in 1970s found cure rates of ≥ 95% and relapse rates of < 5%. However, recent papers report lower cure rates that might be the consequence of increased emergence of resistance. Several lines of evidence suggest that higher rifampicin doses, if tolerated and safe, could shorten treatment duration even further. We conducted a narrative review of rifampicin pharmacokinetics and pharmacodynamics in adults across a range of doses and highlight variables that influence its pharmacokinetics/pharmacodynamics. Rifampicin exposure has considerable inter- and intra-individual variability that could be reduced by administration during fasting. Several factors including malnutrition, HIV infection, diabetes mellitus, dose size, pharmacogenetic polymorphisms, hepatic cirrhosis, and substandard medicinal products alter rifampicin exposure and/or efficacy. Renal impairment has no influence on rifampicin pharmacokinetics when dosed at 600 mg. Rifampicin maximum (peak) concentration (Cmax) > 8.2 µg/mL is an independent predictor of sterilizing activity and therapeutic drug monitoring at 2, 4, and 6 h post-dose may aid in optimizing dosing to achieve the recommended rifampicin concentration of ≥ 8 µg/mL. A higher rifampicin Cmax is required for severe forms TB such as TB meningitis, with Cmax ≥ 22 µg/mL and area under the concentration-time curve (AUC) from time zero to 6 h (AUC6) ≥ 70 µg·h/mL associated with reduced mortality. More studies are needed to confirm whether doses achieving exposures higher than the current standard dosage could translate into faster sputum conversion, higher cure rates, lower relapse rates, and less mortality. It is encouraging that daily rifampicin doses up to 35 mg/kg were found to be safe and well-tolerated over a period of 12 weeks. High-dose rifampicin should thus be considered in future studies when constructing potentially shorter regimens. The studies should be adequately powered to determine treatment outcomes and should include surrogate markers of efficacy such as Cmax/MIC (minimum inhibitory concentration) and AUC/MIC.

Pathways and associated costs of care in patients with confirmed and presumptive tuberculosis in Tanzania: A cross-sectional study.

OBJECTIVE: To assess pathways and associated costs of seeking care from the onset of symptoms to diagnosis in patients with confirmed and presumptive tuberculosis (TB). DESIGN: Cross-sectional study. SETTING: District hospital in Dar es Salaam, Tanzania. PARTICIPANTS: Bacteriologically confirmed TB and presumptive TB patients. PRIMARY AND SECONDARY OUTCOME MEASURES: We calculated distance in metres and visualised pathways to healthcare up to five visits for the current episode of sickness. Costs were described by medians and IQRs, with comparisons by gender and poverty status. RESULTS: Of 100 confirmed and 100 presumptive TB patients, 44% of confirmed patients sought care first at pharmacies after the onset of symptoms, and 42% of presumptive patients did so at hospitals. The median visits made by confirmed patients was 2 (range 1-5) and 2 (range 1-3) by presumptive patients. Patients spent a median of 31% of their monthly household income on health expenditures for all visits. The median total direct costs were higher in confirmed compared with presumptive patients (USD 27.4 [IQR 18.7-48.4] vs USD 19.8 [IQR 13.8-34.0], p=0.02), as were the indirect costs (USD 66.9 [IQR 35.5-150.0] vs USD 46.8 [IQR 20.1-115.3], p<0.001). The indirect costs were higher in men compared with women (USD 64.6 [IQR 31.8-159.1] vs USD 55.6 [IQR 25.1-141.1], p<0.001). The median total distance from patients' household to healthcare facilities for patients with confirmed and presumptive TB was 2338 m (IQR 1373-4122) and 2009 m (IQR 986-2976) respectively. CONCLUSIONS: Patients with confirmed TB have complex pathways and higher costs of care compared with patients with presumptive TB, but the costs of the latter are also substantial. Improving access to healthcare and ensuring integration of different healthcare providers including private, public health practitioners and patients themselves could help in reducing the complex pathways during healthcare seeking and optimal healthcare utilisation.

Household contact investigation for the detection of tuberculosis in Vietnam: economic evaluation of a cluster-randomised trial.

BACKGROUND: Active case finding is recommended as an important strategy to control tuberculosis, particularly in low-income and middle-income countries with a high prevalence of the disease. However, the costs and cost-effectiveness of active case finding are unclear due to the absence of evidence from randomised trials. We assessed the costs and cost-effectiveness of an active case finding strategy in Vietnam, where there is a high prevalence of tuberculosis. METHODS: We conducted an economic evaluation alongside the Active Case Finding in Tuberculosis (ACT2) trial-a pragmatic cluster-randomised controlled trial in 70 districts across eight provinces of Vietnam. Patients aged 15 years and older with smear-positive pulmonary tuberculosis were recruited to the trial if they lived with one or more other household members. Household contacts were verbally invited to the clinic by the index patient with tuberculosis. ACT2 compared a combination of active and passive case finding with usual care (passive case finding) of household contacts of patients with tuberculosis from a health system perspective. Clustering occurred at the district and household level. Districts were the unit of randomisation, and we used minimisation to ensure balance of intervention and control districts within each province. In the intervention group, participants were invited to attend screening at baseline, 6 months, 12 months, and 24 months. We determined health-care costs with a standardised national costing survey and reported results in 2017 $US. The primary outcome of our study was disability-adjusted life years (DALYs) averted over a 24-month period. ACT2 was registered prospectively with the Australian and New Zealand Clinical Trials Registry, number ACTRN126.100.00600044. FINDINGS: Between Aug 11, 2010, and Aug 11, 2015, 10 964 index patients and 25 707 household contacts completed the ACT2 study. There were 10 069 household contacts in the intervention group and 15 638 household contacts in the control group. The incremental cost-effectiveness ratio per DALY averted was $544 (330-1375). INTERPRETATION: Active case finding was shown to be highly cost-effective in a setting with a high prevalence of tuberculosis. Investment in the wide-scale implementation of this programme in Vietnam should be strongly supported. FUNDING: Australian National Health and Medical Research Council.

Mechanisms of fitness cost reduction for rifampicin-resistant strains with deletion or duplication mutations in rpoB.

Rifampicin resistance (RifR) is caused by mutations in rpoB, encoding the ß-subunit of RNA polymerase. RifR mutations generally incur a fitness cost and in resistant isolates are frequently accompanied by compensatory mutations in rpoA, rpoB or rpoC. Previous studies of fitness compensation focused on RifR caused by amino acid substitutions within rpoB. RifR is also caused by deletion and duplication mutations in rpoB but it is not known whether or how such mutants can ameliorate their fitness costs. Using experimental evolution of Salmonella carrying RifR deletion or duplication mutations we identified compensatory amino acid substitution mutations within rpoA, rpoB or rpoC in 16 of 21 evolved lineages. Additionally, we found one lineage where a large deletion was compensated by duplication of adjacent amino acids (possibly to fill the gap within the protein structure), two lineages where mutations occurred outside of rpoABC, and two lineages where a duplication mutant reverted to the wild-type sequence. All but the two revertant mutants maintained the RifR phenotype. These data suggest that amino acid substitution mutations are the major compensatory mechanism regardless of the nature of the primary RifR mutation.

Comparative evaluation of Xpert MTB/RIF assay with multiplex polymerase chain reaction for the diagnosis of tuberculous meningitis.

BACKGROUND: Rapid and specific diagnosis of tuberculous meningitis (TBM) is of paramount importance to decrease morbidity and mortality. Therefore, the present study was undertaken to compare the efficacy of Xpert MTB/RIF assay (GXpert) and multiplex PCR (MPCR) using three targets (IS6110, MPB64 and protein B) for diagnosing tuberculous meningitis. METHODS: GXpert and MPCR were performed on cerebrospinal fluid samples of 225 patients out of which 80 were culture-positive confirmed cases of TBM, 100 were 'suspected' cases of TBM and 45 were non-TBM controls. rpoB gene sequencing was done for diagnosing rifampicin (Rif) resistance in all positive cases. RESULTS: GXpert and MPCR were positive in 91/180 (50.5%) and 157/180 (87.2%) confirmed or suspected TBM patients respectively. Both the tests were negative in all 45 controls. Rif resistance was detected in 14 cases by GXpert and in 13 cases by MPCR. Rif resistance was confirmed in 13 cases with rpoB gene sequencing. There was one case of false Rif resistance detected by GXpert which was Rif susceptible on rpoB gene sequencing. Cost of doing MPCR was less than USD1 whereas GXpert required USD10 per isolate. CONCLUSION: MPCR has a higher sensitivity than GXpert for diagnosing TBM. MPCR is a robust and cost effective method for diagnosis of TBM in low-resource and high-endemic countries.

How has the Zimbabwe mycobacterial culture and drug sensitivity testing system among re-treatment tuberculosis patients functioned during the scale-up of the Xpert MTB/RIF assay?

Background: In Zimbabwe, while the Xpert MTB/RIF assay is being used for diagnosing tuberculosis and rifampicin-resistance, re-treatment tuberculosis (TB) patients are still expected to have culture and drug sensitivity testing (CDST) performed at national reference laboratories for confirmation. The study aim was to document the Xpert MTB/RIF assay scale-up and assess how the CDST system functioned for re-treatment TB patients. Methods: We performed an ecologic study using national aggregate data. Results: Use of the Xpert MTB/RIF assay increased from 11 829 to 68 153 between 2012 and 2016. Xpert assays worked well, with successful tests in more than 90% of cases, TB detection rates at 15-17% and rifampicin resistance in <10%. During Xpert scale-up, the number of sputum specimens from re-treatment TB patients reaching national reference laboratories for CDST increased from 12% to 51%. In terms of laboratory performance, culture contamination increased from 3% to 17%, positive cultures from 13% to 17% and successful CDST from 6% to 14%: the proportion of CDST showing any resistance to rifampicin averaged 44%. From 2009 to 2016, the proportion of notified re-treatment TB patients with successful CDST increased from <1% to 7%. Conclusions: While components of Zimbabwe's CDST system for re-treatment TB patients showed some changes during the scale-up of the Xpert MTB/RIF assay, overall performance was poor. The country must either invest in improving CDST performance or in advanced molecular diagnostic technology.

Improving rifampicin-resistant tuberculosis diagnosis using Xpert® MTB/RIF: modelling interventions and costs.

SETTING: Cape Town, South Africa. OBJECTIVE: To model the diagnosis of rifampicin-resistant tuberculosis (RR-TB) and laboratory costs of smear/culture and Xpert-based algorithms and the effect of varying adherence and human immunodeficiency virus (HIV) testing in the Xpert-based algorithm. METHODS: We used a validated operational model (100 000 population) and published laboratory cost data. We estimated the number and cost of RR-TB cases identified using the smear/culture- and Xpert-based algorithms. We modelled varying adherence and different levels of known HIV status against the Xpert-based algorithm. RESULTS: The number of RR-TB cases identified increased from 603 with smear/culture to 1178 with the Xpert-based algorithm (100% adherence; 60% knew their HIV status). The overall laboratory cost increased from US$1 073 858 to US$2 430 050 and the cost per RR-TB case identified increased from US$1781 to US$2063 in the respective algorithms. When adherence to the Xpert-based algorithm was increased from 50% to 100% (60% knew their HIV status), the number of RR-TB cases identified increased from 721 to 1178. CONCLUSION: The Xpert-based algorithm is efficient in identifying RR-TB, as the increase in costs is offset by the increase in the number of cases identified. Adherence to the Xpert-based algorithm is important to ensure that all presumptive TB cases receive the benefit of simultaneous TB and RR-TB testing.

Assessment of GeneXpert GxAlert platform for multi-drug resistant tuberculosis diagnosis and patients' linkage to care in Tanzania.

OBJECTIVE: The gap between patients diagnosed with multi-drug resistant tuberculosis (MDR-TB) and enrolment in treatment is one of the major challenges in tuberculosis control programmes. A 4-year (2013-2016) retrospective review of patients' clinical data and subsequent in-depth interviews with health providers were conducted to assess the effectiveness of the GeneXpert GxAlert platform for MDR-TB diagnosis and its impact on linkage of patients to care in Tanzania. RESULTS: A total of 782 new rifampicin resistant cases were notified, but only 242 (32.3%) were placed in an MDR-TB regimens. The remaining 540 (67.07%) patients were not on treatment, of which 103 patients had complete records on the GxAlert database. Of the 103 patients: 39 were judged as untraceable; 27 died before treatment; 12 were treated with first-line anti-TBs; 9 repeat tests did not show rifampicin resistance; 15 were not on treatment due to communication breakdown, and 1 patient was transferred outside the country. In-depth interviews with health providers suggested that the pre-treatment loss for the MDR-TB patients was primarily attributed to health system and patients themselves. We recommend strengthening the health system by developing and implementing well-defined interventions to ensure all diagnosed MDR-TB patients are accurately reported and timely linked to treatment.