Determinants of geographic mobility among participants in a population-based HIV/AIDS drug treatment program

This study was undertaken to determine the geographic distribution and patterns of migration of persons with HIV in British Columbia. Our analysis was restricted to all HIV-positive men and women aged 18 years and over who had completed a participant survey and were enrolled in the HIV/AIDS Drug Treatment Program between September 1992 and September 1997. Patterns of migration were determined by examining participants whose postal code changed between July 1995 and September 1997. Statistical analysis were carried out using both parametric and non-parametric methodologies. Stepwise logistic regression was used to determine baseline predictors of migration. The final multivariate model revealed that residing in a census subdivision with a population less than 100,000, being heterosexual, acquiring HIV through intravenous drug use, and the absence of AIDS at baseline were all independently associated with moving census subdivisions during the period of observation. In summary, our analyses demonstrate the need for the continued study of the evolving geography and migration patterns of persons with HIV.

Human immunodeficiency virus-infected persons with mutations conferring resistance to zidovudine show reduced virologic responses to hydroxyurea and stavudine-lamivudine

The baseline predictors of poor virologic response (<0.5 log decrease in plasma virus load) were examined in two 1996 pilot trials of combination nucleoside-analogue therapy. One trial examined the addition of hydroxyurea to didanosine therapy; the other examined stavudine-lamivudine in combination. In both, predictors of virologic response included the presence of mutations associated with zidovudine resistance. For hydroxyurea, the odds ratio (OR) of failure to achieve a short-term (4 weeks) virologic response in a bivariate logistic regression model was 30.8 (95% confidence interval [CI], 1.75-543; P=.02) for use of lower dose hydroxyurea (500 mg/day) and 14.7 (95% CI, 1.1-200; P=.04) for the presence of a zidovudine-related mutation. For the stavudine-lamivudine study, the OR of failure to achieve a virologic response at 4 weeks in a multivariate logistic regression model was 23 (95% CI, 2.7-199; P=.004) for the presence of a mutation at codon 215.

Antiretroviral therapy in adults: updated recommendations of the International AIDS Society-USA Panel

OBJECTIVE

To update recommendations for antiretroviral therapy for adult human immunodeficiency virus type 1 (HIV-1) infection, based on new information and drugs that are available.

PARTICIPANTS

A 17-member international physician panel with antiretroviral research and HIV patient care experience initially convened by the International AIDS Society-USA in December 1995.

EVIDENCE

Available clinical and basic science data including phase 3 controlled trials; data on clinical, virologic, and immunologic end points; research conference reports; HIV pathogenesis data; and panel expert opinion. Recommendations were limited to therapies available (US Food and Drug Administration approved) in 1999.

CONSENSUS PROCESS

The panel assesses new research reports and interim results and regularly meets to consider how the new data affect therapy recommendations. Recommendations are updated via full-panel consensus. Guidelines are presented as recommendations if the supporting evidence warrants routine use in the particular situation and as considerations if data are preliminary or incomplete but suggestive.

CONCLUSIONS

The availability of new antiretroviral drugs has expanded treatment choices. The importance of adherence, emerging long-term complications of therapy, recognition and management of antiretroviral failure, and new monitoring tools are addressed. Optimal care requires individualized management and ongoing attention to relevant scientific and clinical information in the field.

The impact of zidovudine on dementia-free survival in a population of HIV-positive men and women on antiretroviral therapy

Our objective was to characterize the effect of zidovudine therapy on AIDS dementia complex (dementia) free survival among HIV-infected men and women in a population-based cohort with free access to antiretroviral therapy in the province of British Columbia. Time to diagnosis of dementia among individuals was examined on the basis of zidovudine duration, CD4+ cell count at first treatment, gender, and transmission group [men having sex with men (MSM), intravenous drug users (IDU), heterosexuals]. We restricted the analysis to subjects with CD4+ cells counts within 12 months prior to treatment start date. Among 641 participants eligible for analysis, median duration of follow-up was 3.6 years, under which 86 (9.3%) events of dementia occurred. Participants were less likely to develop dementia with: increased zidovudine exposure (OR=0.26, 95% CI: 0.14-0.49), at least 260 CD4+ cells/mm3 (median) (OR=0.52, 95% CI: 0.34-0.78), and MSM risk group (OR=0.57, 95% CI: 0.35-0.94). Those infected through heterosexual contact had an increased risk (RR=2.04, 95% CI: 1.02-4.07). Using Cox's proportional hazards model, controlling for CD4+ cell count at treatment start date, independent predictors of dementia-free survival were: duration of zidovudine (OR=0.28, 95% CI: 0.15-0.52) and MSM transmission group (OR=0.61, 95% CI: 0.37-1.00). In this observational treatment cohort, factors associated with dementia-free survival include duration of zidovudine (AZT) therapy and MSM transmission group. It is not clear from these data whether the AZT protective effect is exclusive to this agent or whether other therapies might offer a similar protective effect.

Meta-analysis of two randomized controlled trials comparing combined zidovudine and didanosine therapy with combined zidovudine, didanosine, and nevirapine therapy in patients with HIV. INCAS study team

OBJECTIVES

To extend the range of CD4 counts in which a plasma viral load nadir (pVL) <20 copies/ml was known to be predictive of the duration of virologic response. To determine whether baseline pVL is predictive of virologic response during the study periods.

METHODS

A meta-analysis was conducted of the original individual patient data from two randomized controlled trials comparing zidovudine (ZDV)/didanosine (ddI) with ZDV/ddI/nevirapine (NVP).

RESULTS

In total, 87 patients received ZDV/ddI and 83 received ZDV/ddI/NVP. Study subjects on triple therapy with baseline pVL <100,000 copies/ml were more likely to achieve a pVL <400 copies/ml (odds ratio [OR] = 2.49; p = .02) and <20 copies/ml (OR = 4.76; p = .001) during the trial than those with baseline pVL > 100,000 copies/ml. Among triple therapy patients, the relative risk of virologic failure was higher for patients with higher baseline pVL (rate ratio [RR] = 2.51/log10 copies/ ml; p = .01), after controlling for compliance and pVL nadir. The relative risks of virologic failure associated with pVL nadir <20 copies/ml and between 21 and 400 copies/ml were .04 (p = .0001) and .56 (p = .26), respectively, compared with patients with a pVL nadir >400 copies/ml.

CONCLUSIONS

We have extended our earlier results that achieving a pVL nadir <20 copies/ml is important for maintaining virologic suppression. In particular, we have demonstrated that a pVL nadir <20 copies/ml is at least fivefold more protective against virologic failure than achieving a pVL nadir between 20 and 400 copies/ml. Baseline pVL is significantly associated with the probability of achieving and sustaining virologic suppression.

Baseline HIV drug resistance profile predicts response to ritonavir-saquinavir protease inhibitor therapy in a community setting

OBJECTIVE

To determine whether baseline drug resistance assays could help to predict treatment failure with the protease inhibitor combination ritonavir-saquinavir.

METHODS

Baseline HIV-1 drug resistance was determined for 76 consecutive patients who started treatment with the dual protease inhibitor combination ritonavir-saquinavir between September 1996 and June 1997 either alone or in combination with other antiviral agents. Resistance to 10 different antiviral agents was assessed by both phenotype (Virco Antivirogram) and genotype (Vircogen).

RESULTS

Resistance inferred from viral genotype was similar to measured phenotypic resistance for both ritonavir and saquinavir (P<0.01). Baseline drug resistance phenotype was predictive of poor virological response to this dual protease inhibitor combination, despite the confounding effects of other antivirals. Patients were at least four times less likely to achieve a 0.5 log10 decrease in plasma HIV RNA viral load if their viral isolates were resistant to ritonavir or saquinavir. Patients classified as resistant to either drug using either method had median decreases in plasma viral load of 0.05 log10 HIV RNA copies/ml or less, compared to >0.8 log10 for those with sensitive virus. Patients resistant to both drugs never achieved plasma viral loads <100000 copies/ml. As little as fourfold increases in baseline resistance appeared to be sufficient to compromise even dual protease inhibitor therapy.

CONCLUSION

Baseline resistance to ritonavir or saquinavir or both was associated with a poor antiviral response. Our data suggest that the measurement of drug resistance may assist in optimizing antiretroviral therapy in the clinic.

Suppression of plasma virus load below the detection limit of a human immunodeficiency virus kit is associated with longer virologic response than suppression below the limit of quantitation

Suppression of human immunodeficiency virus type 1 plasma virus load (PVL) to <20 copies/mL is associated with a longer virologic response after initiation of antiretroviral therapy. The relationship between duration of virologic response and PVL nadir according to a less sensitive assay was explored. When compared with subjects with a PVL nadir >500 copies/mL, the relative risks of PVL rising above 1000 copies/mL for participants in the INCAS trial and the British Columbia Drug Treatment Program with a PVL nadir below the limit of detection (LOD) were 0.04 (95% confidence interval [CI], 0.02-0.09) and 0.06 (95% CI, 0.03-0.12), respectively. The corresponding relative risks for persons with a detectable but not quantifiable PVL nadir were 0.25 (95% CI, 0.13-0.50) and 0.54 (95% CI, 0.25-1.19). The relative risks of virologic failure associated with a PVL nadir detectable but not quantifiable and a PVL nadir below the LOD were statistically different (P<.0001) in both data sets.

Effects of anticoagulant, processing delay, and assay method (branched DNA versus reverse transcriptase PCR) on measurement of human immunodeficiency virus type 1 RNA levels in plasma

We conducted two studies to determine the potential influence of delays in blood processing, type of anticoagulant, and assay method on human immunodeficiency virus type 1 (HIV-1) RNA levels in plasma. The first was an experimental study in which heparin- and EDTA-anticoagulated blood samples were collected from 101 HIV-positive individuals and processed to plasma after delays of 2, 6, and 18 h. HIV-1 RNA levels in each sample were then measured by both branched-DNA (bDNA) and reverse transcriptase PCR (RT-PCR) assays. Compared to samples processed within 2 h, the loss (decay) of HIV-1 RNA in heparinized blood was significant (P < 0.05) but small after 6 h (bDNA assay, -0.12 log(10) copies/ml; RT-PCR, -0.05 log(10) copies/ml) and after 18 h (bDNA assay, -0.27 log(10) copies/ml; RT-PCR, -0.15 log(10) copies/ml). Decay in EDTA-anticoagulated blood was not significant after 6 h (bDNA assay, -0.002 log(10) copies/ml; RT-PCR, -0.02 log(10) copies/ml), but it was after 18 h (bDNA assay, -0.09 log(10) copies/ml; RT-PCR, -0.09 log(10) copies/ml). Only 4% of samples processed after 6 h lost more than 50% (>/=0.3 log(10) copies/ml) of the HIV-1 RNA, regardless of the anticoagulant or the assay that was used. The second study compared HIV-1 RNA levels in samples from the Multicenter AIDS Cohort Study (MACS; samples were collected in heparin-containing tubes in 1985, had a 6-h average processing delay, and were assayed by bDNA assay) and the British Columbia Drug Treatment Program (BCDTP) (collected in EDTA- or acid citrate dextrose-containing tubes in 1996 and 1997, had a 2-h maximum processing delay, and were assayed by RT-PCR). HIV-1 RNA levels in samples from the two cohorts were not significantly different after adjusting for CD4(+)-cell count and converting bDNA assay values to those corresponding to the RT-PCR results. In summary, the decay of HIV-1 RNA measured in heparinized blood after 6 h was small (-0.05 to -0.12 log(10) copies/ml), and the minor impact of this decay on HIV-1 RNA concentrations in archived plasma samples of the MACS was confirmed by the similarity of CD4(+)-cell counts and assay-adjusted HIV-1 RNA concentrations in the MACS and BCDTP.

Prevalence of primary HIV drug resistance among seroconverters during an explosive outbreak of HIV infection among injecting drug users

OBJECTIVES

This study examined the frequency of transmission of drug resistant HIV in the population of injecting drug users (IDU) in Vancouver, Canada during a period of particularly high virus transmission.

DESIGN

All subjects enrolled in the Vancouver Injection Drug Users Study who seroconverted from HIV negative to positive status (n = 61) between December 1996 and February 1998 were eligible for analysis. The first seropositive sample from 57 individuals with plasma samples available was analyzed for resistance to antiretroviral agents by population based sequencing of the HIV protease and reverse transcriptase genes.

METHODS

Plasma viral RNA was extracted and the viral reverse transcriptase and protease regions were amplified by nested reverse transcription-PCR. The presence of mutations associated with antiretroviral drug resistance was assessed by automated sequence analysis.

RESULTS

Protease and reverse transcriptase sequences were successfully obtained from the 57 recent seroconverters. No cases of transmission of variants associated with significant resistance to protease inhibitors or nucleoside and non-nucleosides reverse transcriptase inhibitors were detected.

CONCLUSION

The frequency of transmission of drug resistant HIV amongst these recently infected IDU is extremely low, with no protease or reverse transcriptase inhibitor resistant strains detected soon after seroconversion. The data provide no rationale for withholding treatment from this already marginalized population.

Rate of HIV-1 RNA rebound upon stopping antiretroviral therapy

OBJECTIVE

To determine the rate of plasma HIV-1 RNA rebound in patients stopping highly active antiretroviral therapy (HAART) after achieving undetectable viral load.

DESIGN

Sequential plasma HIV RNA levels were measured in six patients during the 21 days following withdrawal from HAART.

METHODS

Plasma samples were obtained from six patients who chose to withdraw from HAART because of lipodystrophy, narcotic overdose, insomnia and/or high blood pressure. Longitudinal plasma viral load was determined in triplicate upon stopping therapy.

RESULTS

All patients had plasma viral loads below 50 HIV RNA copies/ml at the time of stopping therapy and had had levels below 500 copies/ml for a median of 390 days (range 39-542 days). Plasma HIV rebound upon stopping therapy was rapid (median increase 0.2 log/day; range 0.15-0.42 log/day) and initially appeared to follow first-order kinetics. Plasma HIV RNA levels returned to greater than 500 copies/ml within 6 to 15 days (median 10 days) and approached or exceeded pre-therapy levels in all patients within 21 days of stopping therapy. Extrapolating backwards to the time at which individuals stopped therapy suggested that patients had tens of thousands of total body plasma HIV RNA copies despite having 'undetectable' plasma HIV RNA.

CONCLUSIONS

HIV RNA in plasma rebounds within days of stopping antiretroviral therapy. A considerable burden of total body plasma HIV RNA likely remains even during effective HAART therapy.

Determinants of short- and long-term outcome in patients with respiratory failure caused by AIDS-related Pneumocystis carinii pneumonia

OBJECTIVES

To determine (1) predictors of in-hospital mortality and long-term survival in patients with acute respiratory failure (ARF) caused by acquired immunodeficiency syndrome-related Pneumocystis carinii pneumonia (PCP) and (2) long-term survival for patients with ARF relative to those without ARF.

METHODS

A retrospective medical chart review was conducted of all cases of PCP-related ARF for which the patient was admitted to the intensive care unit of a single tertiary care institution between 1991 and 1996. Data were extracted regarding physiologic scores, relevant laboratory values, and duration of previous maximal therapy with combined anti-PCP agents and corticosteroids at entry to the intensive care unit. Duration of survival was determined by Kaplan-Meier methods from date of first hospital admission and compared for patients with and without ARF.

RESULTS

There were 41 admissions to the intensive care unit among 39 patients, with 56.4% in-hospital mortality. Higher physiologic scores (Acute Physiology and Chronic Health Evaluation II [APACHE II], Acute Lung Injury, and modified Multisystem Organ Failure scores) were predictive of in-hospital mortality. Duration of previous maximal therapy also predicted in-hospital mortality (45% for patients with <5 days of previous maximal therapy vs 88% for those with > or =5 days of previous maximal therapy; P = .03). Combining physiologic scores and duration of previous maximal therapy enhanced prediction of in-hospital mortality. There was no difference in long-term survival between patients with PCP with ARF and those without ARF (P = .80), and baseline characteristics did not predict long-term survival.

CONCLUSIONS

In-hospital mortality of patients with acquired immunodeficiency syndrome-related PCP and ARF is predicted by duration of previous maximal therapy and physiologic scores, and their combination enhances predictive accuracy. Long-term survival of patients with ARF caused by PCP is comparable to that of patients with PCP who do not develop ARF, and determinants of in-hospital mortality do not predict long-term survival.

Improved survival among HIV-infected patients after initiation of triple-drug antiretroviral regimens

BACKGROUND

The efficacy of triple-drug antiretroviral regimens in the treatment of patients infected with HIV has been established in several randomized clinical trials. However, the effectiveness of these new regimens in patient populations outside clinical trials remain unproven. This study compared mortality and AIDS-free survival among HIV-infected patients in British Columbia who were treated with double- and triple-drug regimens.

METHODS

The authors used a prospective, population-based cohort design to study a population of HIV-positive men and women 18 years or older for whom antiretroviral therapy was first prescribed between Oct. 1, 1994, and Dec. 31, 1996; all patients were from British Columbia. Rates of progression from the initiation of antiretroviral therapy to death or to diagnosis of primary AIDS were determined for patients who initially received an ERA-II regimen (2 nucleoside analogue reverse transcriptase inhibitors [NRTIs] including lamivudine or stavudine, or both) and for those who initially received an ERA-III regimen (triple-drug regimen consisting of 2 NRTIs and a protease inhibitor [indinavir, ritonavir or saquinavir] or a non-NRTI [nevirapine]).

RESULTS

A total of 500 men and women (312 receiving an ERA-III regimen and 188 an ERA-III regimen) were eligible. Patients in the ERA-III group survived significantly longer than those in the ERA-II group. As of Dec. 31, 1997, 40 patients had died (35 in the ERA-II group and 5 in the ERA-III group), for a crude mortality rate of 8.0%. The cumulative mortality rates at 12 months were 7.4% (95% confidence interval [CI] 5.9% to 8.9%) for patients in the ERA-II group and 1.6% (95% CI 0.7% to 2.5%) for those in the ERA-III group (log rank p = 0.003). The likelihood of death was more than 3 times higher among patients in the ERA-II group (mortality risk ratio 3.82 [95% CI 1.48% to 9.84], p = 0.006). After adjustment for prophylaxis for Pneumocystis carinii pneumonia or Mycobacterium avium infection, AIDS diagnosis, CD4+ cell count, sex and age at initiation of therapy, the likelihood of death among patients in the ERA-II group was 3.21 times higher (95% CI 1.24 to 8.30, p = 0.016) than in the ERA-III group. Cumulative rates of progression to AIDS or death at 12 months were 9.6% (95% CI 7.7% to 11.5%) in the ERA-II group and 3.3% (95% CI 1.8% to 4.8%) in the ERA-III group (log rank p = 0.006). After adjustment for prognostic variables (prophylaxis for P. carinii pneumonia or M. avium infection, CD4+ cell count, sex and age at initiation of treatment), the likelihood of progression to AIDS or death at 12 months among patients in the ERA-II group was 2.37 times higher (95% CI 1.04 to 5.38, p = 0.040) than in the ERA-III group.

INTERPRETATION

This population-based cohort study confirms that patients initially treated with a triple-drug antiretroviral regimen comprising 2 NRTIs plus protease inhibitor or a non-NRTI have a lower risk of morbidity and death than patients treated exclusively with 2 NRTIs.

Antiretroviral therapy: 'the state of the art'

The field of antiretroviral therapy is evolving at a very rapid pace. At this time, the initiation and optimization of antiretroviral therapy is based on serial plasma viral load determinations which aim to suppress viral replication to as low as possible for as long as possible, thus preventing disease progression. Currently available antiretrovirals require combination therapy with at least three agents to achieve this goal. Increasing availability of newer and more potent antiretroviral regimens will continue to enhance and simplify the number of therapeutic options available in the not too distant future.

Immune restoration does not invariably occur following long-term HIV-1 suppression during antiretroviral therapy. INCAS Study Group

BACKGROUND

Current antiretroviral treatment can induce significant and sustained virological and immunological responses in HIV-1-infected persons over at least the short- to mid-term.

OBJECTIVES

In this study, long-term immune reconstitution was investigated during highly active antiretroviral therapy.

METHODS

Patients enrolled in the INCAS study in The Netherlands were treated for 102 weeks (range 52-144 weeks) with nevirapine (NVP) + zidovudine (ZDV) (n = 9), didanosine (ddl) + ZDV (n = 10), or NVP + ddl + ZDV (n = 10). Memory and naïve CD4+ and CD8+ T cells were measured using CD45RA and CD27 monoclonal antibodies (mAb), T-cell function was assayed by CD3 + CD28 mAb stimulation, and plasma HIV-1 RNA load was measured by ultra-direct assay (cut-off < 20 copies/ml).

RESULTS

Compared to both double combination regimens the triple combination regimen resulted in the most sustained increase in CD4+ T cells (change in CD4+, + 253 x 10(6) cells/l; standard error, 79 x 10(6) cells/l) and reduction of plasma HIV-1 RNA. In nine patients (31%) (ddl + ZDV, n = 2; NVP + ddl + ZDV, n = 7) plasma HIV-1 RNA levels remained below cut-off for at least 2 years. On average, these long-term virological responders demonstrated a significantly higher increase of naïve and memory CD4+ T cells (P = 0.01 and 0.02, respectively) as compared with patients with a virological failure, and showed improved T-cell function and normalization of the naïve; memory CD8+ T-cell ratio. However, individual virological success or failure did not predict the degree of immunological response. T-cell patterns were independent of baseline CD4+ T-cell count, T-cell function, HIV-1 RNA load or age. Low numbers of naïve CD4+ T cells at baseline resulted in modest long-term naïve T-cell recovery.

CONCLUSIONS

Patients with prolonged undetectable plasma HIV-1 RNA levels during antiretroviral therapy do not invariably show immune restoration. Naïve T-cell recovery in the setting of complete viral suppression is a gradual process, similar to that reported for immune recovery in adults after chemotherapy and bone marrow transplantation.

The incidence and spectrum of AIDS-defining illnesses in persons treated with antiretroviral drugs

The incidence and spectrum of primary AIDS-defining illnesses in human immunodeficiency virus-positive patients receiving antiretroviral drugs may have changed since the introduction of newer antiretroviral agents. We performed a retrospective analysis of patients enrolled in the British Columbia Drug Treatment Program who were ever prescribed antiretroviral drugs between 1 January 1994 and 31 December 1996. Rates were calculated on a 6-month basis. There were 344 AIDS cases diagnosed among 2,533 participants between 1994 and 1996. The incidence of primary AIDS diseases decreased from 1994 to 1996, with a sharp decline in 1995 and 1996. There was no statistically significant change in the incidence of primary AIDS diagnoses relative to one another, and Pneumocystis carinii pneumonia and Kaposi's sarcoma remain the most common AIDS index diagnoses. In patients receiving antiretroviral therapy in the modern era, the incidence of AIDS-defining illnesses has decreased substantially, but the spectrum of AIDS-defining illnesses remains unchanged.

One world, one hope: the cost of providing antiretroviral therapy to all nations

OBJECTIVE

To estimate the potential direct cost of making triple combination antiretroviral therapy widely available to HIV-positive adults and children living in countries throughout the world.

METHODS

For each country, antiretroviral costs were obtained by multiplying the annual cost of triple antiretroviral therapy by the estimated number of HIV-positive persons accessing therapy. Per capita antiretroviral costs were computed by dividing the antiretroviral costs by the country's total population. The potential economic burden was calculated by dividing per capita antiretroviral costs by the gross national product (GNP) per capita. All values are expressed in 1997 US dollars.

RESULTS

The potential cost of making triple combination antiretroviral therapy available to HIV-positive individuals throughout the world was estimated to be over US$ 65.8 billion. By far the greatest financial burden was on sub-Saharan Africa. The highest per capita drug cost in this region would be incurred in the subregions of Southern Africa (US$ 149) followed by East Africa (US$ 116), Middle Africa (US$ 44), and West Africa (US$ 42). In the Americas, subregional data indicated the highest per capita drug cost would be in the Latin Caribbean (US$ 22), followed by the Caribbean (US$ 17), Andean Area (US$ 7), the Southern Cone (US$ 6), North America (US$ 6), and Central American Isthmus (US$ 5). In Asia and Europe the percentage of the GNP necessary to finance drug therapy was less than 1% in most countries examined.

CONCLUSION

Our results demonstrate that the cost of making combination antiretroviral therapy available worldwide would be exceedingly high, especially in countries with limited financial resources.

Estimates of the virological benefit of antiretroviral therapy are both assay- and analysis-dependent

OBJECTIVE

To assess the potential discrepancies in reported changes in plasma viral load (PVL) depending on how values below the detection limit of the assay are handled in the data analysis phase of a randomized controlled clinical trial.

DESIGN

Data from a recently completed clinical trial comparing combinations of zidovudine, didanosine and nevirapine were analysed. In this trial, PVL was measured using an assay with a lower quantification limit of 400 HIV-1 RNA copies/ml initially. All PVL values less than 500 copies/ml were retested with a more sensitive assay with a lower quantification limit of 20 copies/ml.

METHODS

Several summary measures for assessing change in PVL were calculated using three different methods to adjust for PVL values less than the quantification limit of the assay. The differences between these measures were evaluated.

RESULTS

We found that the magnitude of the discrepancy between summary measures used to report changes in PVL depended on the proportion of subjects with PVL less than the quantification limit of the assay, how those observations were handled in the data analysis, and the relative difference between the quantification limits of the conventional and more sensitive assay.

CONCLUSION

The lack of consensus in reporting of PVL data in the literature makes the interpretation of published trial results difficult. In the absence of agreement on the most appropriate summary measure of PVL data, we recommend that all summaries include information on the quantification limit of the assay used, the proportion of observations at or below the quantification limit and how these observations were handled in the data analysis.

Comparison of costs of strategies for measuring levels of human immunodeficiency virus type 1 RNA in plasma by using Amplicor and Ultra Direct assays

The costs of four algorithms for monitoring plasma human immunodeficiency virus type 1 RNA were compared. For patients with strong virologic responses, the use of Ultra Direct exclusively was the cheapest strategy. For patients with weak virologic responses, small savings could be obtained by using Amplicor and retesting only samples with values below 500 copies/ml with Ultra Direct.