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Biomedical subjects

Andrew N Phillips

Publications and source records attributed to Andrew N Phillips.

At least 55 records · Page 3Linked to original sources
PubMed2003

The potential for CD4 cell increases in HIV-positive individuals who control viraemia with highly active antiretroviral therapy.

OBJECTIVES: To study the long-term CD4 cell responses to highly active antiretroviral therapy (HAART) in treatment-naive patients whose viral loads remained below 500 copies/ml for prolonged periods. DESIGN: A total of 237 patients whose viral loads remained below 500 copies/ml for one year or more. Median follow-up was 1.9 years. METHODS: CD4 cell counts were analysed to investigate long-term immunological response using mixed-effects models with the slope allowed to change after 1, 12 and 24 months of HAART. RESULTS: The median baseline CD4 cell count was 175 cells/mm3. After an initial rapid increase in the first month after HAART (97.2 cells/mm3 a month), increases in CD4 cell counts continued less rapidly (11.6 cells/mm3 a month). This increase slowed by 2.4 cells/mm3 a month after one year. CD4 cell counts continued increasing after 2 years, but the rate of increase again slowed (estimated slope at 2 years 5.4 cells/mm3 a month; decrease in slope from year 2 compared with years 1-2 3.7 cell/mm3 a month). A total of 198 out of 211 patients (94%) with measurements at baseline and one year experienced an increase in CD4 cell counts in this interval; 81 and 67% had an increasing slope between 1 and 2 and 2 and 3 years, respectively. By the end of follow-up, CD4 cell counts had increased by 319 cells/mm3, and were more than 500 cells/mm3 in 40% of patients. CONCLUSION: Although the rate of immune recovery slowed after 2 years, CD4 cell counts rose in most and began to return to levels seen in HIV-negative individuals.

Adult↗
PubMed2003

Theoretical rationale for the use of sequential single-drug antiretroviral therapy for treatment of HIV infection.

BACKGROUND: Subpopulations of HIV with mutations associated with resistance to antiretroviral drugs often have reduced replicative capacity, so virus with resistance mutations for all existing and new antiretroviral drugs is likely to be appreciably impaired. Issues of toxicity, quality of life and economics mean that the simultaneous use of all these drugs in combination is unrealistic. We aimed to explore the use of sequential monotherapy regimens using a mathematical model of quasi-species dynamics, to see if these could take advantage of the poor replicative capacity of highly resistant virus. METHODS: We assume for each of seven drugs that a single mutation is associated with the ability to replicate (effective reproductive ratio, R > 1) in the presence of that drug as monotherapy. Parameters included were drug efficacy, the cost of resistance mutations and the number of new target cells arising daily. RESULTS: The use of seven drugs in a daily/weekly sequential monotherapy cycle led to substantial viral suppression (in the presence of all resistant viral subpopulations) for a wider range of parameter values than a continuous five-drug regimen. Although on any one day/week there is a viral subpopulation with R > 1 (e.g. that with resistance only to the current drug), this subpopulation does not have time to grow sufficiently during the short period when that drug is being taken. CONCLUSION: These results provide a rationale for trials of sequential regimens, using as wide a number of drugs with different resistance-associated mutations as possible, as a potential 'resistance-proof' strategy for achieving significant viral load suppression.

Anti-HIV Agents↗
PubMed2003

Virologic, immunologic, and clinical response to highly active antiretroviral therapy: the gender issue revisited.

BACKGROUND: Highly active antiretroviral therapy (HAART) has dramatically improved the prognosis for patients with HIV. There is ongoing debate over a potential gender effect on patient outcome after HAART. METHODS: Individuals were from the EuroSIDA cohort, naive to protease inhibitors and nonnucleoside reverse transcriptase inhibitors, and had at least one viral load and CD4 measurement prior to starting HAART. Endpoints were virologic (time to <500 copies/mL, time to rebound [first of two consecutive viral loads >500 copies/mL]), immunologic (time to a 100/mm cell rise in CD4 count) and clinical (time to new AIDS and death). Hazard ratios (HR), derived using Cox regression models, compared female to male rates of achieving endpoints. RESULTS: Of 2547 patients, 20% (511) were female. Significantly more females than males were nonwhite (24% vs. 10%, p <.001). Males were older (median age 39 vs. 35 years, p <.0001), had lower CD4 counts (211 vs. 240/mm, p =.03), higher viral loads (4.6 vs. 4.4 log copies/mL, p <.0001), were more likely to have a history of AIDS (26% vs. 18%, p <.001) and were more likely to be treatment-naive (34% vs. 29%, p =.03). Adjusted HR for association between gender (comparing females with males) and the outcomes studied were as follows: for reaching <500 copies/mL 0.91 (0.81-1.03, p =.17), rebound 1.17 (0.95-1.44, p =.15), for 100 cell CD4 count rise 1.02 (0.88-1.14, p =.99), for progression to new AIDS 1.12 (0.73-1.71, p =.59) and for time to death 1.15 (0.69-1.92, p =.57). CONCLUSIONS: We found no significant evidence of a gender difference in virologic, immunologic, or clinical outcomes after starting HAART.

Adult↗
PubMed2003

Changes in viral load in people with virological failure who remain on the same HAART regimen.

OBJECTIVES: To assess the rate of change in viral load and CD4 count over time in HIV-infected patients experiencing virological failure on a HAART regimen. DESIGN: Study population included patients from EuroSIDA, a large, multicentre, observational study enrolling HIV-infected patients across Europe. METHODS: Median change in viral load and CD4 count per month were estimated using the viral load and CD4 measurements obtained over a 12-month period after confirmed virological failure between 3 and 4 log10 copies/ml in a population of 488 HIV-infected patients who were left on a failing HAART regimen. RESULTS: The estimated median viral load change in our study population was 0.024 log10 copies/ml per month, statistically different from 0 (P=0.0001). In 20.9% of the patients studied viral load showed a tendency to decrease, in 47.8% showed a tendency to increase by a positive rate no higher than 0.04 log10 copies/ml per month and in the remaining 31.3% showed a tendency to increase by a rate greater than 0.04 log10 copies/ml per month. On average, CD4 counts were estimated to remain stable (decrease at a slow rate of about -0.53 cells/microl per month). CONCLUSIONS: In patients that remained on a stable, but virologically failing HAART regimen (with viral load ranging 1000-10000 copies/ml), the viral load over the ensuing 12-month period increased at a relatively slow rate. In contrast, the CD4 count remained stable, possibly because of partial but sustained viral suppression below the viral load natural set-point. The time-course of selecting more replication-competent virus in patients with virological failure remains to be fully clarified.

Adult↗
PubMed2002

Markers of HIV-1 disease progression in individuals with haemophilia coinfected with hepatitis C virus: a longitudinal study.

BACKGROUND: Low serum albumin concentration is associated with short-term survival in individuals with HIV-1. However, few investigators have assessed whether individuals with a low serum albumin concentration have delayed progression to AIDS, or survive in the long term. We aimed to assess the relation between markers of liver function and progression to AIDS and death in individuals with haemophilia infected with HIV-1 and hepatitis C virus. METHODS: We measured markers of liver function and took CD4 counts every 3 months in 111 patients registered at the Royal Free Hospital Haemophilia Centre, London, UK. HIV RNA concentrations were measured yearly and then every 3-6 months from 1996. We used Cox's regression models to assess the independent prognostic value of these markers for AIDS and death. FINDINGS: As a fixed covariate, albumin concentrations measured shortly after HIV-1 seroconversion were associated with risk of AIDS (relative hazard 0.91 [95% CI 0.84-1.00], p=0.04) and death (0.89 [0.82-0.96], p=0.004) over a 15-year period. These findings were independent of the CD4 count and HIV-1 RNA concentration. As a time-updated covariate, after adjustment for CD4 count and HIV-1 RNA concentrations, albumin was not associated with progression to AIDS (0.96 [0.90-1.01], p=0.13), but was strongly associated with death (0.88 [0.84-0.93], p<0.0001) in the short term. INTERPRETATION: Low concentrations of albumin in individuals infected with HIV-1 could indicate a poor outlook and should therefore prompt concern at any stage of infection.

Acquired Immunodeficiency Syndrome↗
PubMed2002

Human immunodeficiency virus rebound after suppression to <400 copies/mL during initial highly active antiretroviral therapy regimens, according to prior nucleoside experience and duration of suppression.

This study evaluated 1433 human immunodeficiency virus (HIV)-infected patients starting highly active antiretroviral therapy (HAART), 409 (28%) of whom had prior nucleoside experience and achieved an HIV load of <400 copies/mL by 24 weeks of therapy. Three hundred seven patients experienced virus rebound during a total of 2773.3 person-years of follow-up. There was a higher rate of virus rebound among the patients with pre-HAART nucleoside experience (relative hazard [RH], 2.86; 95% confidence interval, 2.22-3.84; P<.0001) and a decreasing rate of virus rebound with increasing duration of virus suppression (i.e., time since achieving a virus load of <400 HIV RNA copies/mL) among both the nucleoside-experienced and naive patients (P<.0001), but the difference between the groups persisted into the third year of follow-up (P=.0007). Even patients who had experienced <2 months of nucleoside therapy before beginning HAART had an increased risk of virus rebound (RH, 1.95; P=.009). It appears that only a small period of pre-HAART nucleoside therapy is sufficient to confer a disadvantage, in terms of risk of virus rebound, that persists for several years.

Adult↗
PubMed2002

The incidence of lymphoma in the UK haemophilia population between 1978 and 1999.

OBJECTIVE: To determine the incidence of non-Hodgkin's lymphoma (NHL) and Hodgkin's disease (HD) in the UK haemophilia population during the 22 year period 1978-1999. DESIGN AND METHODS: An analysis of patient data included on the UK Haemophilia Centre Doctors' Organisation lymphoma register. The number of cases of NHL and HD occurring in HIV-positive and negative patients in each 3-year period were compared with the expected incidence in the general male population. RESULTS: Eighty-nine cases of lymphoma were identified. Seventy-two cases (81%) occurred in HIV-positive patients (67 NHL, five HD), and 17 cases (19%) in HIV-negative patients (nine NHL, eight HD). The incidence of NHL in the HIV-positive cohort was significantly increased, with a ratio of observed to expected cases of 83.92 (P < 0.001) in the period 1985-1996. The ratio reduced to 42.15 during the period 1997-1999, presumably as a consequence of the introduction of highly active antiretroviral therapy (HAART). There was a significant excess of HD in HIV-positive patients, with an observed to expected ratio of 10.50 between 1985 and 1999 (based on five cases, P < 0.001). During the whole observation period, there was a significant excess of HD in HIV-negative patients, with an observed to expected ratio of 2.66 (based on eight cases, P < 0.05). CONCLUSION: The incidence of lymphoma is significantly higher in HIV-positive UK haemophilia patients compared with HIV-negative individuals. Since the introduction of HAART, the incidence of lymphoma has tended to fall in the HIV-positive group.

HIV Infections↗
PubMed2002

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.

Adolescent↗
PubMed2002

Association of virus load, CD4 cell count, and treatment with clinical progression in human immunodeficiency virus-infected patients with very low CD4 cell counts.

This study prospectively assessed the impact of treatment modality, virus load, and CD4 cell count of <50 cells/mm(3) on human immunodeficiency virus disease progression. The incidence rate of new AIDS disease or death was 54.8 (95% confidence interval, 48.7-59.9) per 100 person-years of follow-up. Independent predictors related to progression were latest CD4 cell count (relative risk [RR], 0.84/10 mm(3) higher; P<.0001), latest hemoglobin level (RR, 0.79/g/L higher; P<.0001), Pneumocystis carinii pneumonia prophylaxis (RR, 0.49; P<.0001), latest body mass index (RR, 0.93/kg/m(2) higher; P=.002), latest virus load (RR, 1.11/log(10) higher; P=.03), and intensity of treatment (RR, 1.82, P=.004; RR 2.27, P<.0001; RR 2.46, P=.0001; RR 2.33 P<.0006; 5.10, P<.0001, respectively, for 4, 3, 2, 1, or no drugs vs. >or=5 drugs). Although reverse causality cannot be excluded, more intense antiviral treatment appears to decrease the risk of progression in immunocompromised patients.

Adult↗
PubMed2002

Virologic and immunologic response to regimens containing nevirapine or efavirenz in combination with 2 nucleoside analogues in the Italian Cohort Naive Antiretrovirals (I.Co.N.A.) study.

This nonrandomized study compared the virologic and immunologic responses to potent regimens containing either efavirenz or nevirapine after considering potential systematic differences between patients receiving these drugs. Virologic failure was defined as the first of 2 consecutive measurements of virus load >500 human immunodeficiency virus RNA copies/mL. Of the 694 patients included in the analysis, 460 (66.3%) started nevirapine and 234 (33.7%) started efavirenz. The adjusted relative hazard of virologic failure for patients who started nevirapine, compared with those who started efavirenz, was 2.08 (95% confidence interval, 1.37-3.15; P=.0006). In addition, patients receiving efavirenz tended to recover 5 CD4 cells/microL more per quarter (P=.05). Although comparisons of drug efficacy in nonrandomized studies should be viewed with caution, no results from randomized controlled comparisons of these drugs are thought to be available. The findings of this study are in agreement with those of other observational studies.

Acquired Immunodeficiency Syndrome↗
PubMed2002

Raised viral load in patients with viral suppression on highly active antiretroviral therapy: transient increase or treatment failure?

OBJECTIVE: To assess the occurrence of viral load greater than 50 copies/ml in patients on highly active antiretroviral therapy (HAART) having achieved less than 50 copies/ml and the chance of whether a viral load greater than 50 copies/ml would lead to a sustained and increasing viral load. DESIGN: A cohort of 553 patients on HAART with viral loads of less than 50 copies/ml were followed. RESULTS: Over a median of 56 weeks 35% of patients experienced a transient increase and 8% virological failure (two consecutive viral loads of > 400 copies/ml). Transient increases and virological failure were more common in those with greater drug experience, and those with initial raised viral load values of more than 400 copies/ml were more likely to have a sustained increase and become virological failures. CONCLUSION: Transient increases in viral load are common, mainly in the 50-400 copies/ml range, and the majority of subsequent viral load estimations show a return to less than 50 copies/ml. A single raised viral load should lead to adherence support and intensified monitoring. Subsequent treatment decisions can then be based on evidence of true virological rebound and failure.

Antiretroviral Therapy, Highly Active↗
PubMed2002

Gender and clinical outcomes after starting highly active antiretroviral treatment: a cohort study.

OBJECTIVE: To examine gender differences in clinical response to highly active antiretroviral treatment (HAART). METHODS: A cohort of HIV-positive individuals was examined. Outcomes assessed were hospital admission and disease progression (either a new AIDS diagnosis or death) after starting HAART. Hazard ratios (HRs) derived using Cox regression methods compared female-to-male rates, adjusting for other factors independently associated with outcome. RESULTS: Four hundred ninety-seven men and 146 women were followed up over a median of 13 months after starting HAART. Eighty-one percent of men were white, and 75% were homosexual. Fifty-eight percent of women were black African, and 86% were in the heterosexual risk category. The baseline CD4 count was higher in men than in women (191 vs. 145 x 10; p < .01), but viral loads were similar (5.2 vs. 5.1 log copies/ml, respectively; p = .13). Fifty-six percent of men and women were treatment naïve. Eighteen percent of men and women were admitted during follow-up, with 17% of male admissions and 12% of female admissions being the result of an AIDS-defining illness. The HR for admission was 0.76 (95% confidence interval [CI]: 0.46-1.27; p = .30) for women relative to men. Eleven percent of the men and 8% of the women experienced progression. Eighty-eight percent of progressions were the result of a new AIDS diagnosis (46 in men, 11 in women), and 8 men died. The HR for progression was 0.70 (CI: 0.36-1.33; p = .28). CONCLUSIONS: Our results suggest a possible benefit in women compared with men in the rate of outcomes after HAART. Further analysis with longer follow-up or greater numbers would enable a more powerful analysis to be performed.

Antiretroviral Therapy, Highly Active↗
PubMed2002

Virological suppression at 6 months is related to choice of initial regimen in antiretroviral-naive patients: a cohort study.

BACKGROUND: Guidelines recommend both protease inhibitor (PI)- and non-nucleoside reverse transcriptase inhibitor (NNRTI)-containing regimens for initial therapy in HIV-positive individuals whilst clinical trial data comparing treatment options remain limited. OBJECTIVE: To assess whether drug selection (PI versus NNRTI) in antiretroviral-naive patients is related to virological response at 6 months within a clinical cohort. DESIGN: Databases from two large clinics were used to identify all treatment-naive patients initiating highly active antiretroviral therapy (PI/ two PI or NNRTI). Statistical models determined the likelihood of suppressing HIV viral load < 500 copies/ml, the risk of treatment failure by 6 months, and factors associated with treatment success. RESULTS: Of 1109 potentially eligible patients 888 met study criteria and were included; 484 were prescribed a PI (40% indinavir, 41% nelfinavir) and 404 were prescribed NNRTI (40% efavirenz, 60% nevirapine). Three treatment arms were compared: efavirenz versus nevirapine versus PI. After stratification by year and centre and adjustment for baseline variables, only treatment group and baseline viral load remained significantly associated with virological suppression at 6 months. Patients on efavirenz were significantly more likely to achieve an undetectable viral load than those on PI or nevirapine. The relative hazard for nevirapine was 0.77 (95% confidence interval, 0.61-0.96, P = 0.02) and that for PI was 0.74 (95% confidence interval, 0.58-0.94, P = 0.01). Efavirenz also performed better in the analysis of treatment failure at 6 months. CONCLUSION: Although observational cohort data may be susceptible to significant bias, this study suggests a better initial virological response for efavirenz compared to either nevirapine or the PI. Clinical trial data is required to confirm these findings.

Adult↗
PubMed2002

A clinically prognostic scoring system for patients receiving highly active antiretroviral therapy: results from the EuroSIDA study.

The risk of clinical progression for human immunodeficiency virus (HIV)-infected persons receiving treatment with highly active antiretroviral therapy (HAART) is poorly defined. From an inception cohort of 8457 HIV-infected persons, 2027 patients who started HAART during prospective follow-up were examined. Results were validated in another 2 groups of patients (n=1946 and n=1442). In total, 200 patients (9.9%) experienced clinical progression during 5177 person-years (incidence, 3.9/100 years). The most recently measured CD4 cell count, virus load, and hemoglobin level all were independently related to the risk of clinical progression, as was a diagnosis of severe AIDS before the start of HAART. On the basis of these findings, a scoring system was derived (range, 0-17). A single unit increase in the score was associated with a 38% increased risk of clinical progression (relative hazard, 1.38; 95% confidence interval, 1.33-1.43; P<.0001). The scoring system was validated with remarkably good agreement in the 2 other cohorts. This system can be used in patient and resource management.

Adult↗
PubMed2002

Brief report: two-year outcome of a multidrug regimen in patients who did not respond to a protease inhibitor regimen.

In most studies, people who have not responded virologically to a protease inhibitor (PI)-containing regimen have tended to experience poor virologic responses to subsequent regimens. We describe the 2-year viral load, CD4 count, and clinical outcome of a multidrug regimen used in 60 people who had not responded virologically to a PI-containing regimen. At baseline, median CD4 count was 126/mm(3) (nadir 30/mm(3) ) and median viral load was 320,000 copies/mL. A median of five antiretroviral drugs had previously been used, of which a median of two were PIs. Of these patients, 16% had previously used another nonnucleoside reverse transcriptase inhibitor besides efavirenz. The multidrug regimen (median 5 drugs) started most commonly included efavirenz (100%), at least one PI (92%, usually indinavir/ritonavir), didanosine (78%), and hydroxyurea (74%). At year 2, 5 patients had died and 5 had no measure available. Nine patients developed a new AIDS event and 10 patients were known to have stopped all antiretroviral therapy. Thirty-one patients (52% of the whole group, 72% of those remaining on therapy with viral load value available) had viral load <50 copies/mL. Thus, a substantial proportion of patients who had failed to respond virologically to PI-containing regimens can achieve profound and sustained virologic suppression with a multidrug regimen.

Acquired Immunodeficiency Syndrome↗