Staging system for clinical AIDS patients. Royal Free/Chelsea and Westminster Hospitals Collaborative Group

Comparative Analysis of Tat-Dependent and Tat-Deficient Natural Lentiviruses

The emergence of human immunodeficiency virus (HIV) causing acquired immunodeficiency syndrome (AIDS) in infected humans has resulted in a global pandemic that has killed millions. HIV-1 and HIV-2 belong to the lentivirus genus of the Retroviridae family. This genus also includes viruses that infect other vertebrate animals, among them caprine arthritis-encephalitis virus (CAEV) and Maedi-Visna virus (MVV), the prototypes of a heterogeneous group of viruses known as small ruminant lentiviruses (SRLVs), affecting both goat and sheep worldwide. Despite their long host-SRLV natural history, SRLVs were never found to be responsible for immunodeficiency in contrast to primate lentiviruses. SRLVs only replicate productively in monocytes/macrophages in infected animals but not in CD4+ T cells. The focus of this review is to examine and compare the biological and pathological properties of SRLVs as prototypic Tat-independent lentiviruses with HIV-1 as prototypic Tat-dependent lentiviruses. Results from this analysis will help to improve the understanding of why and how these two prototypic lentiviruses evolved in opposite directions in term of virulence and pathogenicity. Results may also help develop new strategies based on the attenuation of SRLVs to control the highly pathogenic HIV-1 in humans.

Predictive accuracy of the Veterans Aging Cohort Study index for mortality with HIV infection: a North American cross cohort analysis

BACKGROUND

By supplementing an index composed of HIV biomarkers and age (restricted index) with measures of organ injury, the Veterans Aging Cohort Study (VACS) index more completely reflects risk of mortality. We compare the accuracy of the VACS and restricted indices (1) among subjects outside the Veterans Affairs Healthcare System, (2) more than 1-5 years of prior exposure to antiretroviral therapy (ART), and (3) within important patient subgroups.

METHODS

We used data from 13 cohorts in the North American AIDS Cohort Collaboration (n = 10, 835) limiting analyses to HIV-infected subjects with at least 12 months exposure to ART. Variables included demographic, laboratory (CD4 count, HIV-1 RNA, hemoglobin, platelets, aspartate and alanine transaminase, creatinine, and hepatitis C status), and survival. We used C-statistics and net reclassification improvement (NRI) to test discrimination varying prior ART exposure from 1 to 5 years. We then combined Veterans Affairs Healthcare System (n = 5066) and North American AIDS Cohort Collaboration data, fit a parametric survival model, and compared predicted to observed mortality by cohort, gender, age, race, and HIV-1 RNA level.

RESULTS

Mean follow-up was 3.3 years (655 deaths). Compared with the restricted index, the VACS index showed greater discrimination (C-statistics: 0.77 vs. 0.74; NRI: 12%; P < 0.0001). NRI was highest among those with HIV-1 RNA <500 copies per milliliter (25%) and age ≥50 years (20%). Predictions were similar to observed mortality among all subgroups.

CONCLUSIONS

VACS index scores discriminate risk and translate into accurate mortality estimates over 1-5 years of exposure to ART and for diverse patient subgroups from North American.

Towards a combined prognostic index for survival in HIV infection: the role of 'non-HIV' biomarkers

BACKGROUND

As those with HIV infection live longer, 'non-AIDS' condition associated with immunodeficiency and chronic inflammation are more common. We ask whether 'non-HIV' biomarkers improve differentiation of mortality risk among individuals initiating combination antiretroviral therapy (cART).

METHODS

Using Poisson models, we analysed data from the Veterans Aging Cohort Study (VACS) on HIV-infected veterans initiating cART between 1 January 1997 and 1 August 2002. Measurements included: HIV biomarkers (CD4 cell count, HIV RNA and AIDS-defining conditions); 'non-HIV' biomarkers (haemoglobin, transaminases, platelets, creatinine, and hepatitis B and C serology); substance abuse or dependence (alcohol or drug); and age. Outcome was all cause mortality. We tested the discrimination (C statistics) of each biomarker group alone and in combination in development and validation data sets, over a range of survival intervals, and adjusting for missing data.

RESULTS

Of veterans initiating cART, 9784 (72%) had complete data. Of these, 2566 died. Subjects were middle-aged (median age 45 years), mainly male (98%) and predominantly black (51%). HIV and 'non-HIV' markers were associated with each other (P < 0.0001) and discriminated mortality (C statistics 0.68-0.73); when combined, discrimination improved (P < 0.0001). Discrimination for the VACS Index was greater for shorter survival intervals [30-day C statistic 0.86, 95% confidence interval (CI) 0.80-0.91], but good for intervals of up to 8 years (C statistic 0.73, 95% CI 0.72-0.74). Results were robust to adjustment for missing data.

CONCLUSIONS

When added to HIV biomarkers, 'non-HIV' biomarkers improve differentiation of mortality. When evaluated over similar intervals, the VACS Index discriminates as well as other established indices. After further validation, the VACS Index may provide a useful, integrated risk assessment for management and research.

Prognostic Significance of Immune Subset Measurement in Individuals With AIDS-Associated Kaposi's Sarcoma

Purpose

A prognostic index for AIDS-associated Kaposi's sarcoma (KS) diagnosed in the era of highly active antiretroviral therapy (HAART) was based on routine clinical and laboratory characteristics. Because immune subset measurement is often performed in HIV-positive individuals, we examined whether these were predictive of mortality independently of the prognostic index, or could predict time to progression of KS.

Patients and Methods

We performed univariate and multivariate Cox regression analyses on a data set of 326 individuals with AIDS-associated KS to identify immune subset covariates predictive of overall survival and time to progression. Adaptive (CD8 T cell and CD19 B cell) and innate (CD16/56 natural-killer cell) immune parameters were studied by flow cytometry.

Results

In univariate analyses, all three immune subsets had significant effects on overall survival (P < .025). In multivariate analyses including the prognostic index, only CD8 counts remained significant (P = .026), although its effect on the overall prognostic index is small. An increase of 100 cells/mm3 in the CD8 count confers a 5% improvement in overall survival. Individuals with a higher CD8 count did not have an increased time to progression. Patients who were already on HAART at the time of KS diagnosis did not have a shorter time to progression than those who were antiretroviral naïve at KS diagnosis.

Conclusion

The CD8 count appears to provide independent prognostic information in individuals with AIDS-associated KS. Measurement of the CD8 count is clinically useful in patients with KS.

Predictors of death within six months in patients with advanced AIDS

OBJECTIVES

This study sought to identify potential predictive variables of death within 6 months in patients with advanced AIDS.

METHODS

Investigators enrolled a consecutive series of patients with advanced AIDS admitted to a skilled nursing facility in New York City over a 1-year period. Demographic, clinical, laboratory, and outcome data were abstracted from medical records using a standardized data collection instrument.

RESULTS

Of the 152 patients enrolled during the study period, 61 patients (40%) died within 6 months from date of admission. Serum albumin, percent deviation from ideal body weight, and number of comorbidities at the time of admission proved to be the best combination of predictors of death within 6 months.

SIGNIFICANCE OF RESULTS

The decrease in AIDS mortality over the past decade, along with an increase in prevalence due to longer survival, has been attributed primarily to the successful use of highly active antiretroviral therapy (HAART). HAART regimens, however, can also produce both short-term adverse effects and long-term complications. The prognostic model developed by this study may be useful in guiding treatment decisions in patients with advanced AIDS for whom a more palliative care plan may be sought.

Effect of tuberculosis preventive therapy on HIV disease progression and survival in HIV-infected adults

PURPOSE

To determine whether tuberculosis (TB) preventive therapies alter the rate of disease progression to AIDS or death and to identify significant prognostic factors for HIV disease progression to AIDS.

METHOD

In a randomized placebo-controlled trial in Kampala, Uganda, 2,736 purified protein derivative (PPD)-positive and anergic HIV-infected adults were randomly assigned to four and two regimens, respectively. PPD-positive patients were treated with isoniazid (INH) for 6 months (6H; n = 536), INH plus rifampicin for 3 months (3HR; n = 556), INH plus rifampicin plus pyrazinamide for 3 months (3HRZ; n = 462), or placebo for 6 months (n = 464). Anergic participants were treated with 6H (n = 395) or placebo (n = 323).

RESULTS

During follow-up, 404 cases progressed to AIDS and 577 deaths occurred. The cumulative incidence of the AIDS progression was greater in the anergic cohort compared to the PPD-positive cohort (p < .0001). Among PPD-positive patients, the relative risk of the AIDS progression with INH alone was 0.95 (95% CI 0.68-1.32); with 3HR it was 0.83 (95% CI 0.59-1.17); and with 3HRZ it was 0.76 (95% CI 0.52-1.08), controlling for significant baseline predictors. Among anergic patients, the relative risk of the AIDS progression was 0.81 (95% CI 0.56-1.15). Survival was greater in the PPD-positive cohort compared to the anergic cohort (p = .0001).

CONCLUSION

The number of signs or symptoms at baseline and anergic status are associated with increasing morbidity and mortality. Even though the tuberculosis preventive therapies were effective in reducing the incidence of TB for HIV-infected adults, their benefit of delaying HIV disease progression to AIDS was not observed.

Grey nails predict low CD4 cell count among untreated patients with HIV infection in Malawi

BACKGROUND

Alternative criteria for initiating antiretroviral therapy to CD4 testing or clinical illness are needed in Malawi.

METHOD

We tested if grey nails could be used to identify patients with a CD4 cell count less than 200 cells/microl who had not yet presented with AIDS-defining illnesses.

RESULTS

Using a set of 242 photographs we showed good inter-observer agreement for grey nails (kappa = 0.66; P < 0.0001) and the positive predictive value of grey nails for a CD4 cell count of less than 200 cells/microl was 81% (chi < 0.0001).

CONCLUSIONS

Grey nails have been associated with HIV infection and we have shown significant correlation of this sign with a low CD4 cell count. For clinicians working in sub-Saharan Africa without access to CD4 cell count testing, grey or DB nails represent an additional staging sign to help identify a sub-group of patients likely to benefit from ART.

Validity and reliability of the Italian translation of the MOS-HIV health survey in persons with AIDS

OBJECTIVES

To evaluate the validity and reliability of the Italian version of the 35-item Medical Outcome Study HIV Health Survey (MOS-HIV) when applied to persons with AIDS.

METHODS

The study population consisted of 185 adults with AIDS residing in Rome and participating in a randomised controlled trial on home-care. Diagnosis was made between 1 October 1994 and 1 April 1996, and enrollment took place within 2 months of diagnosis. The MOS-HIV, which measures 10 dimensions of health-related quality of life (QoL), was administered at baseline and every 3 months thereafter during the 1-year follow-up. Tests of convergent and concurrent construct validity were conducted for all scales.

RESULTS

Of the 185 trial participants, 146 responded to the questionnaire; 82 responded at least twice (including baseline collection) during follow-up. For the role functioning, general health, and vitality scales, the distribution of scale scores was concentrated at the lower half of the range. Internal consistency reliability was adequate (>0.80) for all scales. Baseline scores tended to increase with decreasing AIDS severity and with increasing age. There were improvements over time in the role functioning, vitality, and health distress scales.

CONCLUSIONS

The MOS-HIV had good reliability among persons with AIDS. There was a moderate floor effect for some of the subscales. Tests of convergent and construct validity were generally confirmed. Additional studies are needed to evaluate the responsiveness to changes over time.

External validity of predictive models: a comparison of logistic regression, classification trees, and neural networks

BACKGROUND AND OBJECTIVE

The utility of predictive models depends on their external validity, that is, their ability to maintain accuracy when applied to patients and settings different from those on which the models were developed. We report a simulation study that compared the external validity of standard logistic regression (LR1), logistic regression with piecewise-linear and quadratic terms (LR2), classification trees, and neural networks (NNETs).

METHODS

We developed predictive models on data simulated from a specified population and on data from perturbed forms of the population not representative of the original distribution. All models were tested on new data generated from the population.

RESULTS

The performance of LR2 was superior to that of the other model types when the models were developed on data sampled from the population (mean receiver operating characteristic [ROC] areas 0.769, 0.741, 0.724, and 0.682, for LR2, LR1, NNETs, and trees, respectively) and when they were developed on nonrepresentative data (mean ROC areas 0.734, 0.713, 0.703, and 0.667). However, when the models developed using nonrepresentative data were compared with models developed from data sampled from the population, LR2 had the greatest loss in performance.

CONCLUSION

Our results highlight the necessity of external validation to test the transportability of predictive models.

Impact of tuberculosis on HIV disease progression in persons with well-documented time of HIV seroconversion

Tuberculosis (TB) enhances HIV replication in vitro, but its impact on HIV progression at the population level is not established. Studies from industrialized and nonindustrialized countries show contradictory results as to whether TB accelerates HIV progression, although no studies have been conducted in persons with well-documented seroconversion times. Data from HIV seroconverters from 19 cohorts were analyzed to examine the effect of TB on HIV progression comparing persons with TB and persons without TB infected by HIV for the same length of time. TB and other AIDS-defining conditions (ADCs) were fitted as time-dependent covariates, adjusting for age, sex, transmission category, calendar year at risk, and cohort, using Cox proportional hazards models and allowing for late entry. Of 4398 seroconverters, 1294 (29%) developed AIDS. TB accounted for 72 (5.6%) of initial ADCs and for 105 (5.7%) of all ADCs. Survival from HIV seroconversion shows that compared with AIDS-free subjects, the risk of death associated with TB as an initial ADC (hazard ratio [HR] = 23.23, 95% CI: 14.60-36.96) does not differ from that associated with Kaposi sarcoma (HR = 23.47, 95% CI: 16.66-33.05) or esophageal candidiasis (OC)/Pneumocystis carinii pneumonia (PCP) (HR = 30.97, 95% CI: 24.38-39.34) but is lower than that for opportunistic infections other than TB, OC/PCP (HR = 46.83, 95% CI: 37.86-47.94) and high-grade non-Hodgkin lymphomas/invasive cervical carcinoma (HR = 92.71, 95% CI: 60.83-141.3). The lowest risk of death was seen, as expected, in AIDS-free subjects. HIV progression is not inherently faster in subjects who develop TB compared with other individuals with AIDS who have been infected by HIV for the same length of time in countries where TB treatment is widely available.

Difference in the incidence of Clostridium difficile among patients infected with human immunodeficiency virus admitted to a public hospital and a private hospital

OBJECTIVE

To compare the occurrence of Clostridium difficile among inpatients infected with human immunodeficiency virus (HIV) in two different hospitals.

DESIGN

Prospective, observational study.

SETTING

Specialized HIV inpatient units.

PATIENTS

HIV-infected inpatients at Cook County Hospital (CCH) and Rush Presbyterian St. Luke's Medical Center (RPSLMC).

INTERVENTIONS

A clinical and epidemiologic assessment of patient risk factors for C. difficile was performed. C. difficile isolates found on stool, rectal, and environmental cultures were typed by pulsed-field gel electrophoresis.

RESULTS

Twenty-seven percent of patients admitted to CCH versus 4% of patients admitted to RPSLMC had positive cultures for C. difficile (P = .001). At CCH, 14.7% of environmental cultures were positive versus 2.9% at RPSLMC (P = .002). Risk factors for C. difficile acquisition included hospitalization at CCH, more severe HIV, use of acyclovir and H2-blockers, and longer hospital stay. Patients admitted to CCH were taking more antibiotics, had longer hospital stays, and more frequently had a history of C. difficile infection. During the study, two strains (CD1A and CD4) extensively contaminated the CCH environment. However, only CD1A caused an outbreak.

CONCLUSIONS

The C. difficile acquisition rate at CCH was sevenfold higher than that at RPSLMC, and CCH had a more contaminated environment. Differences in patient acquisition rates likely reflect a greater prevalence of traditional C. difficile risk factors and a concurrent outbreak at CCH. Although two strains heavily contaminated the environment at CCH, only one caused an outbreak, suggesting that factors other than the environment are important in initiating C. difficile outbreaks.

Changes in the cause of death among HIV positive subjects across Europe: results from the EuroSIDA study

OBJECTIVES

The causes of death among HIV-positive patients may have changed since the introduction of highly active antiretroviral therapy (HAART). We investigated these changes, patients who died without an AIDS diagnosis and factors relating to pre-AIDS deaths.

METHODS

Analyses of 1826 deaths among EuroSIDA patients, an observational study of 8556 patients. Incidence rates of pre-AIDS deaths were compared to overall rates. Factors relating to pre-AIDS deaths were identified using Cox regression.

RESULTS

Death rates declined from 15.6 to 2.7 per 100 person-years of follow-up (PYFU) between 1994 and 2001. Pre-AIDS incidence declined from 2.4 to 1.1 per 100 PYFU. The ratio of overall to pre-AIDS deaths peaked in 1996 at 8.4 and dropped to < 3 after 1998. The adjusted odds of dying following one AIDS defining event (ADE) increased yearly (odds ratio, 1.53; P < 0.001), conversely the odds of dying following three or more ADE decreased yearly (odds ratio, 0.79; P < 0.001). The proportion of deaths that followed an HIV-related disease decreased by 23% annually; in contrast there was a 32% yearly increase in the proportion of deaths due to known causes other than HIV-related or suicides. Injecting drug users (IDU) were significantly more likely to die before an ADE than homosexuals (relative hazard, 2.97; P < 0.0001) and patients from northern/eastern Europe (relative hazard, 2.01; P < 0.0001) were more likely to die pre-AIDS than southern patients.

CONCLUSIONS

The proportion of pre-AIDS deaths increased from 1994 to 2001; however, the incidence of pre-AIDS deaths and deaths overall declined. IDU and subjects from northern/eastern Europe had an increased risk of pre-AIDS death. HIV-positive patients live longer therefore it is essential to continue to monitor all causes of mortality to identify changes.

Participation in clinical studies among patients infected with HIV-1 in a single treatment centre over 12 years

OBJECTIVE

To examine a complete population of clinic attenders in order to compare the demographics of patients who participated in a clinical study with those who had not. These were subdivided into trials of antivirals, trials for drugs used in opportunistic infections or symptomatic HIV and epidemiological studies. The setting was an established London teaching hospital. All patients diagnosed HIV-positive and attending between July 1983 and 1 January 1999 with one measured CD4 count and at least one follow-up visit were included.

METHODS

The demographics of those participating in a clinical study were compared to those not enrolling using chi2 tests and Wilcoxon tests. Cox models were used to determine factors related to participation in clinical studies.

RESULTS

Data from 2703 patients representing 5342.7 person-years' follow-up were assessed. Median time of follow-up was 23.6 months. Six hundred and eighty-seven (33%) patients had ever participated in a clinical study. After adjustment for demographic factors in multivariate analysis using Cox models, homosexuals were more likely to participate compared with heterosexuals or injecting drug users (IDU) (P = 0.0035 and P = 0.0001, respectively). Women were more likely to enter a study (P = 0.02) and there was no difference between Caucasians and black Africans (P = 0.35). Between the three types of studies few differences were seen.

CONCLUSION

High rates of participation in clinical trials and epidemiological studies were seen in this cohort. In keeping with other studies, homosexual men were well represented but IDU were under-represented. However, women and black African patients showed good uptake of all clinical studies. Hence in this population there is some success in targeting representative groups to participate in clinical studies, but more effort needs to be made with IDU.

AIDS across Europe, 1994-98: the EuroSIDA study

BACKGROUND

The clinical presentation of HIV-1 related diseases could have changed after the introduction of highly active antiretroviral treatment (HAART). We aimed to assess changes over time in the incidence of ADIs overall and within CD4 lymphocyte count strata, the relationship with treatment and degree of immunodeficiency at diagnosis of ADIs.

METHODS

We did a prospective observational multicentre study of over 7300 patients in 52 European HIV-1 outpatient clinics. Incidence rates per 100 patient-years of observation were calculated.

FINDINGS

In total, we recorded 1667 new ADIs; the incidence of ADIs declined from 30.7 per 100 patient-years of observation during 1994 (95% CI 28.0-33.4) to 2.5 per 100 patient-years of observation during 1998 (95% CI 2.0-3.0, p<0.0001, test for trend). Median CD4 lymphocyte count at diagnosis of a new ADI increased from 28 cells/microL to 125 cells/microL between 1994 and 1998 (p<0.0001), yet a steep decline in the rate of ADIs was seen after stratification by latest CD4 lymphocyte count within each year (< or = 50, 51-200, and > 200 cells/microL). Patients on HAART had a lower rate of ADIs than patients not on this treatment within each CD4 lymphocyte count strata. The proportion of ADIs attributable to cytomegalovirus retinitis and Mycobacterium avium complex declined over time (p=0.0058 and 0.0022, respectively), whereas the proportion of diagnoses attributable to non-Hodgkin lymphoma has increased (p<0.0001). In 1994, less than 4% of ADIs were non-Hodgkin lymphoma, in 1998 the proportion was almost 16%. This condition has become one of the most common ADIs in patients on HAART.

INTERPRETATION

Our findings lend support to the idea that treatment regimens can lower the incidence of ADIs. The immediate risk of an ADI for a given CD4 lymphocyte count has declined over time and is lower among patients on HAART. Long-term follow-up of patients on combination treatment is essential to monitor the incidence of new and emerging diagnoses.

Economic methods for measuring the quality of life associated with HIV infection

BACKGROUND

Quality of life is measured as utilities for cost-effectiveness analyses.

OBJECTIVE

To test the adequacy of three common utility elicitation methods for individuals with Human Immunodeficiency Virus (HIV) disease.

MEASUREMENTS

HIV-positive participants (n = 75) rated three standardized health states (symptomatic HIV infection, minor AIDS defining illness, and major AIDS defining illness) with two utility elicitation methods (Standard Gamble [SG], and Time Trade-off [TTO]) and one value method (Visual Analog [VA]). Participants also rated their own health with one utility method (Health Utilities Index [HUI]) and one conventional quality of life method (Medical Outcomes Study--HIV Health Survey [MOS-HIV]).

RESULTS

For all states, SG and TTO scores ranged from near 0.00 (equivalent to death) to 1.00 (best possible quality of life). Mean scores for symptomatic HIV were similar with the SG (0.80) and TTO (0.81) but higher than with the VA (0.70). Similar results were observed for minor AIDS defining illnesses (0.65, 0.65, 0.46 respectively) and major AIDS defining illnesses (0.42, 0.44, 0.25 respectively). Discrepant SG and TTO scores were observed in many individuals and were not explained by demographic characteristics. As expected, HUI scores of an individual's own health were related to the disease state. Four of ten MOS-HIV subscales (overall health, physical functioning, role functioning, and pain) were also related to disease state. HUI scores were correlated with the MOS-HIV score for overall health and for all MOS-HIV subscales except health transition.

CONCLUSIONS

Mean utility scores for HIV-related health states elicited by the Standard Gamble and Time Trade-off were similar but a large degree of individual variation persists. Economic methods provide imprecise estimates of the quality of life associated with HIV infection.

Distribution of CD4+ T-lymphocytes levels in patients with clinical symptoms of AIDS in three west African countries

OBJECTIVES

To study the CD4 T-lymphocyte distribution in patients with clinical signs suggestive of AIDS in West Africa.

DESIGN AND METHODS

Selected patients had clinical AIDS, according to the WHO clinical definition of AIDS in Africa. Serum samples were tested for the presence of HIV antibodies with two different enzyme immunoassays (EIA), and whole blood was used to determine the CD4 lymphocyte levels of each patient, using the TRAx CD4 Test Kit.

RESULTS

In patients with AIDS, the mean CD4+ cell level was 466/microliter; 34% of patients had less than 200/microliter and 62.1% less than 400/microliter. In patients with clinical AIDS but without HIV antibodies, the mean CD4+ cell level was 807/microliter; with 4% below 200/microliter and 14.7% below 400/microliter. The optimal CD4+ cell cut-off between the two groups of patients (with and without antibody to HIV) was 400/microliter.

CONCLUSIONS

The mean CD4 cell levels of AIDS patients was more than twice the 200 CD4+ cells/microliter which, alone or associated with clinical criteria is used to differentiate HIV seropositive patients with and without AIDS. A cut-off of 400 T-lymphocyte equivalents per microlitre (TLE/microliter) will be more appropriate. Only 4% of the anti-HIV negative patients had < 200 CD4 TLE/microliter, and could be infected with unknown immunodeficiency viruses.

Lymphomas and reactive lymphoid lesions in HIV infection

Infection by the human immunodeficiency virus (HIV) causes depletion of CD4-positive lymphocytes with consequent immunodeficiency. HIV infection also causes, by direct or indirect mechanisms, both reactive and neoplastic changes in lymphoid tissues. In primary infection reactive changes are a direct response to HIV. Later in the course of the disease there are reactive changes in lymph nodes and extranodal lymphoid tissues which are likely to be largely an indirect effect of HIV infection, being a response to opportunistic infection by other organisms. There is also an increased incidence of autoimmune phenomena in HIV-infected subjects which is likely to be consequent, at least in part, on impaired control of the proliferation of self-reactive B-cell clones. A second mechanism of immune damage of blood cells, probably operating in the case of HIV-related immune thrombocytopenic purpura, is that of cellular damage by immune complexes containing antiviral antibodies. Lymphoid neoplasms associated with HIV infection include non-Hodgkin's lymphoma, Hodgkin's disease and, uncommonly, plasma cell dyscrasias. HIV-associated lymphomas have distinct clinicopathological features and generally a poor prognosis. As for reactive lymphoid lesions, induction of neoplasia is likely, in the majority of cases, to be an indirect rather than a direct effect of the virus. The combination of chronic B-cell stimulation and impaired T-cell function is important, and interaction of lymphoid cells with virus-infected stromal cells may also play a role. Infection by oncogenic viruses such as the Epstein-Barr virus and human herpes virus 8 is also aetiologically important. In rare cases of T-cell lymphoma, HIV may be directly oncogenic.

Preventing Mycobacterium avium complex in patients who are using protease inhibitors: a cost-effectiveness analysis

BACKGROUND

Practice guidelines recommending Mycobacterium avium complex (MAC) prophylaxis for patients with HIV disease were based on clinical trials in which individuals did not receive protease inhibitors.

OBJECTIVE

To estimate the cost-effectiveness of strategies for MAC prophylaxis in patients whose treatment regimen includes protease inhibitors.

DESIGN

Decision analysis with Markov modelling of the natural history of advanced HIV disease. Five strategies were evaluated: no prophylaxis, azithromycin, rifabutin, clarithromycin and a combination of azithromycin plus rifabutin.

MAIN OUTCOME MEASURES

Survival, quality of life, quality-adjusted survival, health care costs and marginal cost-effectiveness ratios.

RESULTS

Compared with no prophylaxis, rifabutin increased life expectancy from 78 to 80 months, increased quality-adjusted life expectancy from 50 to 52 quality-adjusted months and increased health care costs from $233000 to $239800. Ignoring time discounting and quality of life, the cost-effectiveness of rifabutin relative to no prophylaxis was $44300 per life year. Adjusting for time discounting and quality of life, the cost-effectiveness of rifabutin relative to no prophylaxis was $41500 per quality-adjusted life year (QALY). In comparison with rifabutin, azithromycin was associated with increased survival, increased costs and an incremental cost-effectiveness ratio of $54300 per QALY. In sensitivity analyses, prophylaxis remained economically attractive unless the lifetime chance of being diagnosed with MAC was less than 20%, the rate of CD4 count decline was less than 10 x 10(6) cells/l per year, or the CD4 count was greater than 50 x 10(6) cells/l.

CONCLUSION

MAC prophylaxis increases quality-adjusted survival at a reasonable cost, even in patients using protease inhibitors. When not contraindicated, starting azithromycin or rifabutin when the patient's CD4 count is between 50 and 75 x 10(6) cells/l is the most cost-effective strategy. The main determinants of cost-effectiveness are CD4 count, viral load, place of residence and patient preference.

Predicting outcomes in HIV-infected veterans: II. Survival after AIDS

This article (Part II) and the preceding article (Part I) report the development of two clinical staging systems for HIV-infected individuals. The objective of the research reported here (Part II) was to construct a clinical staging system to predict survival in patients with AIDS. We analyzed data from VA Cooperative Study Number 298, a multicenter, double-blind, randomized trial that compared immediate versus deferred zidovudine therapy in HIV-infected individuals. Baseline variables obtained at the onset of AIDS in 204 individuals were tested in univariate Cox regression for their relationship to survival, and those that appeared predictive were examined in multivariable analysis. Based on these analyses, we constructed a new AIDS Clinical Staging System. The system is based on age, CD4+ cell count, type of first AIDS-defining condition, and functional status. The stages of the system were significant predictors of survival (p = 0.0001, log-rank test). In conclusion, valid, simple clinical staging systems for patients with AIDS can be developed based on a few variables that are readily available in clinical settings.

The impact of high-risk patients on the results of clinical trials

The results of clinical trials may not reflect equally the experiences of all their individual participants. By modeling populations where patients have very diverse baseline risks of suffering an event of interest, it can be seen that very sick patients of high risk become the major determinants of how many events occur in the whole population, even though they may represent only a small minority. Human immunodeficiency virus-related trials and trials of magnesium in acute myocardial infarction are analyzed. When the benefit or toxicity from a treatment varies with the baseline risk of each patient, the treatment effect may be markedly different in populations with a different representation of high- and low-risk patients. The results of small clinical trials studying heterogeneous populations with binary outcomes depend on the sampling and outcomes of very few high risk participants. Conversely, mega-trials studying homogeneous populations would miss subgroups or individuals with diverse treatment responses. In both cases, aggregate trial results may be misleading for the care of many individuals.

Trends in incidence of AIDS illnesses in Australia from 1983 to 1994: the Australian AIDS cohort

To assess time trends in incidence of AIDS illnesses in Australia, a retrospective cohort of people diagnosed with AIDS from January 1, 1983 to December 31, 1994 in three HIV medicine units in Sydney, Melbourne, and Perth was established. Data on initial and subsequent AIDS illnesses were available for 2580 AIDS cases, or 45% of Australian AIDS notifications over the study period. Males represented 97.2% of the cohort, and HIV exposure category was homosexual contact for 89.9%. Subcohorts were formed by interval of AIDS diagnosis: 1983 through 1987, 1988 through 1990, and 1991 through 1994, with estimation of cumulative risk for each AIDS illness by the Kaplan-Meier method. The cumulative risk declined for Pneumocystis carinii pneumonia (PCP) (p < 0.0001) and for Kaposi's sarcoma (KS) (p < 0.0001); PCP cumulative risk estimates 2 years following AIDS diagnosis were 70% for people diagnosed with AIDS in 1983 through 1987 and 48% in 1991 through 1994, and KS cumulative risk estimates 2 years following AIDS diagnosis were 44% in 1983 through 1987 and 32% in 1991 through 1994. In contrast, cumulative risk increased from 34% to 40% for cytomegalovirus (CMV) disease (p = 0.005), from 47% to 50% for Mycobacterium avium complex (MAC) (p < 0.0001), and from 26% to 33% for esophageal candidiasis (p < 0.0001). Corresponding to this changing spectrum of AIDS illness has been an increase in severity of immunodeficiency at AIDS, with median CD4 cell count declining from 54 cells/mm3 in 1983 through 1987 to 34/mm3 in 1991 through 1994 (p = 0.002).

Survival after AIDS diagnosis in a cohort of hemophilia patients. Multicenter Hemophilia Cohort Study

We studied factors affecting survival after the diagnosis of AIDS in a cohort of 1253 patients with hemophilia. The nature of the AIDS-defining condition was found to be as important as age at seroconversion and CD4+ lymphocyte level in predicting survival. A multivariate analysis yielded estimates of median survival for groups defined by age at seroconversion (0 through 15, 16 through 69), CD4+ lymphocyte count (<100 cells/microl versus > or = 100 cells/microl), and 10 AIDS-defining disease groups. Estimates of median survival after a single AIDS-defining condition ranged from 3 to 51 months, depending on the diseases. Median survival after a second AIDS-defining condition was about 1.5- to 2.0-fold shorter than after an initial, isolated AIDS-defining condition. HIV-related neurologic disease (i.e., AIDS dementia complex or multifocal leukoencephalopathy) was a notable exception. It correlated with the shortest estimates of median survival (3 to 9 months), and this poor prognosis was no worse for patients who had a second AIDS-defining condition. The results of this analysis were consistent in most respects with other published analyses of factors affecting survival. These findings may be useful in the clinical care of persons with AIDS and in estimating the number of persons alive who have had a particular AIDS-defining disease.

Survival and treatment of AIDS patients 1984-1993: experience of a smaller east London HIV centre

OBJECTIVE

To assess changes in survival from diagnosis of AIDS for patients managed in a small East London HIV clinic and the impact of therapeutic interventions on these survival patterns.

DESIGN

Prospective observational study.

SETTING

Grahame Hayton Unit, Royal London Hospital.

SUBJECTS

156 AIDS patients managed between 1984 and 1993.

MAIN OUTCOME MEASURE

Survival from diagnosis of AIDS.

RESULTS

Median survival for those diagnosed with AIDS before 1 January 1987 was 9.4 months compared with 27.2 months after 1 January 1987 (logrank chi 2 = 10.3, p = 0.001): CD4 count at time of AIDS and treatment with zidovudine or PCP prophylaxis were significantly associated with survival from time of AIDS. Of the 156 AIDS patients, 93 had been treated with zidovudine sometime during their follow up, 60 had received primary and 50 secondary Pneumocystis carinii pneumonia (PCP) prophylaxis. After controlling for gender, sexual orientation, age at time of AIDS, CD4 count at time of AIDS, diagnosis when first presenting to the clinic (AIDS/non-AIDS) and year of AIDS diagnosis, all patients who received either zidovudine or PCP prophylaxis had significant reductions in the risk of dying compared with those who received neither PCP prophylaxis nor zidovudine: a reduction in risk of dying between 71% (95% CI 40% to 86%) and 83% (95% CI 50% to 94%) was observed depending on the combination of zidovudine and PCP prophylaxis.

CONCLUSION

A debate is currently taking place about the format and value of HIV service provision with increasing numbers of HIV infected individuals managed at smaller HIV clinics. Larger clinics concentrate clinical expertise on a single site and facilitate clinical trials. Smaller well run HIV units staffed by competent health professionals not only provide clinical outcomes similar to those obtained in the larger centres, but may also allow a more informal and intimate setting for HIV infected individuals who want to be treated nearer their area of residence.