The risk of transmitting the human immunodeficiency virus when maintaining sexual relations may be 18, sometimes even during vaginal intercourse, as suggested by the results of a meta-analysis published in the early digital version of International Journal of Epidemiology.
On the other hand, in addition to this empirical work, the team of researchers from Imperial College and the Faculty of Hygiene and Tropical Medicine in London applied a mathematical model to calculate the impact that anti-HIV treatment had on the capacity of infection during relationships anales. It was determined that the transmission risk of a man with a viral load suppressed it could reduce up to 99,9%.
Anal sexual relations are the drivers of the HIV epidemic among gay and bisexual men. Asimism, a remarkable proportion of heterosexual persons practicing anal relationships, has yet to deploy condoms with less frequency than in the case of vaginal sex. You might be having an effect on heterosexual epidemics in sub-Saharan Africa and elsewhere.
Rebecca Baggaley and a team of collaborators will carry out a systematic review and a metanalysis (an analysis of all medical research that meets predetermined requirements) of the risk of HIV transmission during analogue relationships with protection. The same authors have made similar revisions to the transmission risk during vaginal and oral sexual relations.
Despite the importance of the subject, it is considered that only the 16 studios were relevant enough to be included in the review. If 12 tells of gay or bisexual men, other people gather data about heterosexual people who have anal sex with fruition. All the studies proceeded from Europe North America.
Around the team of researchers are looking for studies published in the past about 2008, where all the reports have been retrieved in the 1980 decade or the beginnings of 1990, which means that the hallmarks reflect on the impact of combined therapy on it. transmission. The authors could not include a studio with gay Australian men, published a few months ago [English en] [en español].
Calculation of transmission risk for each sexual act
Four studies offered calculations of the risk of transmission during a single act of receptive anal sex without protection. In addition to grouping data, the combined calculation is 1,4% (95% confidence interval [95% CI]: 0,3 - 3,2).
Of these tests have been performed with gay men and heterosexuals, and the results vary in the function of sexual orientation.
The calculation of the probability of infection during receptive anal relationships is identical to that published in the recent Australian study (1,43%; 95% CI: 0,48 - 2,85). This is despite the fact that the Australian data has been withdrawn after the widespread introduction of combined antiretroviral therapy.
The review does not identify any calculation of risk per act in the case of the insertive opinion. However, the recent Australian study did so: 0,62% in case of uncircumcised men and 0,11% in circumcised men.
Baggaley and his team of collaborators signal that their calculation of risk for receptive relationships is considerably higher than that obtained in previous revisions. In studies conducted in developed countries, the risk of transmission during vaginal intercourse was determined to be 0,08%, but in the case of receptive analogue relationships, 18 is estimated to be greater. When it comes to oral sex, there is an abanico range of figures, but no more than 0,04%.
Calculation of HIV transmission risk by partner
Sweet studies have provided data on the risk of transmission throughout the time in which a person with HIV maintains a relationship with another seronegative. The authors indicate that the majority of these tests are compiling sufficient information on factors such as the duration of the relationship, the frequency of sex with protection and the use of condoms so that the data will be completely significant.
In these studies only gay men participated.
In the case of relationships that practice both receptive and insertive protection relationships, the pooled transmission risk calculation is 39,9% (95% CI: 22,5 - 57,4).
While the reports that only had receptive relationships without protection, the joint calculation was the same, 40,4% (95% CI: 6,0 - 74,9).
However, it was less in the case of people who only maintained insertive relationships without protection: 21,7% (95% CI: 0,2 - 43,3). The team of researchers comments that the data supports the hypothesis that insertive relationships have a significantly lower risk of infection than receptive ones.
The individual studies on which these calculations are based will yield very different results, partly due to the different designs and analytical methods employed. As a result, the confidence intervals of the accumulated calculations are broad and the authors recommend that these data be interpreted with caution (a confidence interval of 95% offers a wide range of values: It is considered that the 'authentic' result is likely to be within the range, but may be of any value, including the highest and the lowest range).
In addition, the team of researchers claims that the risk calculations for each act do not seem to coincide with the calculations by partners. Their results would imply that relatively few cases of sex were produced without protection during the studied relationships.
The authors note that part of this discrepancy could reflect variations in the ability of infection and susceptibility to the same between people and also in the ability to transmit the virus over the course of an infection.
Impact of anti-HIV treatment on risk of transmission
As noted earlier, all of the studies from the previous era included antiretroviral therapy of high activity (TARGA). As a result, the team of researchers applied a mathematical model to calculate the reductions in the risk of transmission in personas with a suppressed viral load.
In order to do so, it explores the different types of calculations to establish the relationship between viral load and virus transmission capacity, from heterosexual studies in Uganda and Zambia.
The first calculation has been widely used by other researchers. Thus, each increase of 1log10 in viral load was considered to increase 2,45 times the transmission rate. It is also believed that this relationship is precisely fulfilled when the viral loads are between 400 and 10.000 copies / mL, Baggaley and his team consider that it overstates the transmission risk for both high and low loads.
The second calculation, but more complete, reflects that transmission is extremely rare when the viral loads are low and also that transmission rates are quite constant for higher viremia.
By supplementing the first method, the risk of HIV transmission in the case of receptive anal intercourse with protection from 0,06% (96% less than treatment). However, using the second method, the predicated transmission risk would be 0,0011%, but 99,9% is less than without treatment.
In extrapolating these data, the authors calculated the risk of HIV transmission in a relationship that would entail 1.000 cases of receptive analogue relationships without protection. Using the first method, the risk would be 45,6% and the second, 1,1%.
The authors point out that very different predictions have been obtained when they emerge from the different sets of assumptions regarding viral load. In the debate on the use of HIV treatment as a precaution, he commented: "Models cannot replace empirical problems."
In addition, in a commentary on the article, Andrew Grulich and Iryna Zablotska, from the University of New Wales of the South (Australia), indicate the absence of data on viral load and transmission during anal sex practice [all studies refer to heterosexual poblaciones]. He states that it is thought that the calculation of the risk of transmission by act is much higher during anal sex than during vaginal sex "is a solid argument not simply to extrapolate the data of heterosexual populations."
Baggaley and his team of Indian collaborators, whose halls suggest that the high risk of infection during analogue relations implies that, if treatment achieves a substantial reduction in infection capacity, “residual capacity would continue to suppose a great deal for partners. " Having said that, the prevention messages have to be of high relevance to anal sex practice and the importance of using condoms.
References: Baggaley RF, et al. HIV transmission risk through anal intercourse: systematic review, meta-analysis and implications for HIV prevention. Int J Epidemiol (online edition), doi: 10.1093 / ije / dyq057.
Grulich AE and Zablotska I. Commentary: Probability of HIV transmission through anal intercourse. Int J Epidemiol (online edition), doi: 10.1093 / ije / dyq101.