The effect of the 1993 European revision of the AIDS case definition in Italy: implications for modelling the HIV epidemic

AIDS in Brazilian children: history, surveillance, antiretroviral therapy, and epidemiologic transition, 1984-2008

We present a systematic review of historical, political, and epidemiologic aspects of AIDS in Brazilian children. Over 25 years, Brazil has developed different strategies to control AIDS in children. Three revisions of criteria for defining AIDS cases in children and nine national guidelines on antiretroviral therapy administration for management of HIV infection were published. These guidelines represent important progress, including aspects of HIV/AIDS surveillance, antiretroviral treatment, opportunistic conditions, prophylaxis, and laboratory testing. Brazil has significantly expanded access to free therapy with different classes of antiretroviral drugs. Initially focusing on treatment for HIV and opportunistic conditions, the scope of treatment guidelines gradually expanded to comprehensive health care for children and adolescents. From 1996 to 2008, the number of AIDS cases and deaths in children has been reduced by 67% and 65%, respectively, as a result of different strategies to prevent mother-to-child transmission of HIV and highly active antiretroviral therapy administration to infected children. Improved morbidity, mortality, and survival of Brazilian children with AIDS demonstrate clear benefits of adopting a policy of free and universal access to antiretroviral drugs associated with comprehensive care. However, important issues remain to be resolved, mainly concerning social, operational, and regional inequalities in coverage and quality of care, and epidemiological surveillance in different regions of the country. This broad review shows that the overall situation of pediatric AIDS in Brazil represents an incomplete process of epidemiologic and demographic transition, with the coexistence of old and new clinical and epidemiologic challenges.

Increasing proportion of AIDS diagnoses among older adults in Italy

We evaluated the impact of AIDS among older persons in Italy and compared these cases with cases among younger persons. The data source was Italy's National AIDS Registry. We considered adults diagnosed with AIDS between 1982 and 2005. Older adults were defined as those aged 50 years or older at diagnosis. Of the total adult cases, 8.8% were among older adults. This proportion increased over time, from 4.9% in 1982-1990 to 15.9% in 2000-2005. Among older adults, the most represented exposure category (80.8%) was sexual intercourse (heterosexual and homosexual). At AIDS diagnosis, older adults, compared to younger adults, had a higher risk of developing AIDS dementia complex or wasting syndrome, and of presenting multiple AIDS-defining illnesses. A significantly lower proportion of older adults were undergoing antiretroviral therapy, compared to younger adults. Among older adults, 67.2% were late testers, compared to 32.8% of younger adults. Most of the older adults acquired the infection through sexual contact; approximately two thirds of them were diagnosed late (i.e., first HIV-positive test 6 months or less before AIDS diagnosis); and only one fourth were undergoing antiretroviral therapy at diagnosis. These observations stress the need to more seriously consider the possibility of HIV infection among older individuals and to collect more detailed information on their sexual behavior.

Increasing proportion of late testers among AIDS cases in Italy, 1996–2002

In recent years, the proportion of individuals who are unaware of being infected with HIV when diagnosed with AIDS (defined as 'late testers') has dramatically increased in several European countries, including Italy. We evaluated the extent and determinants of late testing and its impact in terms of AIDS-defining illnesses among AIDS cases reported to the Italian National AIDS Registry since 1996. Late testers were defined as those persons whose first positive HIV test result was within six months of the AIDS diagnosis. Late testers were more likely to be heterosexual contacts or MSWM, as opposed to IDUs. They were also more likely to come from low prevalence areas of Italy or from foreign countries. At AIDS diagnosis, late testers were less likely to be undergoing HAART or prophylaxis against PCP/toxoplasmosis, compared to non-late testers. The mean CD4 cell count at AIDS diagnosis was significantly lower among late testers. PCP, toxoplasmosis and Kaposi's sarcoma were more frequently diagnosed as an AIDS-defining illness in late testers, who also had a significantly higher risk of presenting with multiple concomitant AIDS-defining illnesses. In conclusion, late testing results in missed opportunities for preventing and treating HIV infection, leading to an increased risk of developing preventable opportunistic infections and death.

Back-calculation by birth cohort, incorporating age- specific disease progression, pre-AIDS mortality and change in European AIDS case definition. European Union Concerted Action on Multinational AIDS Scenarios

OBJECTIVES

To adapt and improve methodology for back-calculation of AIDS in Europe and to examine the feasibility of estimating past HIV incidence by birth cohort.

METHODS

Empirical Bayesian back-calculation (EBBC) used Markov disease progression models, modified to allow for three diseases added to the AIDS case definition in 1993 and for pre-AIDS mortality, and estimation by penalized maximum likelihood with a neighbour prior. EBBC by 5-year birth cohort assumed a minimum age at infection and age-dependent progression rates; three versions, with varying age effects, were investigated using AIDS cases diagnosed prior to the introduction of highly active antiretroviral therapies (HAART).

RESULTS

Compared with the no age-effect version, EBBC by birth cohort tended to produce flattened HIV incidence curves in country-exposure groups with < 1000 AIDS cases, reflecting effects of the neighbour prior when data become sparse. Otherwise, birth cohort analysis, with moderate effects of age on progression, gave initially increasing incidence curves and consistent patterns across countries, with the 1960-1964 cohort most affected. In the European Union, incidence is estimated to have peaked in 1983 among homosexual men and in 1988 among injecting drug users; 460000 persons were estimated to be living with HIV/AIDS at the end of 1995.

CONCLUSIONS

Our improved methodology deals effectively with the change in AIDS case definition and has allowed quantitative assessments of the HIV epidemic by birth cohort using all AIDS cases diagnosed before 1996, thus providing a sound basis for public health policy at a time when estimation of more recent prevalence is compromised by the effects of HAART.

The impact of the 1993 European revision of the AIDS case definition on back-calculation estimates: an application in Italy

OBJECTIVES

The revision of the case definition for AIDS within a given observation period causes discontinuity points on the epidemic curve to which back-calculation procedures can be sensitive. The aim of this work is to characterize the impact of the 1993 European revision of AIDS case definition and to evaluate the degree of distortion by which back-calculation estimates obtained on Italian data are affected.

METHODS

The back-calculation procedure used, is a generalization of standard methods for estimating and projecting the AIDS epidemic. Age at onset of HIV infection, incubation time distribution, susceptible population and competitive non-AIDS mortality rates for infected persons are included in the estimation process.

RESULTS

Back-calculation estimates resulted to be sensitive to the discontinuity point that the 1993 revision of AIDS case definition induced on the epidemic curve. The resulting effect is a tendency to overestimate HIV incidence in recent years by 20-40%. The maximum effect was found using data with end of AIDS cases at December 1993. The overestimation is a transient effect, that is, it is expected to almost disappear in 1995-1996.

CONCLUSIONS

The introduction of the 1993 European revision of AIDS case definition caused distortion of back-calculation estimates in Italy, leading to overestimate incidence and prevalence of HIV infection for recent years. It is believed that this effect has occurred in all countries that adopted the 1993 European revision of AIDS case definition, and its characterization is potentially useful for further changes of AIDS case definition in the future.