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Despite the observed clinical benefits of nirmatrelvir/ritonavir (NMV/r), it is uncertain whether Taiwan will continue covering NMV/r for high-risk individuals with mild-to-moderate coronavirus disease 2019 (COVID-19). This analysis assessed the impact of sustained utilization of NMV/r on COVID-19-associated healthcare resource utilization (HCRU) and mortality from the Taiwanese health authority perspective (THAP). A decision tree model estimated the incremental number of clinical events associated with NMV/r utilization over a 30-day period. Model results compared (1) a base case using current rates of NMV/r from the THAP, and (2) a hypothetical scenario assuming the current supply of NMV/r is not extended in Taiwan. NMV/r utilization rates included 80% and 0% in the base case and hypothetical scenario, respectively. Outcomes included the number of hospitalizations involving a general ward (GW) stay, intensive care unit (ICU) stay, and mechanical ventilation (MV) use, as well as the number of bed days, symptom days, and hospitalization deaths. Based on epidemiologic data, 150,255 patients with COVID-19 were eligible for treatment from the THAP. In the hypothetical scenario, HCRU increased by 175% compared to the base case, including increases in hospitalizations involving GW, ICU, and MV use (differences: 2067; 623; 591, respectively), bed days (difference: 51,521), symptom days (difference: 51,714), and deaths (difference: 480). Findings indicate that sustained utilization of NMV/r from the THAP reduces the clinical burden of mild-to-moderate COVID-19 through the reduced incidence of COVID-19-related HCRU and deaths., Competing Interests: Conflicts of InterestM.S., J.B. and J.L. are employees of Stratevi, LLC, which received funding to conduct this research. T.M., S.-T.H. and Y.-M.Y. are employees of Pfizer Inc., and Y.C. is an employee of Pfizer Investment Co., Ltd. T.M., Y.-M.Y. and Y.C. currently own or have previously owned company shares in Pfizer. This research was funded by Pfizer Inc., (© 2024 by the authors.)

Background: In Japan, medical expenses for COVID-19 treatment transitioned from full public funding support to out-of-pocket (OOP) payment by patients plus partial public support in October 2023, and public support fully ended in March 2024. This study evaluated the clinical and economic impacts of initiating OOP payments., Research Design and Methods: To assess the impact on prescription rates, we compared the prescription rates of antivirals from the 4-month pre- to post-OOP payment initiation period using a claims database. Subsequently, a budget impact model assessed the impacts of a hypothetical decline in the prescription rates on COVID-19-related hospitalizations, deaths, and direct medical costs for antiviral prescription and hospitalization., Results: The antiviral prescription rate per 100 patients decreased from 17.5 for the pre-OOP payment initiation period to 11.5 for the post-OOP payment initiation period, that is, a change of - 34.3%. With prescription rate decreases of 40%, 60%, and 80%, the hospitalizations would increase annually by 22,533 (3.3%), 33800 (5.0%), and 45,066 (6.6%), respectively. The total costs would increase by JPY9.5 billion (USD67.3 million; 0.7%), JPY14.3 billion (USD100.9 million; 1.0%), and JPY19.0 billion (USD134.5 million; 1.3%), respectively., Conclusions: Higher OOP payment decreased the antiviral prescription rate, potentially leading to clinical and economic loss.

Background: Although COVID-19 morbidity is significantly lower in pediatrics than in adults, the risk of severe COVID-19 may still pose substantial health care resource burden. This study aimed to describe health care resource utilization (HCRU) and costs associated with COVID-19 in pediatrics 1-17 years old in England., Methods: A population-based retrospective cohort study of pediatrics with COVID-19 using Clinical Practice Research Datalink (CPRD Aurum) primary care data and, where available, linked Hospital Episode Statistics Admitted Patient Care secondary care data. HCRU and associated costs to the National Health Service were stratified by age, risk of severe COVID-19 and immunocompromised status, separately for those with and without hospitalization records (hospitalized cohort: COVID-19 diagnosis August 2020-March 2021; primary care cohort: COVID-19 diagnosis August 2020-January 2022)., Results: This study included 564,644 patients in the primary care cohort and 60 in the hospitalized cohort. Primary care consultations were more common in those 1-4 years of age (face-to-face: 4.3%; telephone: 6.0%) compared with those 5-11 (2.0%; 2.1%) and 12-17 years of age (2.2%; 2.5%). In the hospitalized cohort, mean (SD) length of stay was longer [5.0 (5.8) days] among those 12-17 years old (n = 24) than those 1-4 [n = 15; 1.8 (0.9) days] and 5-11 years old [n = 21; 2.8 (2.1) days]., Conclusions: Most pediatrics diagnosed with COVID-19 were managed in the community. However, hospitalizations were an important driver of HCRU and costs, particularly for those 12-17 years old. Our results may help optimize the management and resource allocation of COVID-19 in this population., (Copyright © 2023 The Author(s). Published by Wolters Kluwer Health, Inc.)

Objectives: Nirmatrelvir/ritonavir (NMV/r) is an orally administered antiviral indicated for the outpatient treatment of patients with mild-to-moderate COVID-19 at high risk for disease progression to severe illness. We estimated the cost-effectiveness of NMV/r versus best supportive care for patients with mild-to-moderate COVID-19 at high risk for progression to severe illness from a US health sector perspective., Methods: A cost-effectiveness model was developed using a short-term decision-tree (1 year) followed by a lifetime 2-state Markov model (alive and dead). The short-term decision-tree captured costs and outcomes associated with the primary infection and healthcare utilization; survivors of the short-term decision-tree were followed until death assuming US quality-adjusted life years (QALYs), adjusted in the short-term for survivors of mechanical ventilation. Baseline rate of hospitalization and NMV/r effectiveness were taken from an Omicron-era US real-world study. Remaining inputs were informed by previous COVID-19 studies and publicly available US sources. Sensitivity analyses were conducted for all model inputs to test the robustness of model results., Results: NMV/r was found to decrease COVID-19 related hospitalizations (-0.027 per infected case) increase QALYs (+0.030), decrease hospitalization costs (-$1110), and increase total treatment cost (+$271), resulting in an incremental cost-effectiveness ratio of $8931/QALY. Results were most sensitive to baseline risk of hospitalization and NMV/r treatment effectiveness parameters. The probabilistic analysis indicated that NMV/r has a >99% probability of being cost-effective at a $100 000 willingness-to-pay threshold., Conclusions: NMV/r is cost-effective vs best supportive care for patients at high risk for severe COVID-19 from a US health sector perspective., Competing Interests: Author Disclosures Links to the individual disclosure forms provided by the authors are available here., (Copyright © 2023 International Society for Pharmacoeconomics and Outcomes Research, Inc. Published by Elsevier Inc. All rights reserved.)

Aims: Reporting of hospitalization cost data for the National Health Service in England evolved substantially in the past decades which may have led to inconsistency in capturing the average cost of hospitalizations in appraisals of new health technologies. Our aim was to systematically review the estimation of hospitalization costs in appraisals for the National Institute for Health and Care Excellence (NICE) and the Joint Committee on Vaccination and Immunisation (JCVI), to identify potential heterogeneity and its drivers. A case study was used to explore the impact of alternative cost estimates on economic evaluations., Methods: Systematic review of past NICE appraisals and published economic evaluations to inform the JCVI. Hospitalization cost data reported in each appraisal were extracted and separately re-calculated to inform descriptive analysis and linear regression. Deterministic sensitivity analysis was performed on an existing cost-effectiveness model of pneumococcal disease in adults, and a best practice framework was developed to support standardization of cost estimation in future appraisals., Results: Length of stay (LoS) was accounted for in 4/118 (3.38%) currency codes across 29 appraisals. LoS and adjustment for complication and comorbidity score were key drivers of differences between cost estimates. There was a statistically significant negative average cost difference of -£1,235 (reported cost < calculated cost) for when accounting for LoS or not. On average, the range of reported costs overestimated hospitalization costs at minimum by £1,511 and underestimated these at maximum by £6,566, suggesting high levels of heterogeneity. In the case study, using spell costs resulted in estimating greater cost savings with the new technology which became dominant compared to the standard of care., Conclusions: Results show high heterogeneity in the estimation of hospitalization costs across appraisals in England over the past decade. More detailed HTA guidance may potentially increase consistency among appraisals of new health technologies.

Objectives: To quantify direct costs and healthcare resource utilisation (HCRU) associated with acute COVID-19 in adults in England., Design: Population-based retrospective cohort study using Clinical Practice Research Datalink Aurum primary care electronic medical records linked to Hospital Episode Statistics secondary care administrative data., Setting: Patients registered to primary care practices in England., Population: 1 706 368 adults with a positive SARS-CoV-2 PCR or antigen test from August 2020 to January 2022 were included; 13 105 within the hospitalised cohort indexed between August 2020 and March 2021, and 1 693 263 within the primary care cohort indexed between August 2020 and January 2022. Patients with a COVID-19-related hospitalisation within 84 days of a positive test were included in the hospitalised cohort., Main Outcome Measures: Primary and secondary care HCRU and associated costs ≤4 weeks following positive COVID-19 test, stratified by age group, risk of severe COVID-19 and immunocompromised status., Results: Among the hospitalised cohort, average length of stay, including critical care stays, was longer in older adults. Median healthcare cost per hospitalisation was higher in those aged 75-84 (£8942) and ≥85 years (£8835) than in those aged <50 years (£7703). While few (6.0%) patients in critical care required mechanical ventilation, its use was higher in older adults (50-74 years: 8.3%; <50 years: 4.3%). HCRU and associated costs were often greater in those at higher risk of severe COVID-19 than in the overall cohort, although minimal differences in HCRU were found across the three different high-risk definitions. Among the primary care cohort, general practitioner or nurse consultations were more frequent among older adults and the immunocompromised., Conclusions: COVID-19-related hospitalisations in older adults, particularly critical care stays, were the primary drivers of high COVID-19 resource use in England. These findings may inform health policy decisions and resource allocation in the prevention and management of COVID-19., Competing Interests: Competing interests: JY, KMA, MR, LJM, CT, TM, KN, DM, Tamuno Alfred, MA and JLN are employees of Pfizer and may hold stock or stock options. KKR, TT, PP, BEB and RW are employees of Adelphi Real World, which received funds from Pfizer to conduct the study and develop the manuscript., (© Author(s) (or their employer(s)) 2023. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Background: Nirmatrelvir/ritonavir (NMV/r) is indicated for the treatment of mild-to-moderate COVID-19 in adults who are at high risk for progression to severe COVID-19. NMV/r has also been authorized for emergency use by the US Food and Drug Administration for the treatment of mild-to-moderate COVID-19 in pediatric patients (aged 226512 years and weighing at least 40 kg) who are at high risk for progression to severe COVID-19. Understanding the budget impact of introducing NMV/r for the treatment of adults with COVID-19 is of key interest to US payers., Objective: To estimate the annual budget impact of introducing NMV/r in a US commercial health plan setting in the current Omicron COVID-19 era., Methods: A budget impact model was developed to assess the impact of NMV/r on health care costs in a hypothetical 1-million-member commercial health insurance plan over a 1-year period in the US population; clinical and cost inputs were derived from published literature with a focus on studies in the recent COVID-19 era that included vaccinated population and predominance of the Omicron variant. In the base-case analysis, it was assumed the only effect of NMV/r was a reduction in incidence (not severity) of hospitalization or death; its potential effect on post-COVID conditions was assessed in a scenario analysis. Outcomes included the number of hospitalizations, total cost, per patient per year (PPPY) costs, and per member per month (PMPM) costs. Sensitivity and scenario analyses were conducted to assess uncertainty around key model inputs., Results: An estimated 29,999 adults were eligible and sought treatment with oral antiviral for COVID-19 over 1 year. The availability of NMV/r was estimated to reduce the number of hospitalizations by 647 with a total budget impact of $2,733,745, $91 PPPY, and $0.23 PMPM. NMV/r was cost saving when including post-COVID conditions with a -$1,510,780 total budget impact, a PPPY cost of -$50, and a PMPM cost of -$0.13. Sensitivity analyses indicated results were most sensitive to the risk of hospitalization under supportive care, risk of hospitalization with NMV/r treatment and cost of NMV/r., Conclusions: Treatment with NMV/r in the current COVID-19 era is estimated to result in substantial cost offsets because of reductions in hospitalization and modest budget impact to potential overall cost savings.

Infectious diseases are a leading cause of morbidity and mortality worldwide with vaccines playing a critical role in preventing deaths. To better understand the impact of low vaccination rates and previous epidemics on infectious disease rates, and how these may help to understand the potential impacts of the current coronavirus disease 2019 (COVID-19) pandemic, a targeted literature review was conducted. Globally, studies suggest past suboptimal vaccine coverage has contributed to infectious disease outbreaks in vulnerable populations. Disruptions caused by the COVID-19 pandemic have contributed to a decline in vaccination uptake and a reduced incidence in several infectious diseases; however, these rates have increased following the lifting of COVID-19 restrictions with modeling studies suggesting a risk of increased morbidity and mortality from several vaccine-preventable diseases. This suggests a window of opportunity to review vaccination and infectious disease control measures before we see further disease resurgence in populations and age-groups currently unaffected.

Objectives: Despite the current pneumococcal vaccination program in England for older adults and adults with underlying conditions, disease burden remains high. We evaluated cost-effectiveness of 20-valent pneumococcal conjugate vaccine (PCV20) compared to current pneumococcal recommendations for adults in England., Methods: Lifetime outcomes/costs of invasive pneumococcal disease (IPD) and community-acquired pneumonia (CAP) among adults aged 65-99 years and adults aged 18-64 years with underlying conditions in England were projected using a deterministic cohort model. Vaccination with PCV20 was compared with 23-valent pneumococcal polysaccharide vaccine (PPV23) from the National Health Service perspective., Results: PCV20 was cost saving compared with PPV23 in base case and most sensitivity analyses. In the base case, replacing PPV23 with PCV20 prevented 7,789 and 140,046 cases of IPD and hospitalized CAP, respectively, and 22,199 associated deaths, resulting in incremental gain of 91,375 quality-adjusted life-years (QALYs) and incremental savings of £160M. In probabilistic sensitivity analyses, PCV20 (vs. PPV23) was cost saving in 85% of simulations; incremental cost per QALY was below £30,000 in 99% of simulations., Conclusions: PCV20 vaccination in adults aged 65-99 years and those aged 18-64 years with underlying comorbidities in England is expected to prevent more hospitalizations, save more lives, and yield lower overall costs than current recommendations for PPV23.

Background: Despite use of 23-valent pneumococcal polysaccharide vaccine (PPV23) in England, disease burden among at-risk adults remains high. We evaluated the public health and budgetary impact of 20-valent pneumococcal conjugate vaccine (PCV20) compared to the current adult pneumococcal vaccination program., Methods: Five-year outcomes and costs of invasive pneumococcal disease (IPD) and community-acquired pneumonia (CAP) among adults aged 65-99 years and adults aged 18-64 years with underlying conditions in England were projected using a deterministic cohort model. Hypothetical vaccination with PCV20 versus PPV23 was compared from the National Health Service (NHS) perspective., Results: Replacing PPV23 with PCV20 would prevent 785 IPD hospitalizations, 11,751 CAP hospitalizations, and 1,414 deaths over 5 years, and would reduce medical care costs by £48.5 M. With vaccination costs higher by £107.2 M, projected net budgetary impact is £58.7 M. The budgetary impact would be greatest in year 1 (£26.3 M), and would decrease over time (to £1.6 M by year 5). The average budget increase (£11.7 M/year) represents <0.01% of the Department of Health and Social Care total budget and <3% of the vaccine budget., Conclusions: Use of PCV20 among adults currently eligible for PPV23 in England would substantially reduce the burden of pneumococcal disease, with modest budgetary impact.

Objective: Accurate and up-to-date figures of the cost of community-acquired pneumonia (CAP) hospitalization are needed to understand the associated economic burden for public health decision-makers. Recent estimates are lacking, and previously published estimates differ markedly. Our objective was to estimate the current mean cost to the UK National Health Service (NHS) for adult hospitalized CAP., Methods: All CAP hospitalizations in 2019 for those aged ≥18 years were identified from English Hospital Episode Statistics (HES). Each hospitalization was mapped to the tariff cost paid to the care provider within the NHS, including critical care costs and accounting for length of stay and complexity of the case. Mean hospitalization costs were estimated in total and in individuals with defined underlying comorbidities., Results: A mean cost of £3,904 was estimated for 187,251 CAP admissions providing a total cost of approximately £731 million per annum. The mean cost was £3,402, excluding critical care costs, and £11,654 for critical care episodes in the 4.4% of admissions receiving this care. Groups at high risk of CAP had higher mean costs, ranging from £4,458 for people with diabetes to £5,215 for those with heart disease aged <65 years and £4,356 for those with heart disease to £4,751 for those with liver disease aged >65 years who comprised 74.3% of admissions overall., Conclusion: This estimate of the cost of hospitalization for CAP from the total population and in those with certain underlying comorbidities will allow a valid understanding of the cost-benefit of vaccination and evidence-based prioritization of pneumococcal vaccination to those at highest risk.

Background: Despite progress in TB control in low-burden countries like England and Wales, there are still diagnostic delays. Molecular testing and/or whole-genome sequencing (WGS) provide more rapid diagnosis but their cost-effectiveness is relatively unexplored in low-burden settings., Methods: An integrated transmission-dynamic health economic model is used to assess the cost-effectiveness of using WGS to replace culture-based drug-sensitivity testing, versus using molecular testing versus combined use of WGS and molecular testing, for routine TB diagnosis. The model accounts for the effects of faster appropriate treatment in reducing transmission, benefiting health and reducing future treatment costs. Cost-effectiveness is assessed using incremental net benefit (INB) over a 10-year horizon with a quality-adjusted life-year valued at £20 000, and discounting at 3.5% per year., Results: WGS shortens the time to drug sensitivity testing and treatment modification where necessary, reducing treatment and hospitalisation costs, with an INB of £7.1 million. Molecular testing shortens the time to TB diagnosis and treatment. Initially, this causes an increase in annual costs of treatment, but averting transmissions and future active TB disease subsequently, resulting in cost savings and health benefits to achieve an INB of £8.6 million (GeneXpert MTB/RIF) or £11.1 million (Xpert-Ultra). Combined use of Xpert-Ultra and WGS is the optimal strategy we consider, with an INB of £16.5 million., Conclusion: Routine use of WGS or molecular testing is cost-effective in a low-burden setting, and combined use is the most cost-effective option. Adoption of these technologies can help low-burden countries meet the WHO End TB Strategy milestones, particularly the UK, which still has relatively high TB rates., Competing Interests: Competing interests: None declared., (© 2021. No commercial re-use of BMJ published versions. See rights and permissions. Published by BMJ.)

Homeless persons have elevated risk of tuberculosis (TB) and are under-served by conventional health services. Approaches to active case-finding (ACF) and treatment tailored to their needs are required. A transmission-dynamic model was developed to assess the effectiveness and efficiency of screening with mobile Chest X-ray, GeneXpert, or both. Effectiveness of ACF depends upon the prevalence of infection in the population (which determines screening 'yield'), patient willingness to wait for GeneXpert results, and treatment adherence. ACF is efficient when TB prevalence exceeds 78/100,000 and 46% of drug sensitive TB cases and 33% of multi-drug resistant TB cases complete treatment. This threshold increases to 92/100,000 if additional post-ACF enhanced case management (ECM) increases treatment completion to 85%. Generally, the most efficient option is one-step screening of all patients with GeneXpert, but if too many patients (>27% without ECM, >19% with ECM) are unwilling to wait the 90 minutes required then two-step screening using chest X-ray (which is rapid) followed by GeneXpert for confirmation of TB is the most efficient option. Targeted ACF and support services benefit health through early successful treatment and averting TB transmission and disease. The optimal strategy is setting-specific, requiring careful consideration of patients' needs regarding testing and treatment.

The peripheral naive T-cell pool is generally thought to consist of a subpopulation of recent thymic emigrants (RTEs) and a subpopulation of mature naive (MN) T cells with different dynamics. Thymus transplantation and adoptive transfer studies in mice have provided contradicting results, with some studies suggesting that RTEs are relatively short-lived cells, while another study suggested that RTEs have a survival advantage. We here estimate the death rates of RTE and MN T cells by performing both thymus transplantations and deuterium labeling experiments in mice of at least 12 weeks old, an age at which the size of the T-cell pool has stabilized. For CD4 + T cells, we found the total loss rate from the RTE compartment (by death and maturation) to be fourfold faster than that of MN T cells. We estimate the death rate of CD4 + RTE to be 0.046 per day, which is threefold faster than the total loss rate from the MN T-cell compartment. For CD8 + T cells, we found no evidence for kinetic differences between RTE and MN T cells. Thus, our data support the notion that in young adult mice, CD4 + RTE are relatively short-lived cells within the naive CD4 + T-cell pool.

Naive T cells in untreated HIV-1 infected individuals have a reduced T-cell receptor excision circle (TREC) content. Previous mathematical models have suggested that this is due to increased naive T-cell division. It remains unclear, however, how reduced naive TREC contents can be reconciled with a gradual loss of naive T cells in HIV-1 infection. We performed longitudinal analyses in humans before and after HIV-1 seroconversion, and used a mathematical model to investigate which processes could explain the observed changes in naive T-cell numbers and TRECs during untreated HIV-1 disease progression. Both CD4+ and CD8+ naive T-cell TREC contents declined biphasically, with a rapid loss during the first year and a much slower loss during the chronic phase of infection. While naive CD8+ T-cell numbers hardly changed during follow-up, naive CD4+ T-cell counts continually declined. We show that a fine balance between increased T-cell division and loss in the peripheral naive T-cell pool can explain the observed short- and long-term changes in TRECs and naive T-cell numbers, especially if T-cell turnover during the acute phase is more increased than during the chronic phase of infection. Loss of thymic output, on the other hand, does not help to explain the biphasic loss of TRECs in HIV infection. The observed longitudinal changes in TRECs and naive T-cell numbers in HIV-infected individuals are most likely explained by a tight balance between increased T-cell division and death, suggesting that these changes are intrinsically linked in HIV infection.

Aims: Nirmatrelvir/ritonavir (NMV/r) is an orally administered antiviral indicated for the outpatient treatment of adult patients with mild-to-moderate COVID-19 at high risk for disease progression to severe illness. We estimated the cost-effectiveness of NMV/r versus best supportive care for 54 patient cohorts, specified according to age, vaccination status and comorbidity burden., Materials and Methods: A previously published and validated cost-effectiveness model was utilized and adapted to the Swedish setting. The model used a short-term decision-tree (1 year) followed by a lifetime 2-state Markov model. The short-term decision-tree captured costs and outcomes associated with the primary infection. Post-acute COVID-19 syndrome was only considered in terms of quality-of-life decrements for one year. Baseline hospitalization and mortality risks were taken from a Swedish, nationwide, uniquely granular, Omicron-era, real-world study. NMV/r effectiveness were taken from an Omicron-era US real-world study. Remaining inputs were informed by previous COVID-19 studies and publicly available Swedish sources., Results: The incremental cost-effectiveness ratios (ICERs) showed a large variation ranging from almost nine million SEK for some of the youngest cohorts to being dominant (i.e. cost-saving with higher gains in quality-of-life vs standard of care) for twelve elderly cohorts. In general, higher age in combination with non-recent (>180 days) or no vaccination led to lower ICERs. Specifically, NMV/r was cost-effective for all but one patient cohorts at least 70 years old, and for most patient cohorts 60-69 years old., Limitations: As the COVID-19 landscape changes, symptom burden and baseline risks constantly change. Thus, the cost-effectiveness of NMV/r will change with time. However, the future risks could be related to the risks in the current study, and thus remain useful for decision makers., Conclusions: This study shows that NMV/r is a cost-effective or even cost-saving treatment option for many patient cohorts, including most elderly and not-recently vaccinated patients with at least some comorbidity burden.

Background: In HIV infection, the homeostasis of CD4 and CD8 T cells is dramatically disturbed, and several studies have pointed out that T-cell turnover rates are increased. To understand how the CD4 and CD8 T-cell pools are affected, it is important to have quantitative insights into the lifespans of the cells constituting the different T-lymphocyte populations., Methods: We used long-term in-vivo H2O labeling and mathematical modeling to estimate the average lifespans of naive and memory CD4 and CD8 T cells in untreated (n = 4) and combination antiretroviral therapy-treated (n = 3) HIV-1-infected individuals., Results: During untreated chronic HIV-1 infection, naive CD4 and CD8 T cells lived on average 618 and 271 days, whereas memory CD4 and CD8 T cells had average lifespans of 53 and 43 days, respectively. These lifespans were at least three-fold shorter than those in healthy controls (n = 5). In patients on effective combination antiretroviral therapy with total CD4 T-cell counts in the normal range, we found that naive CD4 and CD8 T-cell lifespans had not completely normalized and were still two-fold shortened., Conclusion: The average lifespan of both naive and memory CD4 and CD8 T cells decreased during untreated chronic HIV-1 infection. Although the turnover of the memory T-cell populations nearly normalized during effective treatment, the turnover of naive CD4 and CD8 T cells did not seem to normalize completely.

Background: Drug-resistant tuberculosis (TB), especially multidrug-resistant (MDR, resistance to rifampicin and isoniazid) disease, is associated with a worse patient outcome. Drug resistance diagnosed using microbiological culture takes days to weeks, as TB bacteria grow slowly. Rapid molecular tests for drug resistance detection (1 day) are commercially available and may promote faster initiation of appropriate treatment., Objectives: To (1) conduct a systematic review of evidence regarding diagnostic accuracy of molecular genetic tests for drug resistance, (2) conduct a health-economic evaluation of screening and diagnostic strategies, including comparison of alternative models of service provision and assessment of the value of targeting rapid testing at high-risk subgroups, and (3) construct a transmission-dynamic mathematical model that translates the estimates of diagnostic accuracy into estimates of clinical impact., Review Methods and Data Sources: A standardised search strategy identified relevant studies from EMBASE, PubMed, MEDLINE, Bioscience Information Service (BIOSIS), System for Information on Grey Literature in Europe Social Policy & Practice (SIGLE) and Web of Science, published between 1 January 2000 and 15 August 2013. Additional 'grey' sources were included. Quality was assessed using quality assessment of diagnostic accuracy studies version 2 (QUADAS-2). For each diagnostic strategy and population subgroup, a care pathway was constructed to specify which medical treatments and health services that individuals would receive from presentation to the point where they either did or did not complete TB treatment successfully. A total cost was estimated from a health service perspective for each care pathway, and the health impact was estimated in terms of the mean discounted quality-adjusted life-years (QALYs) lost as a result of disease and treatment. Costs and QALYs were both discounted at 3.5% per year. An integrated transmission-dynamic and economic model was used to evaluate the cost-effectiveness of introducing rapid molecular testing (in addition to culture and drug sensitivity testing). Probabilistic sensitivity analysis was performed to evaluate the impact on cost-effectiveness of diagnostic and treatment time delays, diagnosis and treatment costs, and associated QALYs., Results: A total of 8922 titles and abstracts were identified, with 557 papers being potentially eligible. Of these, 56 studies contained sufficient test information for analysis. All three commercial tests performed well when detecting drug resistance in clinical samples, although with evidence of heterogeneity between studies. Pooled sensitivity for GenoType® MTBDRplus (Hain Lifescience, Nehren, Germany) (isoniazid and rifampicin resistance), INNO-LiPA Rif.TB® (Fujirebio Europe, Ghent, Belgium) (rifampicin resistance) and Xpert® MTB/RIF (Cepheid Inc., Sunnyvale, CA, USA) (rifampicin resistance) was 83.4%, 94.6%, 95.4% and 96.8%, respectively; equivalent pooled specificity was 99.6%, 98.2%, 99.7% and 98.4%, respectively. Results of the transmission model suggest that all of the rapid assays considered here, if added to the current diagnostic pathway, would be cost-saving and achieve a reduction in expected QALY loss compared with current practice. GenoType MTBDRplus appeared to be the most cost-effective of the rapid tests in the South Asian population, although results were similar for GeneXpert. In all other scenarios GeneXpert appeared to be the most cost-effective strategy., Conclusions: Rapid molecular tests for rifampicin and isoniazid resistance were sensitive and specific. They may also be cost-effective when added to culture drug susceptibility testing in the UK. There is global interest in point-of-care testing and further work is needed to review the performance of emerging tests and the wider health-economic impact of decentralised testing in clinics and primary care, as well as non-health-care settings, such as shelters and prisons., Study Registration: This study is registered as PROSPERO CRD42011001537., Funding: The National Institute for Health Research Health Technology Assessment programme.

Quantitative knowledge of the turnover of different leukocyte populations is a key to our understanding of immune function in health and disease. Much progress has been made thanks to the introduction of stable isotope labeling, the state-of-the-art technique for in vivo quantification of cellular life spans. Yet, even leukocyte life span estimates on the basis of stable isotope labeling can vary up to 10-fold among laboratories. We investigated whether these differences could be the result of variances in the length of the labeling period among studies. To this end, we performed deuterated water-labeling experiments in mice, in which only the length of label administration was varied. The resulting life span estimates were indeed dependent on the length of the labeling period when the data were analyzed using a commonly used single-exponential model. We show that multiexponential models provide the necessary tool to obtain life span estimates that are independent of the length of the labeling period. Use of a multiexponential model enabled us to reduce the gap between human T-cell life span estimates from 2 previously published labeling studies. This provides an important step toward unambiguous understanding of leukocyte turnover in health and disease.

Parallels between T cell kinetics in mice and men have fueled the idea that a young mouse is a good model system for a young human, and an old mouse, for an elderly human. By combining in vivo kinetic labeling using deuterated water, thymectomy experiments, analysis of T cell receptor excision circles and CD31 expression, and mathematical modeling, we have quantified the contribution of thymus output and peripheral naive T cell division to the maintenance of T cells in mice and men. Aging affected naive T cell maintenance fundamentally differently in mice and men. Whereas the naive T cell pool in mice was almost exclusively sustained by thymus output throughout their lifetime, the maintenance of the adult human naive T cell pool occurred almost exclusively through peripheral T cell division. These findings put constraints on the extrapolation of insights into T cell dynamics from mouse to man and vice versa., (Copyright © 2012 Elsevier Inc. All rights reserved.)