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R Bellocco

Publications and source records attributed to R Bellocco.

15 recordsLinked to original sources
PubMed2000

Joint analysis of HIV and AIDS surveillance data in back-calculation.

AIDS surveillance data are the main source of information to perform back-calculation of HIV incidence. We propose a method to incorporate additional information gained by linkage with an HIV surveillance system, containing data on the time of first positive HIV test. In this paper we generalize an earlier method that was developed to use HIV testing data available only for AIDS cases. The new method also makes use of cases with an HIV positive test who have not yet developed AIDS, typically a substantial proportion of the HIV-infected population. Furthermore, we use a more realistic model for the HIV testing rate, incorporating dependence on both time since infection and calendar time. The method makes use of an EM algorithm with generalized additive model smoothing, and is applied to data from Veneto, a region of northern Italy. Our results show that HIV incidence in Veneto peaked in the late 1980s, and decreased thereafter. Importantly, the HIV incidence estimates based on joint analysis of HIV and AIDS surveillance data are more efficient than estimates based on AIDS surveillance data alone. Our estimates also show a decreasing trend in the HIV testing rate over time, which leads to the conclusion that the interval between HIV infection and first positive test has lengthened over time. Furthermore, it is found that for infected individuals, the probability of seeking on HIV test is highest soon after infection.

AIDS Serodiagnosis↗
PubMed1998

Poisson regression.

Explore the source record for details and available documents.

Epidemiologic Methods↗
PubMed1994

Median time from seroconversion to AIDS in Italian HIV-positive haemophiliacs: different parametric estimates.

The purpose of this study was to estimate the median incubation time between human immunodeficiency virus (HIV) infection and onset of acquired immunodeficiency syndrome (AIDS), using three parametric models and six estimates of seroconversion time. Study subjects were 732 HIV-positive haemophiliacs enrolled in the Italian Registry of patients with congenital coagulation disorders. Seroconversion time was estimated for each subject according to six different criteria, based on three distributions of seroconversion (uniform, uniform on three sub-intervals and truncated Weibull) and two indices synthesizing each distribution (median and median of three random values). The estimated seroconversion times were subsequently used as starting points in the analysis of incubation. This was performed applying Kaplan-Meier non-parametric survival analysis, and fitting to incubation data three probability density functions, representing three different situations with respect to the hazard of developing AIDS following seroconversion (namely Weibull (WE), generalized exponential (GE) and log-logistic (LL)). The cumulative incidence over an 8-year period ranged from 14.9 to 17.8 per cent when applying the Kaplan-Meier method, from 14.1 to 17.2 per cent when using the WE function, from 14.5 to 17.3 per cent when using the GE function and from 14.4 to 17.3 per cent when using the LL function, depending on the estimate of seroconversion time used. Similarly, the median incubation times ranged from 12.6 to 15.0 years with the WE function, from 14.0 to 16.5 years with the GE function, and from 13.4 to 16.1 years with the LL function. The presence of a bound on the increase of the hazard function seems to affect the incubation more strongly than the eventual decrease following the attainment of the maximum risk. This may be due to the decrease in the hazard beginning when most of the seropositive subjects have already developed AIDS.

Acquired Immunodeficiency Syndrome↗
PubMed1994

Clinical and mycological evaluation of fluconazole in the secondary prophylaxis of esophageal candidiasis in AIDS patients. An open, multicenter study.

A prospective, multicenter, open study of fluconazole prophylaxis was performed in AIDS patients to evaluate the efficacy and toxicity of the drug in preventing relapses of esophageal candidiasis. To this aim, 99 AIDS patients who presented a first episode of clinically and microbiologically confirmed esophageal candidiasis were enrolled in eleven clinical centers scattered throughout the Italian territory. After resolution of this initial esophagitis, all subjects were given fluconazole, 100 mg/die, and followed up for a 6 month period. Only 7 out of the 99 patients enrolled had a relapse of Candida esophagitis, during a mean follow-up period of 138.5 days. All relapsing patients had CD4+ cell number < 100/microliters at baseline. Mild side effects were reported in only eight patients. However, 14 of the 27 subjects from whom serial serum samples were available became (12) or remained (2) antigenemic during fluconazole prophylaxis, independently from relapse, suggesting the persistence of tissue-invasive, proliferating Candida cells. Overall, the data of this study suggest a beneficial effect of prophylactic maintenance therapy with fluconazole against Candida esophagitis, particularly in the population with > 100 CD4+/microliters. However, the data on Candida antigenemia in these patients invite the consideration of a relative inefficiency of the drug to eradicate the microrganism from the esophageal tissue.

AIDS-Related Opportunistic Infections↗
PubMed1994

Immune tolerance in hemophilia-principal results from the International Registry. Report of the factor VIII and IX Subcommittee.

40 Hemophilia Centers from the USA, Canada, Europe and Japan referred to the International Registry 204 patients with haemophilia A, treated by Immune Tolerance (IT) Protocols over the past two decades because of the presence of an inhibitor to FVIII. 82% of the patients were high responders, while IT was started with low levels of inhibitor (< 10 BU) in most (57.3%) of the cases. 69 patients (33.8%) were given the highest FVIII dosage (> or = 200 IU/kg/day), 71 (34.8%) intermediate dosages (50- < 200) and 64 (31.4%) the lowest dosages (< 50). Of 158 patients persevering with treatment long enough to judge the outcome thereof, 107 (67.7%) achieved tolerance, 12 (7.6%) had a partial response, while 39 (24.7%) did not respond. Multivariate logistic regression analysis showed that two variables were independently associated with the highest probability of success: the use of high dose protocols (> or = 100 IU/kg/day) (p < .0001) and the presence of low levels of inhibitor (< 10 BU) at enrollment (p = .004). The Kaplan-Meier inhibitor-free survival curve showed that tolerance is longlasting: only 1 out of 107 patients relapsed and the longest documented tolerant patient has been inhibitor-free for 16 years. 129 hemophiliacs were HIV Ab-negative at enrollment; of the 118 HIV-screened after the treatment, 18 (13.9%) were found to be HIV Ab-positive. IT can indeed modify the natural history of inhibitors to FVIII in hemophilia.

Adolescent↗
PubMed1993

Time from diagnosis of acquired immune deficiency syndrome (AIDS) to death among persons with blood-borne AIDS in Italy.

The objective of the study reported here was to analyze survival time and factors associated with more rapid death among persons with acquired immune deficiency syndrome (AIDS) in Italy who acquired human immunodeficiency virus (HIV) infection through the transfusion of blood (n = 115) or blood components (n = 111). Subjects included all persons with AIDS all reported to the Italian AIDS Registry. The Kaplan-Meier method was used to estimate both the median survival time from the date of AIDS diagnosis to the date of death and the median survival time stratified by age at diagnosis, time of diagnosis, and AIDS-indicator disease. The Cox proportional-hazard model was used to assess factors independently associated with death. The prognosis for persons with blood-borne AIDS in Italy remains poor: overall median survival time was estimated to be 9.2 months, with no significant differences between hemophiliacs and transfusion recipients (p = 0.91). The median survival time for subject > 60 years old was 6.0 months, which is a significantly shorter time than that for younger subjects (p < 0.001). Subjects diagnosed prior to 1988 had a median survival time of 8.2 months, which is a significantly shorter time than that for subjects diagnosed after 1987 (p < 0.03). Subjects neurologically affected by AIDS had a median survival time of 4.1 months, which is a significantly shorter time than that for subjects diagnosed with any other disease (p = 0.03). Such factors were independently associated with more rapid death.

Acquired Immunodeficiency Syndrome↗
PubMed1993

HTLV-II/HIV-1 coinfection and risk for progression to AIDS among intravenous drug users.

To determine whether coinfection with HTLV-II influences the course of HIV-1 infection, we evaluated the progression from asymptomatic HIV infection (CDC group II) to persistent generalized lymphadenopathy (CDC group III) to AIDS-related complex (CDC group IVA) to full-blown AIDS (CDC group IVC) to death from AIDS in two groups of HIV-seropositive intravenous drug users (IVDUs). The first group consisted of 123 patients infected with HIV-1 only, and the second comprised 22 patients with serological and molecular evidence of HTLV-II/HIV-1 coinfection. Results of the immunological and clinical follow-up indicated a greater likelihood of developing persistent generalized lymphadenopathy among individuals infected with HIV-1 alone than among those coinfected with HTLV-II. However, no statistical difference was detected between the two groups in the depletion of CD4+ cells, the temporal decrease of the CD4/CD8 ratio, or the progression to ARC or AIDS or to death from AIDS. These findings suggest that HTLV-II may have no effect on the clinical evolution of HIV infection in IVDUs, which may be explained by the lack of pathogenicity of the HTLV-II coinfecting strain(s) and/or other still unclear biological or immunological cofactors or mechanisms.

Acquired Immunodeficiency Syndrome↗
PubMedDate not supplied

The effect of covariates on the induction time of AIDS using improved imputation of exact seroconversion times.

This paper explores the effects of covariates such as age, gender, chronological time of seroconversion, and mode of virus transmission on the interval between HIV seroconversion and the development of AIDS. For many cohorts which are available to provide information about such effects, both the time of seroconversion and the time of onset of AIDS may be right- or interval-censored. To analyse these doubly-censored data, we propose a method in which we first estimate the marginal distribution of the chronological time of seroconversion and use this distribution to impute the seroconversion time for each subject. Subsequently, we estimate the distribution of induction times conditional on the seroconversion distribution. We apply this technique to a cohort of HIV seropositive subjects recruited from various outpatient facilities throughout Italy and show that age at seroconversion has the greatest effect on induction time.

Acquired Immunodeficiency Syndrome↗