Browsing by Author "Keiser, Olivia"

Now showing 1 - 7 of 7
  • Thumbnail Image
    Item
    Open Access
    The cost-effectiveness of monitoring strategies for antiretroviral therapy of HIV infected patients in resource-limited settings: software tool
    (Public Library of Science, 2015) Estill, Janne; Salazar-Vizcaya, Luisa; Blaser, Nello; Egger, Matthias; Keiser, Olivia
    BACKGROUND: The cost-effectiveness of routine viral load (VL) monitoring of HIV-infected patients on antiretroviral therapy (ART) depends on various factors that differ between settings and across time. Low-cost point-of-care (POC) tests for VL are in development and may make routine VL monitoring affordable in resource-limited settings. We developed a software tool to study the cost-effectiveness of switching to second-line ART with different monitoring strategies, and focused on POC-VL monitoring. METHODS: We used a mathematical model to simulate cohorts of patients from start of ART until death. We modeled 13 strategies (no 2 nd -line, clinical, CD4 (with or without targeted VL), POC-VL, and laboratory-based VL monitoring, with different frequencies). We included a scenario with identical failure rates across strategies, and one in which routine VL monitoring reduces the risk of failure. We compared lifetime costs and averted disability-adjusted life-years (DALYs). We calculated incremental cost-effectiveness ratios (ICER). We developed an Excel tool to update the results of the model for varying unit costs and cohort characteristics, and conducted several sensitivity analyses varying the input costs. RESULTS: Introducing 2 nd -line ART had an ICER of US$1651-1766/DALY averted. Compared with clinical monitoring, the ICER of CD4 monitoring was US$1896-US$5488/DALY averted and VL monitoring US$951-US$5813/DALY averted. We found no difference between POC- and laboratory-based VL monitoring, except for the highest measurement frequency (every 6 months), where laboratory-based testing was more effective. Targeted VL monitoring was on the cost-effectiveness frontier only if the difference between 1 st - and 2 nd -line costs remained large, and if we assumed that routine VL monitoring does not prevent failure. CONCLUSION: Compared with the less expensive strategies, the cost-effectiveness of routine VL monitoring essentially depends on the cost of 2 nd -line ART. Our Excel tool is useful for determining optimal monitoring strategies for specific settings, with specific sex-and age-distributions and unit costs.
  • Thumbnail Image
    Item
    Open Access
    Estimating loss to follow-up in HIV-infected patients on antiretroviral therapy: the effect of the competing risk of death in Zambia and Switzerland
    (Public Library of Science, 2011) Schöni-Affolter, Franziska; Keiser, Olivia; Mwango, Albert; Stringer, Jeffrey; Ledergerber, Bruno; Mulenga, Lloyd; Bucher, Heiner C; Westfall, Andrew O; Calmy, Alexandra; Boulle, Andrew; Chintu, Namwinga; Egger, Matthias; Chi, Benjamin H
    BACKGROUND: Loss to follow-up (LTFU) is common in antiretroviral therapy (ART) programmes. Mortality is a competing risk (CR) for LTFU; however, it is often overlooked in cohort analyses. We examined how the CR of death affected LTFU estimates in Zambia and Switzerland. Methods and FINDINGS: HIV-infected patients aged ≥18 years who started ART 2004-2008 in observational cohorts in Zambia and Switzerland were included. We compared standard Kaplan-Meier curves with CR cumulative incidence. We calculated hazard ratios for LTFU across CD4 cell count strata using cause-specific Cox models, or Fine and Gray subdistribution models, adjusting for age, gender, body mass index and clinical stage. 89,339 patients from Zambia and 1,860 patients from Switzerland were included. 12,237 patients (13.7%) in Zambia and 129 patients (6.9%) in Switzerland were LTFU and 8,498 (9.5%) and 29 patients (1.6%), respectively, died. In Zambia, the probability of LTFU was overestimated in Kaplan-Meier curves: estimates at 3.5 years were 29.3% for patients starting ART with CD4 cells <100 cells/µl and 15.4% among patients starting with ≥350 cells/µL. The estimates from CR cumulative incidence were 22.9% and 13.6%, respectively. Little difference was found between naïve and CR analyses in Switzerland since only few patients died. The results from Cox and Fine and Gray models were similar: in Zambia the risk of loss to follow-up and death increased with decreasing CD4 counts at the start of ART, whereas in Switzerland there was a trend in the opposite direction, with patients with higher CD4 cell counts more likely to be lost to follow-up. CONCLUSIONS: In ART programmes in low-income settings the competing risk of death can substantially bias standard analyses of LTFU. The CD4 cell count and other prognostic factors may be differentially associated with LTFU in low-income and high-income settings.
  • Thumbnail Image
    Item
    Open Access
    Growth of HIV-exposed uninfected infants in the first 6 months of life in South Africa: The IeDEA-SA collaboration
    (Public Library of Science, 2016) Morden, Erna; Technau, Karl-Günter; Giddy, Janet; Maxwell, Nicola; Keiser, Olivia; Davies, Mary-Ann
    BACKGROUND: HIV-exposed uninfected (HEU) infants are a growing population in sub-Saharan Africa especially with the increasing coverage of more effective prevention of mother-to-child transmission (PMTCT) antiretroviral therapy regimens. This study describes the characteristics of South African HEU infants, investigates factors impacting birth weight and assesses their growth within the first 28 weeks of life. METHODS: This is a retrospective cohort based on routine clinical data from two South African PMTCT programmes. Data were collected between 2007 and 2013. Linear regression assessed factors affecting birth weight-for-age z-scores (WAZ) while growth (longitudinal WAZ) was assessed using mixed effects models. RESULTS: We assessed the growth of 2621 HEU infants (median birth WAZ was -0.65 (IQR -1.46; 0.0) and 51% were male). The feeding modalities practised were as follows: 0.5% exclusive breastfeeding, 7.9% breastfeeding with unknown exclusivity, 0.08% mixed breastfeeding and 89.2% formula feeding. Mothers with CD4 <200 cells/μl delivered infants with a lower birth WAZ (adjusted ß -0.253 [95% CI -0.043; -0.072], p = 0.006) compared to mothers with aCD4 ≥500 cells/μl. Similarly, mothers who did not receive antiretroviral drugs delivered infants with a lower birth WAZ (adjusted ß -0.39 [95% CI -0.67; -0.11], p = 0.007) compared to mothers who received antenatal antiretrovirals. Infants with a birth weight <2 500g (ß 0.070 [95% CI 0.061; 0.078], p <0.0001) experienced faster growth within the first 28 weeks of life compared to infants with a birth weight ≥2 500g. Infants with any breastfeeding exposure experienced slower longitudinal growth compared to formula fed infants (adjusted ß -0.012 [95% CI 0.021; -0.003], p = 0.011). CONCLUSION: Less severe maternal disease and the use of antiretrovirals positively impacts birth weight in this cohort of South African HEU infants. Formula feeding was common with breastfed infants experiencing marginally slower longitudinal growth.
  • Thumbnail Image
    Item
    Restricted
    Long-term immunologic response to antiretroviral therapy in low-income countries: a collaborative analysis of prospective studies
    (Lippincott, Williams & Wilkins, 2008) Nash, Denis; Katyal, Monica; Brinkhof, Martin W G; Keiser, Olivia; May, Margaret; Hughes, Rachael; Dabis, Francois; Wood, Robin; Sprinz, Eduardo; Schechter, Mauro; Egger, Matthias
    Background: Few data are available on the long-term immunologic response to ART in resource-limited settings, where antiretroviral therapy (ART) is being scaled up using a public health approach, with a limited repertoire of drugs. Objectives: To describe immunologic response to ART in a network of cohorts from sub-Saharan Africa, Latin America, and Asia. Study population/methodsL: Treatment-naïve patients aged 15 and older from 27 treatment programs were eligible. Multi-level, linear mixed models were used to assess associations between predictor variables and CD4 count trajectories following ART initiation. Results: Of 29,175 patients initiating ART, 8,933 patients (31%) were excluded due to insufficient follow-up time and early lost to follow-up or death. The remaining 19,967 patients contributed 39,200 person-years on ART and 71,067 CD4 measurements. The median baseline CD4 count was 114 cells/μL, with 35%<100 cells μL and substantial inter-site variation (range: 61-181 cells/μL). Females had higher median baseline CD4 counts than males (121 vs. 104 cells/μL). The median CD4 count increased from 114 cells/μL at ART initiation to 230 (IQR:144-338) at 6 months, 263 (IQR:175-376) at 1 year, 336 (IQR:224-472) at 2 years, 372 (IQR:242-537) at 3 years, 377 (IQR:221-561) at 4 years, and 395 (IQR:240-592) at 5 years. In multivariable models, baseline CD4 count was the most important determinant of subsequent CD4 count trajectories. Conclusions: These data demonstrate robust and sustained CD4 response to ART among patients remaining on therapy. Public health and programmatic interventions leading to earlier HIV diagnosis and initiation of ART could substantially improve patient outcomes in resource-limited settings.
  • Thumbnail Image
    Item
    Open Access
    Mortality in patients with HIV-1 infection starting antiretroviral therapy in South Africa, Europe, or North America: a collaborative analysis of prospective studies
    (Public Library of Science, 2014) Boulle, Andrew; Schomaker, Michael; May, Margaret T; Hogg, Robert S; Shepherd, Bryan E; Monge, Susana; Keiser, Olivia; Lampe, Fiona C; Giddy, Janet; Ndirangu, James
    Analyzing survival in HIV treatment cohorts, Andrew Boulle and colleagues find mortality rates in South Africa comparable to or better than those in North America by 4 years after starting antiretroviral therapy. Please see later in the article for the Editors' Summary
  • Thumbnail Image
    Item
    Open Access
    Public-health and individual approaches to antiretroviral therapy: township South Africa and Switzerland compared
    (Public Library of Science, 2008) Keiser, Olivia; Orrell, Catherine; Egger, Matthias; Wood, Robin; Brinkhof, Martin W G; Furrer, Hansjakob; vCutsem, Gilles; Ledergerber, Bruno; Boulle, Andrew; (IeDEA-SA), for the Swiss HIV Cohort Study (SHCS) and the International Epidemiologic Databases
    Comparing HIV treatment in Switzerland, where drug selection is individualized, and South Africa, where a programmatic approach is used, Matthias Egger and colleagues find similar virologic outcomes over two years.
  • Thumbnail Image
    Item
    Open Access
    Retention in care of HIV-infected children from HIV test to start of antiretroviral therapy: systematic review
    (Public Library of Science, 2013) Mugglin, Catrina; Wandeler, Gilles; Estill, Janne; Egger, Matthias; Bender, Nicole; Davies, Mary-Ann; Keiser, Olivia
    BACKGROUND: In adults it is well documented that there are substantial losses to the programme between HIV testing and start of antiretroviral therapy (ART). The magnitude and reasons for loss to follow-up and death between HIV diagnosis and start of ART in children are not well defined. METHODS: We searched the PubMed and EMBASE databases for studies on children followed between HIV diagnosis and start of ART in low-income settings. We examined the proportion of children with a CD4 cell count/percentage after after being diagnosed with HIV infection, the number of treatment-eligible children starting ART and predictors of loss to programme. Data were extracted in duplicate. RESULTS: Eight studies from sub-Saharan Africa and two studies from Asia with a total of 10,741 children were included. Median age ranged from 2.2 to 6.5 years. Between 78.0 and 97.0% of HIV-infected children subsequently had a CD4 cell count/percentage measured, 63.2 to 90.7% of children with an eligibility assessment met the eligibility criteria for the particular setting and time and 39.5 to 99.4% of the eligible children started ART. Three studies reported an association between low CD4 count/percentage and ART initiation while no association was reported for gender. Only two studies reported on pre-ART mortality and found rates of 13 and 6 per 100 person-years. CONCLUSION: Most children who presented for HIV care met eligibility criteria for ART. There is an urgent need for strategies to improve the access to and retention to care of HIV-infected children in resource-limited settings.