Effects of different parametric estimates of seroconversion time on analysis of progression to AIDS among Italian HIV-positive haemophiliacs

CD4 cell eligibility thresholds: an analysis of the time to antiretroviral treatment in HIV-1 seroconverters

BACKGROUND

WHO recommends initiating combination antiretroviral treatment at the minimal CD4 cell threshold of 350 cells/μl. In sub-Saharan Africa, the time for a recently infected patient to reach this threshold is unclear.

METHOD

We estimated the probability of reaching different CD4 cell thresholds over time in the ANRS 1220 cohort of HIV-1 seroconverters in Côte d'Ivoire. CD4 cell slopes were estimated using a mixed linear model. Probabilities of crossing the 350 and 500 cells/μl CD4 cell thresholds were estimated by the Kaplan-Meier method.

RESULTS

Between 1997 and 2009, 304 recent seroconverters have been enrolled in the Primo-CI cohort (62% men, median baseline age 29 years and median time since the estimated date of seroconversion 9 months). The probability of having a first CD4 cell count below 500 cells/μl was 0.57, 0.72, 0.79 and 0.84 at study entry, 2, 4 and 6 years, respectively. For a first CD4 cell count below 350 cells/μl, these figures were 0.29, 0.40, 0.55 and 0.67. The time for 75% of patients to reach the threshold was 3.0 years for 500 cells/μl and 7.0 years for 350 cells/μl.

Potential biases in estimates of hepatitis C RNA clearance in newly acquired hepatitis C infection among a cohort of injecting drug users

Estimates of hepatitis C virus (HCV) clearance following acute infection range from 14 to 46%. This wide range is likely to be due to the characteristics of the populations studied and analysis methods. This paper examines how differing definitions of clearance parameters affect estimates of viral clearance in a cohort of 85 injecting drug users with newly acquired HCV infection. Kaplan-Meier estimates of time to HCV clearance were determined using varying definitions of eligible cohort, viral clearance, date of infection and date of clearance. Based on which combinations of definitions were used, the number of subjects eligible for analysis ranged from 27 to 75, clearance rate ranged from 14 to 68% and time to achieving 25% clearance ranged from approximately 5 months to 14 months. Standardized definitions and methodologies are required to enable valid comparisons of rates of clearance across newly acquired HCV infection natural history studies.

Epidemiology of hemophilia and of HIV infection in Italy. GICC. Gruppo Italiano Coagulopatie Congenite

To evaluate the incidence and prevalence of hemophilia in Italy and the impact of HIV infection on the Italian hemophiliac population, data from a computerized national registry of patients from 95% of the hemophilia care centers in Italy were analyzed. A total of 4643 patients were included in the registry. The prevalence of hemophilia A was 8.2 per 100,000 males, with no significant regional differences; for hemophilia B the corresponding figure was 1.5 per 100,000. Temporal trends in hemophilia incidence suggest that the diagnosis of mild and moderate hemophilia has improved. The overall HIV prevalence was 26% and was significantly (p < 0.001) higher in patients with hemophilia B (47.1%) compared to those with hemophilia A (26.8%) or other diseases (16.5%). The highest rate of HIV seropositivity was among patients 20-29 years of age. The annual amount of clotting factor concentrates received was significantly (p < 0.001) higher in HIV seropositive patients than in those who were seronegative. Antibody testing was never performed on 10.1% of severely affected patients. The number of patients in the Italian registry was similar to the number that would have been expected based on prevalence estimates from other countries. In comparison with other countries, the prevalence of HIV infection recorded in Italy was lower in persons with hemophilia A, but higher in those with hemophilia B. Our study demonstrates the usefulness of a registry in delineating the epidemiology of hemophilia and in studying risk factors for HIV infection. It also underlines the need for continuing surveillance of this population.

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.