CD4 cell count as a surrogate endpoint in HIV clinical trials: a meta-analysis of studies of the AIDS Clinical Trials Group

Integrating biology into clinical trial design

PURPOSE OF REVIEW

Critical care medicine revolves around syndromes, such as acute respiratory distress syndrome (ARDS), sepsis and acute kidney injury. Few interventions have shown to be effective in large clinical trials, likely because of between-patient heterogeneity. Translational evidence suggests that more homogeneous biological subgroups can be identified and that differential treatment effects exist. Integrating biological considerations into clinical trial design is therefore an important frontier of critical care research.

RECENT FINDINGS

The pathophysiology of critical care syndromes involves a multiplicity of processes, which emphasizes the difficulty of integrating biology into clinical trial design. Biological assessment can be integrated into clinical trials using predictive enrichment at trial inclusion, time-dependent variation to better understand treatment effects and biological markers as surrogate outcomes.

SUMMARY

Integrating our knowledge on biological heterogeneity into clinical trial design, which has revolutionized other medical fields, could serve as a solution to implement personalized treatment in critical care syndromes. Changing the trial design by using predictive enrichment, incorporation of the evaluation of time-dependent changes and biological markers as surrogate outcomes may improve the likelihood of detecting a beneficial effect from targeted therapeutic interventions and the opportunity to test multiple lines of treatment per patient.

Quantifying direct and indirect effect for longitudinal mediator and survival outcome using joint modeling approach

Longitudinal biomarkers are widely used in biomedical and translational researches to monitor the progressions of diseases. Methods have been proposed to jointly model longitudinal data and survival data, but its causal mechanism is yet to be investigated rigorously. Understanding how much of the total treatment effect is through the biomarker is important in understanding the treatment mechanism and evaluating the biomarker. In this work, we propose a causal mediation analysis method to compute the direct and indirect effects, when a joint modeling approach is used to take the longitudinal biomarker as the mediator and the survival endpoint as the outcome. Such a joint modeling approach allows us to relax the commonly used "sequential ignorability" assumption. We demonstrate how to evaluate longitudinally measured biomarkers using our method with two case studies, an AIDS study and a liver cirrhosis study.

Do-calculus enables estimation of causal effects in partially observed biomolecular pathways

MOTIVATION

Estimating causal queries, such as changes in protein abundance in response to a perturbation, is a fundamental task in the analysis of biomolecular pathways. The estimation requires experimental measurements on the pathway components. However, in practice many pathway components are left unobserved (latent) because they are either unknown, or difficult to measure. Latent variable models (LVMs) are well-suited for such estimation. Unfortunately, LVM-based estimation of causal queries can be inaccurate when parameters of the latent variables are not uniquely identified, or when the number of latent variables is misspecified. This has limited the use of LVMs for causal inference in biomolecular pathways.

RESULTS

In this article, we propose a general and practical approach for LVM-based estimation of causal queries. We prove that, despite the challenges above, LVM-based estimators of causal queries are accurate if the queries are identifiable according to Pearl's do-calculus and describe an algorithm for its estimation. We illustrate the breadth and the practical utility of this approach for estimating causal queries in four synthetic and two experimental case studies, where structures of biomolecular pathways challenge the existing methods for causal query estimation.

AVAILABILITY AND IMPLEMENTATION

The code and the data documenting all the case studies are available at https://github.com/srtaheri/LVMwithDoCalculus.

SUPPLEMENTARY INFORMATION

Supplementary data are available at Bioinformatics online.

Surrogate Endpoints in Health Technology Assessment: An International Review of Methodological Guidelines

In the drive towards faster patient access to treatments, health technology assessment (HTA) agencies are increasingly faced with reliance on evidence from surrogate endpoints, leading to increased decision uncertainty. This study undertook an updated survey of methodological guidance for using surrogate endpoints across international HTA agencies. We reviewed HTA and economic evaluation methods guidance from European, Australian and Canadian HTA agencies. We considered how guidelines addressed the methods for handling surrogate endpoints, including (1) level of evidence, (2) methods of validation, and (3) thresholds of acceptability. Across the 73 HTA agencies surveyed, 29 (40%) had methodological guidelines that made specific reference to consideration of surrogate outcomes. Of the 45 methods documents analysed, the majority [27 (60%)] were non-technology specific, 15 (33%) focused on pharmaceuticals and three (7%) on medical devices. The principles of the European network for Health Technology Assessment (EUnetHTA) guidelines published in 2015 on the handling of surrogate endpoints appear to have been adopted by many European HTA agencies, i.e. preference for final patient-relevant outcomes and reliance on surrogate endpoints with biological plausibility and epidemiological evidence of the association between the surrogate and final endpoint. Only a small number of HTA agencies (UK National Institute for Care and Excellence; the German Institute for Medical Documentation and Information and Institute for Quality and Efficiency in Health Care; the Australian Pharmaceutical Benefits Advisory Committee; and the Canadian Agency for Drugs and Technologies in Health) have developed more detailed prescriptive criteria for the acceptance of surrogate endpoints, e.g. meta-analyses of randomised controlled trials showing strong association between the treatment effect on the surrogate and final outcomes. As the decision uncertainty associated with reliance on surrogate endpoints carries a risk to patients and society, there is a need for HTA agencies to develop more detailed methodological guidance for consistent selection and evaluation of health technologies that lack definitive final patient-relevant outcome evidence at the time of the assessment.

Assessing the value of a censored surrogate outcome

Assessing the potential of surrogate markers and surrogate outcomes for replacing a long term outcome is an active area of research. The interest in this topic is partly motivated by increasing pressure from stakeholders to shorten the time required to evaluate the safety and/or efficacy of a treatment or intervention such that treatments deemed safe and effective can be made available to those in need more quickly. Most existing methods in surrogacy evaluation either require strict model assumptions or that primary outcome and surrogate outcome information is available for all study participants. In this paper, we focus on a setting where the primary outcome is subject to censoring and the aim is to quantify the surrogacy of an intermediate outcome, which is also subject to censoring. We define the surrogacy as the proportion of treatment effect on the primary outcome that is explained by the intermediate surrogate outcome information and propose two robust methods to estimate this quantity. We propose both a nonparametric approach that uses a kernel smoothed Nelson-Aalen estimator of conditional survival, and a semiparametric method that derives conditional survival estimates from a landmark Cox proportional hazards model. Simulation studies demonstrate that both approaches perform well in finite samples. Our methodological development is motivated by our interest in investigating the use of a composite cardiovascular endpoint as a surrogate outcome in a randomized study of the effectiveness of angiotensin-converting enzyme inhibitors on survival. We apply the proposed methods to quantify the surrogacy of this potential surrogate outcome for the primary outcome, time to death.

Exploring causality mechanism in the joint analysis of longitudinal and survival data

In many biomedical studies, disease progress is monitored by a biomarker over time, eg, repeated measures of CD4 in AIDS and hemoglobin in end-stage renal disease patients. The endpoint of interest, eg, death or diagnosis of a specific disease, is correlated with the longitudinal biomarker. In this paper, we examine and compare different models of longitudinal and survival data to investigate causal mechanisms, specifically, those related to the role of random effects. We illustrate the methods by data from two clinical trials: an AIDS study and a liver cirrhosis study.

Biomarkers and Surrogate Endpoints: Lessons Learned From Glaucoma

With the recent progress in imaging technologies for assessment of structural damage in glaucoma, a debate has emerged on whether these measurements can be used as valid surrogate endpoints in clinical trials evaluating new therapies for the disease. A discussion of surrogates should be grounded on knowledge acquired from their use in other areas of medicine as well as regulatory requirements. This article reviews the conditions for valid surrogacy in the context of glaucoma clinical trials and critically evaluates the role of biomarkers such as IOP and imaging measurements as potential surrogates for clinically relevant outcomes. Valid surrogate endpoints must be able to predict a clinically relevant endpoint, such as loss of vision or decrease in quality of life. In addition, the effect of a proposed treatment on the surrogate must capture the effect of the treatment on the clinically relevant endpoint. Despite its widespread use in clinical trials, no proper validation of IOP as a surrogate endpoint has yet been conducted for any class of IOP-lowering treatments. Although strong evidence has accumulated about imaging measurements as predictors of relevant functional outcomes in glaucoma, there is still insufficient evidence to support their use as valid surrogate endpoints. However, imaging biomarkers could potentially be used as part of composite endpoints in glaucoma trials, overcoming weaknesses of the use of structural or functional endpoints in isolation. Efforts should be taken to properly design and conduct studies that can provide proper validation of potential biomarkers in glaucoma clinical trials.

Choice of first-line antiretroviral therapy regimen and treatment outcomes for HIV in a middle income compared to a high income country: a cohort study

Background

The range of combination antiretroviral therapy (cART) regimens available in many middle-income countries differs from those suggested in international HIV treatment guidelines. We compared first-line cART regimens, timing of initiation and treatment outcomes in a middle income setting (HIV Centre, Belgrade, Serbia - HCB) with a high-income country (Royal Free London Hospital, UK - RFH).

Methods

All antiretroviral-naïve HIV-positive individuals from HCB and RFH starting cART between 2003 and 2012 were included. 12-month viral load and CD4 count responses were compared, considering the first available measurement 12-24 months post-cART. The percentage that had made an antiretroviral switch for any reason, or for toxicity and the percentage that had died by 36 months (the latest time at which sufficient numbers remained under follow-up) were investigated using standard survival methods.

Results

361/597 (61 %) of individuals initiating cART at HCB had a prior AIDS diagnosis, compared to 337/1763 (19 %) at RFH. Median pre-ART CD4 counts were 177 and 238 cells/mm³ respectively (p < 0.0001). The most frequently prescribed antiretrovirals were zidovudine with lamivudine (149; 25 %) and efavirenz [329, 55 %] at HCB and emtricitabine with tenofovir (899; 51 %) and efavirenz [681, 39 %] at RFH. At HCB, a median of 2 CD4 count measurements in the first year of cART were taken, compared to 5 at RFH (p < 0.0001). Median (IQR) CD4 cell increase after 12 months was +211 (+86, +359) and +212 (+105, +318) respectively. 287 (48 %) individuals from HCB and 1452 (82 %) from RFH had an available viral load measurement, of which 271 (94 %) and 1280 (88 %) were <400 copies/mL (p < 0.0001). After 36 months, comparable percentages had made at least one antiretroviral switch (77 % HCB vs. 78 % RFH; p = 0.23). However, switches for toxicity/patient choice were more common at RFH. After 12 and 36 months of cART 3 % and 8 % of individuals died at HCB, versus 2 % and 4 % at RFH (p < 0.0001).

Conclusion

In middle-income countries, cART is usually started at an advanced stage of HIV disease, resulting in higher mortality rates than in high income countries, supporting improved testing campaigns for early detection of HIV infection and early introduction of newer cART regimens.

CD4+ T cell counts in initiation of antiretroviral therapy in HIV infected asymptomatic individuals; controversies and inconsistencies

The primary goal when devising strategies to define the start of therapy in HIV infected individuals is to avoid HIV disease progression and toxicity from antiretroviral therapy (ART). Intermediate goals includes, avoiding resistance by suppressing HIV replication, reducing transmission, limiting spread and diversity of HIV within the body and protecting the immune system from harm. The question of how early or late to start ART and achieve both primary and intermediate goals has dominated HIV research. The distinction between early and late treatment of HIV infection is currently a matter of CD4+ T cells count, a marker of immune status, rather than on viral load, a marker of virus replication. Discussions about respective benefits of early or delayed therapy, as well as the best CD4+ T cell threshold during the course of HIV infection at which ART is initiated remains inconclusive. Guidelines issued by various agencies, provide different initiation recommendations. This can be confusing for clinicians and policy-makers when determining the best time to initiate therapy. Optimizing ART initiation strategies are clearly complex and must be balanced between individual and broader public health needs. This review assesses available data that contributes to the debate on optimal time to initiate therapy in HIV-infected asymptomatic individuals. We also review reports on CD4+ T cell threshold to guide initiation of ART and finally discuss arguments for and against early or late initiation of ART.

Alternative end points for trauma studies: A survey of academic trauma surgeons

INTRODUCTION

Changing the epidemiology of trauma makes traditional end points like 30-day mortality less than ideal. Many alternative end points have been suggested; however, they are not yet accepted by the trauma community or regulatory bodies. This study characterizes opinions about the adequacy of accepted end points of studies of trauma and the appropriateness of several novel end points.

METHODS

An electronic survey was administered to all members of the American Association for the Surgery of Trauma. Questions involved demographics, research experience, appropriateness of proposed study end points, and the role of nontraditional, surrogate, and composite end points.

RESULTS

Response rate was 16% (141 of 873) with 74% of respondents practicing at Level 1 Trauma Centers. The respondents were very experienced, with 81% reporting >10 years of practice at the attending level and 87% actively involved in research. The majority of respondents rated the following end points favorably: 24-hour survival, 30-day survival, and time to control of acute hemorrhage with approval rates of 82%, 78%, and 76%, respectively. Six-hour survival, intensive care unit-free survival, and days free of multiorgan failure were rated as appropriate or very appropriate less than 66% of the time. Only 45% of respondents judged the currently used end points of trauma to be appropriate. More than 80% respondents disagreed or strongly disagreed that there was no role for of surrogate or composite endpoints in research of trauma resuscitation.

CONCLUSION

There is strong interest in finding efficient end points in trauma research that are both specific and reflect the changing epidemiology of trauma death. The alternative end points of 24-hour survival and time to control of acute hemorrhage had similar approval rates to 30-day mortality.

CD4 trajectory adjusting for dropout among HIV-positive patients receiving combination antiretroviral therapy in an East African HIV care centre

OBJECTIVE

Estimates of CD4 response to antiretroviral therapy (ART) obtained by averaging data from patients in care, overestimate population CD4 response and treatment program effectiveness because they do not consider data from patients who are deceased or not in care. We use mathematical methods to assess and adjust for this bias based on patient characteristics.

DESIGN

We examined data from 25,261 HIV-positive patients from the East Africa IeDEA Consortium.

METHODS

We used inverse probability of censoring weighting (IPCW) to represent patients not in care by patients in care with similar characteristics. We address two questions: What would the median CD4 be "had everyone starting ART remained on observation?" and "were everyone starting ART maintained on treatment?"

RESULTS

Routine CD4 count estimates were higher than adjusted estimates even under the best-case scenario of maintaining all patients on treatment. Two years after starting ART, differences between estimates diverged from 30 cells/µL, assuming similar mortality and treatment access among dropouts as patients in care, to over 100 cells/µL assuming 20% lower survival and 50% lower treatment access among dropouts. When considering only patients in care, the proportion of patients with CD4 above 350 cells/µL was 50% adjusted to below 30% when accounting for patients not in care. One-year mortality diverged 6-14% from the naïve estimates depending on assumptions about access to care among lost patients.

CONCLUSIONS

Ignoring mortality and loss to care results in over-estimation of ART response for patients starting treatment and exaggerates the efficacy of treatment programs administering it.

Poor CD4 recovery and risk of subsequent progression to AIDS or death despite viral suppression in a South African cohort

INTRODUCTION

The prognostic role of CD4 response in the first six months of treatment in patients achieving early viral suppression during HIV treatment is unclear.

METHODS

This was a cohort study of HIV-positive adults initiating antiretroviral therapy (ART) between April 2004 and August 2007 who achieved viral suppression (<400 copies/ml) by six months on treatment in South Africa. Immunological response at six months was defined as: (1) absolute CD4 reached (<200 vs. ≥ 200 cells/ml); (2) absolute CD4 reached (0-49, 50-200 and ≥ 200 cells/ml); and (3) CD4 increase from ART initiation (<0, 0-49, 50-199 and ≥ 200 cells/ml). We used Cox regression models to determine the relationship between each definition and both new AIDS-defining condition and death.

RESULTS

A total of 4129 patients were eligible for analysis; 212 (5.1%) of those patients experienced a new AIDS-defining condition and 154 (3.7%) died. Smaller CD4 gains by six months were associated with higher hazards of progression to AIDS (CD4<50 vs. ≥ 200 cells/ml; adjusted hazard ratio (aHR): 2.6; 95% CI: 1.2-2.1) and death (aHR: 2.8; 95% CI: 1.4-5.7). A decrease in CD4 count since ART initiation through six months (aHR: 2.4; 95% CI: 1.2-4.9) and smaller CD4 count gains (0-49 cells/ml; aHR: 2.0; 95% CI: 1.2-3.4 and 50-199 cells/ml; aHR: 1.5; 95% CI: 0.9-2.2) were also associated with greater risk of progression to AIDS compared to an increase of ≥ 200 cells/ml. When we examined mortality differences by gender among this virally suppressed cohort, a higher proportion of males died compared to females, 4.7% versus 3.2%, p=0.01. However, in multivariable analysis, we did not observe any significant differences: aHR: 1.39; 95% CI: 0.98-1.95.

CONCLUSIONS

Patients on ART with poor CD4 recovery early in treatment are at greater risk of progression to new AIDS diagnosis or death despite viral suppression. Approaches to managing this sub-group of patients need further investigation.

Immuno-virological discordance and the risk of non-AIDS and AIDS events in a large observational cohort of HIV-patients in Europe

BACKGROUND

The impact of immunosuppression despite virological suppression (immuno-virological discordance, ID) on the risk of developing fatal and non-fatal AIDS/non-AIDS events is unclear and remains to be elucidated.

METHODS

Patients in EuroSIDA starting at least 1 new antiretroviral drug with CD4<350 cells/µl and viral load (VL)>500 copies/mL were followed-up from the first day of VL< = 50 copies/ml until a new fatal/non-fatal non-AIDS/AIDS event. Considered non-AIDS events included non-AIDS malignancies, pancreatitis, severe liver disease with hepatic encephalopathy (>grade 3), cardio- and cerebrovascular events, and end-stage renal disease. Patients were classified over time according to whether current CD4 count was above (non-ID) or below (ID) baseline level. Relative rates (RR) of events were calculated for ID vs. non-ID using adjusted Poisson regression models.

RESULTS

2,913 patients contributed 11,491 person-years for the analysis of non-AIDS. 241 pre-specified non-AIDS events (including 84 deaths) and 89 AIDS events (including 10 deaths) occurred. The RR of developing pre-specified non-AIDS events for ID vs. non-ID was 1.96 (95% CI 1.37-2.81, p<0.001) in unadjusted analysis and 1.43 (0.94-2.17, p = 0.095) after controlling for current CD4 count. ID was not associated with the risk of AIDS events (aRR 0.76, 95% CI 0.41-1.38, p = 0.361).

CONCLUSION

Compared to CD4 responders, patients with immuno-virological discordance may be at increased risk of developing non-AIDS events. Further studies are warranted to establish whether in patients with ID, strategies to directly modify CD4 count response may be needed besides the use of ART.

Study design issues in evaluating immune biomarkers

PURPOSE OF REVIEW

The dramatic increase in the number and type of immune biomarkers that can be measured, particularly those assessing immune activation, has led to numerous investigations in HIV-infected individuals to explore pathogenesis and to assess therapeutic interventions that aim to attenuate immune activation. An overview is provided on study designs and related statistical and operational issues relevant to these investigations.

RECENT FINDINGS

Cohort studies and nested case-control studies within these cohorts have identified multiple biomarkers that are associated with an increased risk of disease. Early-stage clinical trials of therapies to address these risks in HIV-infected individuals with viral suppression on antiretroviral therapy are a substantial focus of current HIV research.

SUMMARY

Appropriate study design is essential in biomarker research.

Dynamical models of biomarkers and clinical progression for personalized medicine: the HIV context

Mechanistic models, based on ordinary differential equation systems, can exhibit very good predictive abilities that will be useful to build treatment monitoring strategies. In this review, we present the potential and the limitations of such models for guiding treatment (monitoring and optimizing) in HIV-infected patients. In the context of antiretroviral therapy, several biological processes should be considered in addition to the interaction between viruses and the host immune system: the mechanisms of action of the drugs, their pharmacokinetics and pharmacodynamics, as well as the viral and host characteristics. Another important aspect to take into account is clinical progression, although its implementation in such modelling approaches is not easy. Finally, the control theory and the use of intrinsic properties of mechanistic models make them very relevant for dynamic treatment adaptation. Their implementation would nevertheless require their evaluation through clinical trials.

CD4 cell count and viral load-specific rates of AIDS, non-AIDS and deaths according to current antiretroviral use

BACKGROUND

CD4 cell count and viral loads are used in clinical trials as surrogate endpoints for assessing efficacy of newly available antiretrovirals. If antiretrovirals act through other pathways or increase the risk of disease this would not be identified prior to licensing. The aim of this study was to investigate the CD4 cell count and viral load-specific rates of fatal and nonfatal AIDS and non-AIDS events according to current antiretrovirals.

METHODS

Poisson regression was used to compare overall events (fatal or nonfatal AIDS, non-AIDS or death), AIDS events (fatal and nonfatal) or non-AIDS events (fatal or nonfatal) for specific nucleoside pairs and third drugs used with more than 1000 person-years of follow-up (PYFU) after 1 January 2001.

RESULTS

Nine thousand, eight hundred and one patients contributed 42372.5 PYFU, during which 1203 (437 AIDS and 766 non-AIDS) events occurred. After adjustment, there was weak evidence of a difference in the overall events rates between nucleoside pairs (global P-value = 0.084), and third drugs (global P-value = 0.031). As compared to zidovudine/lamivudine, patients taking abacavir/lamivudine [adjusted incidence rate ratio (aIRR) 1.22; 95% CI 0.99-1.49] and abacavir and one other nucleoside [aIRR 1.51; 95% CI 1.14-2.02] had an increased incidence of overall events. Comparing the third drugs, those taking unboosted atazanavir had an increased incidence of overall events compared with those taking efavirenz (aIRR 1.46; 95% CI 1.09-1.95).

CONCLUSION

There was little evidence of substantial differences between antiretrovirals in the incidence of clinical disease for a given CD4 cell count or viral load, suggesting there are unlikely to be major unidentified adverse effects of specific antiretrovirals.

Comparison of treatment effect sizes associated with surrogate and final patient relevant outcomes in randomised controlled trials: meta-epidemiological study

OBJECTIVE

To quantify and compare the treatment effect and risk of bias of trials reporting biomarkers or intermediate outcomes (surrogate outcomes) versus trials using final patient relevant primary outcomes.

DESIGN

Meta-epidemiological study.

DATA SOURCES

All randomised clinical trials published in 2005 and 2006 in six high impact medical journals: Annals of Internal Medicine, BMJ, Journal of the American Medical Association, Lancet, New England Journal of Medicine, and PLoS Medicine.

STUDY SELECTION

Two independent reviewers selected trials.

DATA EXTRACTION

Trial characteristics, risk of bias, and outcomes were recorded according to a predefined form. Two reviewers independently checked data extraction. The ratio of odds ratios was used to quantify the degree of difference in treatment effects between the trials using surrogate outcomes and those using patient relevant outcomes, also adjusted for trial characteristics. A ratio of odds ratios >1.0 implies that trials with surrogate outcomes report larger intervention effects than trials with patient relevant outcomes.

RESULTS

84 trials using surrogate outcomes and 101 using patient relevant outcomes were considered for analyses. Study characteristics of trials using surrogate outcomes and those using patient relevant outcomes were well balanced, except for median sample size (371 v 741) and single centre status (23% v 9%). Their risk of bias did not differ. Primary analysis showed trials reporting surrogate endpoints to have larger treatment effects (odds ratio 0.51, 95% confidence interval 0.42 to 0.60) than trials reporting patient relevant outcomes (0.76, 0.70 to 0.82), with an unadjusted ratio of odds ratios of 1.47 (1.07 to 2.01) and adjusted ratio of odds ratios of 1.46 (1.05 to 2.04). This result was consistent across sensitivity and secondary analyses.

CONCLUSIONS

Trials reporting surrogate primary outcomes are more likely to report larger treatment effects than trials reporting final patient relevant primary outcomes. This finding was not explained by differences in the risk of bias or characteristics of the two groups of trials.

The CD4 lymphocyte count and risk of clinical progression

PURPOSE OF REVIEW

The CD4 lymphocyte count was identified as a key predictor of risk of AIDS defining diseases almost 20 years ago, early in the HIV epidemic. Several issues concerning its use to predict AIDS have arisen since. These include the difference between short and long-term prediction, the use of CD4 percentage compared with absolute counts, the impact of antiretroviral therapy on the predictive value of the CD4 count, the role relative to other markers such as viral load, the derivation of scores to predict AIDS diseases, the use of CD4 count as a surrogate endpoint, the role of the CD4 count nadir compared with the current value and the differential ability to predict different AIDS diseases.

RECENT FINDINGS

All the above issues have been clarified further and this process has continued through 2004 and 2005. These developments are briefly described in this review.

SUMMARY

The CD4 count remains the strongest short-term predictor of risk of AIDS so far identified in both treated and untreated patients and should continue to be a mainstay of monitoring for both untreated and treated patients.

Factors predictive of 30-day postoperative mortality in HIV/AIDS patients in the era of highly active antiretroviral therapy

BACKGROUND

Factors that predict HIV (human immunodeficiency virus)/AIDS patient postoperative mortality have remained poorly defined.

OBJECTIVES

The primary objective of this study was to identify factors predictive of short-term, postoperative mortality in HIV/AIDS patients. The secondary objective of this study was to develop a scoring system that would predict short-term postoperative mortality in HIV/AIDS patients.

METHODS

We retrospectively reviewed all HIV/AIDS patients who underwent surgical procedures in British Columbia, Canada, between April 1995 and March 2002. The primary outcome evaluated was 30-day postoperative mortality. Demographic, clinical, and hospitalization-related data were obtained and utilized to predict outcomes using a logistic regression model.

RESULTS

A total of 2305 procedures were carried out on 1322 patients during the study period. Admissions were classified as urgent/emergent for 1311 procedures (57%) and the overall 30-day postoperative mortality was 9.5% (126 deaths). Urgent/emergent admission, older age, prior surgery, a CD4 cell count of ≤ 50 cells/mm, a hemoglobin level ≤ 120 g/L, and a white blood cell count >11 g/L within 90 days before the surgical procedure was predictive of an increased 30-day postoperative mortality in a multivariate model. Using these variables, we formulated the HIV Surgical Mortality Score (HSMS) to obtain the median-estimated probability of postoperative death.

CONCLUSIONS

For accurate preoperative mortality risk stratification for HIV/AIDS patients, we have found that several clinical and laboratory variables must be evaluated. If appropriately validated, our proposed HSMS could be utilized to estimate the probability of short-term postoperative death among HIV/AIDS patients.

Factors predicting discordant virological and immunological responses to antiretroviral therapy in HIV-1 clade C infected Zulu/Xhosa in South Africa

Factors predicting suboptimal CD4 cell recovery have been studied in HIV clade-B infected US and European populations. It is, however, uncertain to what extent these results are applicable to HIV clade-C infected African populations. Multivariate analysis using logistic regression and longitudinal analyses using mixed models were employed to assess the impact of age, gender, baseline CD4 cell count, hemoglobin, body mass index (BMI), tuberculosis and other opportunistic co-infections, and frequencies of regimen change on CD4 cell recovery at 12 and 30 months and on overtime change in CD4 cells among 442 virologically suppressed South Africans. Despite adequate virological response 37% (95% CI:32%–42%) and 83% (95% CI:79%–86%) of patients on antiretroviral therapy failed to restore CD4 cell counts ≥200 cells/mm³ after 12 and ≥500 cells/mm³ after 30 months, respectively, in this South African cohort. Critical risk factors for inadequate recovery were older age (p = 0.001) and nadir CD4 cell count at ART initiation (p<0.0001), while concurrent TB co-infection, BMI, baseline hemoglobin, gender and antiretroviral regimen were not significant risk factors. These data suggest that greater efforts are needed to identify and treat HAART-eligible patients prior to severe CD4 cell decline or achievement of advanced age.

Considerations for Endpoint Selection When Designing HIV Clinical Trials

Selecting the primary endpoint is one of the most important decisions in designing clinical trials. Many HIV trials are powered for surrogate markers, often virologic suppression. Among 49 recently published Phase 3 or higher randomized HIV trials only 14% were powered for clinical outcomes such as the progression to AIDS, death, or serious non-AIDS diseases. We provide two examples where interventions modified the targeted surrogate markers but failed to provide clinical benefit. We review the use of surrogate and clinical endpoints, discuss the composition of clinical endpoints, and the need for endpoint verification. In HIV-infected individuals with CD4 cell counts above 200 cells/mm(3) serious non-AIDS conditions such as cardiovascular, renal, hepatic diseases and cancer contribute substantially to morbidity and mortality. In this population clinical endpoint trials should be powered for non-AIDS morbidity along with AIDS.

Clinical outcome of HIV-infected patients with discordant virological and immunological response to antiretroviral therapy

BACKGROUND

A subgroup of human immunodeficiency virus type 1 (HIV-1)-infected patients with severe immunodeficiency show persistently low CD4+ cell counts despite sustained viral suppression. It is unclear whether this immuno-virological discordance translates into an increased risk for clinical events.

METHODS

Data analysis from a large multicenter cohort incorporating 14,433 HIV-1-infected patients in Germany. Treatment-naive patients beginning antiretroviral therapy (ART) with CD4+ cell counts <200 cells/μL who achieved complete and sustained viral suppression <50 copies/mL (n = 1318) were stratified according to the duration of immuno-virological discordance (failure to achieve a CD4+ cell count ≥200 cells/μL). Groups were compared by descriptive and Poisson statistics. The time-varying discordance status was analyzed in a multivariable Cox model.

RESULTS

During a total of 5038 person years of follow-up, 42 new AIDS events occurred. The incidence rate of new AIDS events was highest in the initial 6 months of complete viral suppression (immuno-virological discordance group, 55.06; 95% confidence interval [CI], 30.82-90.82; and immune responder group, 24.54; 95% CI, 10.59-48.35) and decreased significantly by 65% per year in patients with immuno-virological discordance (incidence risk ratio, 0.35; 95% CI, 0.14-0.92; P = .03). Immuno-virological discordance and prior AIDS diagnosis were independently associated with new AIDS events (hazard ratio, 3.10; 95% CI, 1.09-8.82; P = .03).

CONCLUSION

Compared with immune responders, patients with immuno-virological discordance seem to remain at increased risk for AIDS. Absolute risk is greatly reduced after the first 6 months of complete viral suppression.

Role of interleukin-2 in patients with HIV infection

Control of viral replication to below the level of quantification using combination antiretroviral therapy (ART) [cART] has led to a dramatic fall in mortality and morbidity from AIDS. However, despite the success of cART, it has become apparent that many patients do not achieve normalized CD4+ T-cell counts despite virological suppression to below the level of quantification (<50 copies/mL). Increasing data from cohort studies and limited data from clinical trials, such as the SMART study, have shown that higher CD4+ T-cell counts are associated with reductions in morbidity and mortality from both AIDS and serious non-AIDS (SNA) conditions, including cardiovascular disease. Enhancement of immune restoration over and above that achievable with ART alone, using a number of strategies including cytokine therapy, has been of interest for many years. The most studied cytokine in this setting is recombinant interleukin (IL)-2 (rIL-2). The purpose of this review is to describe the current status of rIL-2 as a therapeutic agent in the treatment of HIV-1 infection. The review focuses on the rationale underpinning the exploration of rIL-2 in HIV infection, summarizing the phase II and III findings of rIL-2 as an adjunctive therapy to ART and the phase II studies of rIL-2 as an antiretroviral-sparing agent. The phase II studies demonstrated the potential utility of continuous intravenous IL-2 and subsequently intermittent dosing with subcutaneous rIL-2 as a cytokine that could expand the CD4+ T-cell pool in HIV-1-infected patients without any significant detrimental effect on HIV viral load and with an acceptable adverse-effect profile. These data were utilized in designing the phase II studies of rIL-2 as an ART-sparing agent and, more importantly, the large phase III clinical endpoint studies of rIL-2 in HIV-1-infected adults, ESPRIT and SILCAAT. In the latter, subcutaneous rIL-2 was given intermittently (5 days of twice-daily dosing at 4.5-7.5 million international units per dose every 8 weeks) to HIV-1-infected adults receiving cART using an induction/maintenance strategy. Both studies explored the clinical benefit of intermittent subcutaneous rIL-2 with cART versus cART in HIV-infected adults with CD4+ T-cell counts > or = 300 cells/microL (ESPRIT study) and 50-299 cells/microL (SILCAAT study). Both studies showed that receipt of rIL-2 conferred no clinical benefit despite a significantly higher CD4+ T-cell count in the rIL-2 arms of both studies. Moreover, there was an excess of grade 4 clinical events in ESPRIT rIL-2 recipients. The results of the phase III clinical endpoint studies showed that rIL-2 has no place as a therapeutic agent in the treatment of HIV infection.

The effect of combined antiretroviral therapy on the overall mortality of HIV-infected individuals

OBJECTIVE

To estimate the effect of combined antiretroviral therapy (cART) on mortality among HIV-infected individuals after appropriate adjustment for time-varying confounding by indication.

DESIGN

A collaboration of 12 prospective cohort studies from Europe and the United States (the HIV-CAUSAL Collaboration) that includes 62 760 HIV-infected, therapy-naive individuals followed for an average of 3.3 years. Inverse probability weighting of marginal structural models was used to adjust for measured confounding by indication.

RESULTS

Two thousand and thirty-nine individuals died during the follow-up. The mortality hazard ratio was 0.48 (95% confidence interval 0.41-0.57) for cART initiation versus no initiation. In analyses stratified by CD4 cell count at baseline, the corresponding hazard ratios were 0.29 (0.22-0.37) for less than 100 cells/microl, 0.33 (0.25-0.44) for 100 to less than 200 cells/microl, 0.38 (0.28-0.52) for 200 to less than 350 cells/microl, 0.55 (0.41-0.74) for 350 to less than 500 cells/microl, and 0.77 (0.58-1.01) for 500 cells/microl or more. The estimated hazard ratio varied with years since initiation of cART from 0.57 (0.49-0.67) for less than 1 year since initiation to 0.21 (0.14-0.31) for 5 years or more (P value for trend <0.001).

CONCLUSION

We estimated that cART halved the average mortality rate in HIV-infected individuals. The mortality reduction was greater in those with worse prognosis at the start of follow-up.

Interleukin-2 therapy in patients with HIV infection

BACKGROUND

Used in combination with antiretroviral therapy, subcutaneous recombinant interleukin-2 raises CD4+ cell counts more than does antiretroviral therapy alone. The clinical implication of these increases is not known.

METHODS

We conducted two trials: the Subcutaneous Recombinant, Human Interleukin-2 in HIV-Infected Patients with Low CD4+ Counts under Active Antiretroviral Therapy (SILCAAT) study and the Evaluation of Subcutaneous Proleukin in a Randomized International Trial (ESPRIT). In each, patients infected with the human immunodeficiency virus (HIV) who had CD4+ cell counts of either 50 to 299 per cubic millimeter (SILCAAT) or 300 or more per cubic millimeter (ESPRIT) were randomly assigned to receive interleukin-2 plus antiretroviral therapy or antiretroviral therapy alone. The interleukin-2 regimen consisted of cycles of 5 consecutive days each, administered at 8-week intervals. The SILCAAT study involved six cycles and a dose of 4.5 million IU of interleukin-2 twice daily; ESPRIT involved three cycles and a dose of 7.5 million IU twice daily. Additional cycles were recommended to maintain the CD4+ cell count above predefined target levels. The primary end point of both studies was opportunistic disease or death from any cause.

RESULTS

In the SILCAAT study, 1695 patients (849 receiving interleukin-2 plus antiretroviral therapy and 846 receiving antiretroviral therapy alone) who had a median CD4+ cell count of 202 cells per cubic millimeter were enrolled; in ESPRIT, 4111 patients (2071 receiving interleukin-2 plus antiretroviral therapy and 2040 receiving antiretroviral therapy alone) who had a median CD4+ cell count of 457 cells per cubic millimeter were enrolled. Over a median follow-up period of 7 to 8 years, the CD4+ cell count was higher in the interleukin-2 group than in the group receiving antiretroviral therapy alone--by 53 and 159 cells per cubic millimeter, on average, in the SILCAAT study and ESPRIT, respectively. Hazard ratios for opportunistic disease or death from any cause with interleukin-2 plus antiretroviral therapy (vs. antiretroviral therapy alone) were 0.91 (95% confidence interval [CI], 0.70 to 1.18; P=0.47) in the SILCAAT study and 0.94 (95% CI, 0.75 to 1.16; P=0.55) in ESPRIT. The hazard ratios for death from any cause and for grade 4 clinical events were 1.06 (P=0.73) and 1.10 (P=0.35), respectively, in the SILCAAT study and 0.90 (P=0.42) and 1.23 (P=0.003), respectively, in ESPRIT.

CONCLUSIONS

Despite a substantial and sustained increase in the CD4+ cell count, as compared with antiretroviral therapy alone, interleukin-2 plus antiretroviral therapy yielded no clinical benefit in either study. (ClinicalTrials.gov numbers, NCT00004978 [ESPRIT] and NCT00013611 [SILCAAT study].)

CCL3L1-CCR5 genotype improves the assessment of AIDS Risk in HIV-1-infected individuals

BACKGROUND

Whether vexing clinical decision-making dilemmas can be partly addressed by recent advances in genomics is unclear. For example, when to initiate highly active antiretroviral therapy (HAART) during HIV-1 infection remains a clinical dilemma. This decision relies heavily on assessing AIDS risk based on the CD4+ T cell count and plasma viral load. However, the trajectories of these two laboratory markers are influenced, in part, by polymorphisms in CCR5, the major HIV coreceptor, and the gene copy number of CCL3L1, a potent CCR5 ligand and HIV-suppressive chemokine. Therefore, we determined whether accounting for both genetic and laboratory markers provided an improved means of assessing AIDS risk.

METHODS AND FINDINGS

In a prospective, single-site, ethnically-mixed cohort of 1,132 HIV-positive subjects, we determined the AIDS risk conveyed by the laboratory and genetic markers separately and in combination. Subjects were assigned to a low, moderate or high genetic risk group (GRG) based on variations in CCL3L1 and CCR5. The predictive value of the CCL3L1-CCR5 GRGs, as estimated by likelihood ratios, was equivalent to that of the laboratory markers. GRG status also predicted AIDS development when the laboratory markers conveyed a contrary risk. Additionally, in two separate and large groups of HIV+ subjects from a natural history cohort, the results from additive risk-scoring systems and classification and regression tree (CART) analysis revealed that the laboratory and CCL3L1-CCR5 genetic markers together provided more prognostic information than either marker alone. Furthermore, GRGs independently predicted the time interval from seroconversion to CD4+ cell count thresholds used to guide HAART initiation.

CONCLUSIONS

The combination of the laboratory and genetic markers captures a broader spectrum of AIDS risk than either marker alone. By tracking a unique aspect of AIDS risk distinct from that captured by the laboratory parameters, CCL3L1-CCR5 genotypes may have utility in HIV clinical management. These findings illustrate how genomic information might be applied to achieve practical benefits of personalized medicine.

Clinical outcome of HIV-infected antiretroviral-naive patients with discordant immunologic and virologic responses to highly active antiretroviral therapy

BACKGROUND

The prognostic significance of a response to highly active antiretroviral therapy (HAART) that is immunologically and virologically discordant is not well understood.

METHODS

Four hundred four antiretroviral-naive patients initiating HAART at an urban HIV outpatient clinic in 1995 to 2004 were analyzed. The association of treatment responses at 3 to 9 months after HAART initiation with time to development of an opportunistic infection (OI) or death was determined using Cox proportional hazards modeling. Logistic regression modeling was used to examine the association between discordant responses and patient characteristics.

RESULTS

Of 404 patients, 70.5% experienced favorable concordant responses (CD4 cell count [CD4]+/viral load [VL]+: increase in CD4 count of >or=50 cells/microL and achievement of undetectable plasma HIV RNA level), 15.8% an immunologic response only (CD4+/VL(-)), 8.7% a virologic response only (CD4(-)/VL+), and 5.0% a concordant unfavorable response (CD4(-)/VL(-)). Both types of discordant responses (CD4+/VL(-) and CD4(-)/VL+), nonresponse (CD4(-)/VL(-)), and baseline CD4 cell count were significantly associated with earlier development of an OI or death (relative hazard [RH] = 2.81, 95% confidence interval [CI]: 1.31 to 3.97; RH = 4.83, 95% CI: 2.10 to 11.12; and RH = 0.93, 95% CI: 0.88 to 0.99, respectively). CD4+/VL(-) and CD4(-)/VL(-) were associated with nonwhite race in multivariate logistic regression models (adjusted OR = 2.83, 95% CI: 1.46 to 5.47 and adjusted OR = 6.50, 95% CI: 1.65 to 25.69, respectively).

CONCLUSION

Discordant immunologic and virologic responses at 3 to 9 months after HAART initiation play important roles in predicting long-term clinical outcomes in treatment-naive patients.

Drug development and the FDA's Critical Path Initiative

Advances in biomedical research over recent decades have substantially raised expectations that the pharmaceutical industry will generate increasing numbers of safe and effective therapies. However, there are warning signs of serious limitations in the industry's ability to effectively translate biomedical research into marketed new therapies. Clinical pharmacologists should be aware of these signals and their potential impact. Here, we discuss a strategy, where clinical pharmacology can play an important role to improve the process of drug development.

Prevalence of HIV status and CD4 counts in a surgical cohort: their relationship to clinical outcome

INTRODUCTION

HIV positivity alone as a predictor of surgical outcome has not been extensively studied in regions of high prevalence. The aim was to determine the prevalence of HIV infection in surgical patients, and compare differences in their clinical course based on their serological status and CD4 counts.

PATIENTS AND METHODS

A prospective cohort of 350 patients, enrolled over 6 weeks, were studied. HIV status was determined in all patients. HIV-positive patients had CD4 counts. Clinical details were collated with HIV data after completion of enrollment.

RESULTS

Of the 350 patients, all but 6 were black South Africans. The median age was 31 years (range, 18-82 years). There were 143 trauma and 207 non-trauma patients. The male:female ratio was 1.4:1. The overall HIV seropositivity rate was 39% (females, 46%; males, 36%). Overall, 228 patients had surgical intervention and 96 patients had drainage of sepsis. The hospital stay (HIV negative, 11.9 +/- 15.9 days; HIV positive, 11.0 +/- 15 days) and mortality (HIV positive, 3.6%; HIV negative, 3.7%) did not differ by major diagnostic category. For HIV-positive patients, the male:female ratio was 1.2:1. There were 54 trauma and 83 non-trauma patients. An operation for the drainage of a septic focus was commoner in the HIV-positive admissions. Thirty-two (24%) patients had CD4 counts less than 200 cells/mm3, (i.e. AIDS). The hospital mortality, hospital stay and severity of sepsis were not related to CD4 counts.

CONCLUSIONS

HIV status does not influence the outcome of general surgical admissions and should not influence surgical management decisions. In HIV-positive surgical patients, CD4 counts have no relation to in-hospital outcome in a heterogeneous group of surgical patients.

Prolonged survival of end-stage AIDS patients immunized with therapeutic HIV vaccine V-1 Immunitor

Death, rather than surrogate markers, is a single and most straightforward clinical endpoint, defining unequivocally the merit of a therapeutic intervention. As there is still neither a cure for AIDS nor a vaccine to prevent HIV infection, an AIDS diagnosis remains associated with a death sentence. V-1 Immunitor (V1) is an experimental, oral, therapeutic AIDS vaccine licensed as a dietary supplement. As part of a charity program V1 has been offered at Wat Phra Baht Nam Phu--a Buddhist hospice for end-stage AIDS patients. Out of 117 approached individuals, 53 decided to take V1 and 64 declined the treatment. Patients in both groups did not differ in age, gender, or severity of disease. All patients were in WHO terminal stage 4 at study entry and had received similar palliative care. None of the patients had received conventional antiviral drugs. At 9 weeks the last two patients in the non-V1 group died. In contrast, 56.6% (30/53) in the V1 group remained alive. Kaplan-Meier survival analysis showed that median short-term survival time for non-treated and treated patients was 4 and 10 weeks, respectively. The difference was statistically significant by Wilcoxon signed rank test (P=0.000089). Patients who remained alive were followed until the last patient died at 142 weeks. Based on the main outcome, i.e. time to death, patients on V1 had a 15.8 times longer life expectancy than the control group (P<0.000001). Observed results are encouraging and V1 needs to be tested in controlled clinical trials as a life-saving immunotherapy.

Long-term effectiveness of potent antiretroviral therapy in preventing AIDS and death: a prospective cohort study

BACKGROUND

Evidence on the effectiveness of highly active antiretroviral therapy (HAART) for HIV-infected individuals is limited. Most clinical trials examined surrogate endpoints over short periods of follow-up and there has been no placebo-controlled randomised trial of HAART. Estimation of treatment effects in observational studies is problematic, because of confounding by indication. We aimed to use novel methodology to overcome this problem in the Swiss HIV Cohort Study.

METHODS

Patients were included if they had been examined after January 1996, when HAART became available in Switzerland, were not on HAART, and were free of AIDS at baseline. Cox regression models were weighted to create a statistical population in which the probability of being treated at each time point was unrelated to prognostic factors.

RESULTS

Low CD4 counts and increasing HIV-1 viral load were associated with increased probability of starting HAART. Overall hazard ratios were 0.14 (95% CI 0.07-0.29) for HAART compared with no treatment, and 0.49 (0.31-0.79) compared with dual therapy. Compared with no treatment, HAART became more beneficial with increasing time since initiation but was less beneficial for patients whose presumed mode of transmission was via intravenous drug use (hazard ratio 0.27, 0.12-0.61) than for other patients (0.08, 0.03-0.19).

INTERPRETATION

Our results, which are appropriately controlled for confounding by indication, are consistent with reported declines in rates of AIDS and death in developed countries, and provide a context in which to consider adverse effects of HAART.

Phase II placebo-controlled study of V-1 Immunitor as a therapeutic modality for treatment of HIV

BACKGROUND

V-1 Immunitor (V1) is an oral AIDS vaccine containing heat- and chemically-inactivated viral antigens derived from pooled blood of HIV-positive donors. V1 has a pending status as an investigational drug but is currently marketed as a dietary supplement. Earlier published, uncontrolled studies of V1 demonstrated body weight gain, increase in T-lymphocyte numbers, decrease in viral load, and improved survival of end-stage AIDS patients.

OBJECTIVES AND STUDY DESIGN

In order to substantiate prior observations we have undertaken a placebo-controlled phase II clinical trial involving 47 antiviral therapy naive, asymptomatic individuals who had over 350 mm(3) CD4 T-cells (mean/median 538/480) at study entry. Both placebo and treatment arms were identical demographically and by every clinical parameter measured at baseline.

RESULTS AND CONCLUSIONS

At the end of 6-month follow-up 29 volunteers who received V1 b.i.d. had gained on average 43 CD4 T-cells (540 versus 583). This gain was statistically significant (p=0.01) while changes in T-cell numbers in placebo group failed to reach the significance threshold (p=0.33). The clinical potential of V1 is further supported by an elevation in CD4/CD8 ratio among V1 recipients and decline in CD4/CD8 ratio in patients on placebo (0.575 versus 0.524; p=0.02). The average weight gain among patients on V1 was 1.8 kg while placebo group lost 0.5 kg. These results suggest that V1 may delay or reverse the disease progression without any concurrent toxicity and support our prior open-label studies indicating that V1 confers clinical benefit. A phase III clinical study is required to confirm these findings and to allow us to seek license for V1 as a therapeutic AIDS vaccine.

Publications in Anesthesia Journals: Quality and Clinical Relevance

Clinicians performing evidence-based anesthesia rely on anesthesia journals for clinically relevant information. The objective of this study was to analyze the proportion of clinically relevant articles in five high impact anesthesia journals. We evaluated all articles published in Anesthesiology, Anesthesia & Analgesia, British Journal of Anesthesia, Anesthesia, and Acta Anaesthesiologica Scandinavica from January to June, 2000. Articles were assessed and classified according to type, outcome, and design; 1379 articles consisting of 5468 pages were evaluated and categorized. The most common types of article were animal and laboratory research (31.2%) and randomized clinical trial (20.4%). A clinically relevant article was defined as an article that used a statistically valid method and had a clinically relevant end-point. Altogether 18.6% of the pages had as their subject matter clinically relevant trials. We compared the Journal Impact Factor (a measure of the number of citations per article in a journal) and the proportion of clinically relevant pages and found that they were inversely proportional to each other.

Prognosis of HIV-1-infected patients starting highly active antiretroviral therapy: a collaborative analysis of prospective studies

BACKGROUND

Insufficient data are available from single cohort studies to allow estimation of the prognosis of HIV-1 infected, treatment-naive patients who start highly active antiretroviral therapy (HAART). The ART Cohort Collaboration, which includes 13 cohort studies from Europe and North America, was established to fill this knowledge gap.

METHODS

We analysed data on 12,574 adult patients starting HAART with a combination of at least three drugs. Data were analysed by intention-to-continue-treatment, ignoring treatment changes and interruptions. We considered progression to a combined endpoint of a new AIDS-defining disease or death, and to death alone. The prognostic model that generalised best was a Weibull model, stratified by baseline CD4 cell count and transmission group. FINDINGS During 24,310 person-years of follow up, 1094 patients developed AIDS or died and 344 patients died. Baseline CD4 cell count was strongly associated with the probability of progression to AIDS or death: compared with patients starting HAART with less than 50 CD4 cells/microL, adjusted hazard ratios were 0.74 (95% CI 0.62-0.89) for 50-99 cells/microL, 0.52 (0.44-0.63) for 100-199 cells/microL, 0.24 (0.20-0.30) for 200-349 cells/microL, and 0.18 (0.14-0.22) for 350 or more CD4 cells/microL. Baseline HIV-1 viral load was associated with a higher probability of progression only if 100,000 copies/microL or above. Other independent predictors of poorer outcome were advanced age, infection through injection-drug use, and a previous diagnosis of AIDS. The probability of progression to AIDS or death at 3 years ranged from 3.4% (2.8-4.1) in patients in the lowest-risk stratum for each prognostic variable, to 50% (43-58) in patients in the highest-risk strata.

INTERPRETATION

The CD4 cell count at initiation was the dominant prognostic factor in patients starting HAART. Our findings have important implications for clinical management and should be taken into account in future treatment guidelines.

Durable HIV-1 Suppression with Indinavir after Failing Lamivudine-Containing Double Nucleoside Therapy: A Randomized Controlled Trial

Objective

To assess the durability of the antiretroviral effect in plasma and cerebrospinal fluid (CSF) of antiviral therapy intensification, produced by the addition of indinavir from week 12 onwards to the original regimen of zidovudine/lamivudine or stavudine/lamivudine, after 72 weeks of follow-up using an ultrasensitive HIV-1 RNA assay. To assess CSF concentrations of indinavir at week 48.

Design

In a prospectively, randomized, open, single-centre study, antiretroviral-naive patients (CD4 cell count ≥200 cells/μl and a plasma HIV-1 RNA level ≥10000 copies/ml) were assigned to a combination of zidovudine/lamivudine or stavudine/lamivudine. Indinavir could be added to the double nucleoside analogue regimen from week 12 or thereafter in case the plasma HIV RNA level was insufficiently suppressed (>500 copies/ml).

Results

Forty-seven patients were enrolled (23 stavudine/lamivudine and 24 zidovudine/lamivudine), of whom 33 completed a follow-up of 72 weeks. Indinavir was added in 89% (42/47) of the patients. Only one discontinuation occurred due to virological failure. At week 72, the median plasma HIV-1 RNA levels in the zidovudine/lamivudine group had decreased from 4.80 log10 copies/ml to <500 copies/ml in 100% of patients and <50 copies/ml in 86.6% of the patients. In the stavudine/lamivudine group the plasma HIV-1 RNA decreased from 4.98 log10 copies/ml at baseline to <500 copies/ml in 100% of patients and <50 copies/ml in 66.7% of the patients. On an intent-to-treat basis these figures were 54.2 and 52.2% for zidovudine/lamivudine and stavudine/lamivudine, respectively, for the 50 copies/ml assay. The median CD4 cell count increased from 315 cells/μl, with 150 cells/μl in the zidovudine/lamivudine arm, and from 290 cells/μl, with 310 cells/μl in the stavudine/lamivudine arm ( P=0.0001). However, the percentage of CD4 cells did not differ in each group. In the zidovudine/lamivudine group 9/10 and 5/5, and in the stavudine/lamivudine group 11/11 and 6/6 had a CSF HIV-1 RNA level <50 copies/ml at week 12 and 48, respectively. The CSF indinavir concentration ranged from 50 to 170 ng/ml.

Conclusion

The long-term HIV-1 suppression observed in this study is remarkable, as adding a single antiretroviral agent to a failing regimen goes against current notions of adequate therapy.

Predictors of operative outcome in patients with human immunodeficiency virus infection and acquired immunodeficiency syndrome

BACKGROUND

Plasma viral load has recently been associated with clinical outcome in patients with human immunodeficiency virus (HIV) infection and acquired immunodeficiency syndrome (AIDS). We hypothetized that, in addition to CD4 lymphocytes, plasma HIV-1 RNA counts are predictive of postoperative outcome.

METHODS

HIV-infected and AIDS patients admitted to a major teaching hospital requiring invasive or surgical procedures were retrospectively analyzed for postoperative outcome. Preoperative and postoperative immune cell counts including plasma HIV-1 RNA counts were recorded. Chi-square analysis, Fisher's exact test, and multivariate regression were performed with statistical significance P </=0.05.

RESULTS

Fifty-five consecutive patients between 14 and 62 years of age were admitted in a 1-year period and underwent 64 diagnostic and therapeutic procedures. Fourteen (22%) postoperative infections and 18 (28%) complications other than infection, with an overall mortality of 11%, were documented. Total preoperative white blood cell count ([WBC] P <0.01), preoperative percent lymphocyte count (P <0.01), absolute postoperative CD4 lymphocyte count (P <0.01), and postoperative plasma viral load (P <0.0001) are associated with mortality. Multivariate regression indicated that postoperative percent CD4 lymphocyte count is an independent predictor of both postoperative infection and other complications (P <0.05, R = 0.848, power = 0.9911), while the decrement in percent CD4 lymphocyte count is an independent predictor of postoperative complications other than infection (P <0.05, R = 0.596, power = 0.7838).

CONCLUSIONS

In accordance with the medical literature for clinical outcome in HIV-infected and AIDS patients, both immune cell counts and HIV-1 RNA counts were found to associate with postoperative mortality. However, the postoperative and decrement in percent CD4 lymphocyte proved to be the independent predictors of postoperative complications.

Human immunodeficiency virus type 1 RNA level and CD4 count as prognostic markers and surrogate end points: a meta-analysis. HIV Surrogate Marker Collaborative Group

OBJECTIVE

To evaluate treatment-mediated changes in HIV-1 RNA and CD4 count as prognostic markers and surrogate end points for disease progression (AIDS/death).

METHODS

Data from 13,045 subjects in all 16 randomized trials comparing nucleoside analogue reverse transcriptase inhibitors and having HIV-1 RNA measurements at 24 weeks were obtained. A total of 3146 subjects had HIV-1 RNA and CD4 count determinations at 24 weeks after starting treatment.

RESULTS

At Week 24, the percentage of subjects experiencing an HIV-1 RNA decrease of >1 log10 copies/ml or a CD4 count increase of >33% was similar (22% vs. 25%). Changes in both markers at Week 24 were significant independent predictors of AIDS/death: across trials, the average reduction in hazard was 51% per 1 log10 HIV-1 RNA copies/ml decrease (95% confidence interval: 41%, 59%) and 20% per 33% CD4 count increase (17%, 24%). In univariate analyses, the hazard ratio for AIDS/death in randomized treatment comparisons was significantly associated with differences between treatments in mean area under the curve of HIV-1 RNA changes to Weeks 8 and 24 (AUCMB) and mean CD4 change at Week 24, but, in multivariate analysis, only mean CD4 change was significant.

CONCLUSIONS

Change in HIV-1 RNA, particularly using AUCMB, and in CD4 count should be measured to aid patient management and evaluation of treatment activity in clinical trials. However, short-term changes in these markers are imperfect as surrogate end points for long-term clinical outcome because two randomized treatment comparisons may show similar differences between treatments in marker changes but not similar differences in progression to AIDS/death.

Some statistical issues in the design of HIV-1 vaccine and treatment trials

This article summarizes material on statistical issues in the design of HIV-1 preventive vaccine trials and antiretroviral HIV-1 treatment trials that was presented at the first school on Modern Statistical Methods in Medical Research, held at the International Centre for Theoretical Physics in Trieste, in September 1999. Design issues for the two trial types are discussed separately and are compared, which highlights the relative complexity of vaccine trials. Vaccine trial designs for assessing various vaccine effects are considered, including classical double-blind individual-randomized designs for evaluating biological vaccine effects on susceptibility to infection, and augmented partners, cluster-randomized, and infant designs for evaluating biological vaccine effects on infectiousness as well as on susceptibility. Within these designs, covered topics include surrogate endpoints for measuring vaccine effects on secondary transmission and on HIV-1 disease progression, and exploratory and confirmatory methods for assessing host immune and viral genotypic or phenotypic correlates of vaccine protection against infection or disease. For antiretroviral trials, covered topics include endpoint selection and structured designs such as fractional factorial and Latin square designs for rapidly screening combination drug regimens and for identifying patterns of HIV-1 genomic evolution that predict loss of drug efficacy.