Prevalence of tuberculosis among perinatally exposed to HIV and HIV-infected children and predictors of its development

Purpose of the study. To establish risk factors for tuberculosis (TB) in children perinatally exposed to HIV and HIV-infected for the development of corrective measures. Materials and methods. Outpatient records (form No. 025/y) of 216 children perinatally exposed to HIV and 121 children with HIV infection and their parents (281 individuals) were analyzed. The control group consisted of 100 healthy children. Epidemiological (descriptive, evaluative and analytical) and statistical research methods were used in the study. Results. The likelihood of contact with a patient with an active form of TB was significantly higher in perinatally exposed to HIV and HIV-infected children compared to children in the control group ( p < 0.001). The risk of TB in HIV-exposed children was 5.3 times higher in foci where both parents were HIV-infected than in foci formed by discordant couples (RR = 5.3; 95% CI 1.7–21.7). Children in study groups who were not vaccinated with BCG had the highest risk of TB compared to children in the control group (RR = 1.9; 95% CI 1.6–2.2). Risk factors for TB in children perinatally exposed to HIV are untimely vaccination against TB or its absence and living in the foci where both parents are HIV-infected. The predictors of the development of TB in HIV-infected children are household contacts with TB patient , late diagnosis of HIV infection, and late prescription of highly active antiretroviral therapy after the formation of severe immunosuppression.

the increasing number of patients with late-stage HIV infection. In 2008-2017, in Russia, the incidence of concomitant infections (HIV and TB) increased by 3.5% (5.2 0 /0000 in 2008 against 7.1 0 /0000 in 2017) [4]. Higher mortality rates were observed in TB and HIV coinfected patients; in 2018, the mortality reached 23% among the newly diagnosed HIV and tuberculosis patients [5].
With the increasing number of coinfection (HIV + TB) cases among adults, the probability of children being infected increases from 60 to 85% [6,7]. Multiple studies show that the increased TB incidence among children was caused by children's living in households with HIV-infected adults [8].
TB in HIV-infected children has its specific characteristics: High frequency of disseminated forms (71%) and high mortality, especially among children under 2 years of age due to functional immaturity of their immune system [9,10].
HIV-infected children with more advanced HIV disease are at higher risk of combination of extrapulmonary and pulmonary TB disease, including its dissemination [11]. The most severe clinical forms of TB, according to most of the authors, develop in patients with the advanced stage of HIV infection in the absence of highly active antiretroviral therapy (HAART) [12].
The group most vulnerable to TB is represented by children under 3 years of age, especially in TB-affected

Introduction
According to the World Health Organization (WHO), people infected with HIV account for 9% of the number of tuberculosis (TB) 1 cases; people living with HIV are 18 (15)(16)(17)(18)(19)(20)(21) times more likely 2 and children are 42 times more likely to develop active TB disease than people without HIV [1].
There are scarce data on the TB incidence among HIV-infected children, and the available information is difficult to interpret due to the problems with diagnosis, under-ascertainment, and selection of study populations. WHO estimates that the HIV prevalence among children with TB ranges from 10 to 60%, and varies depending on the background rates of HIV infection [2].
In 2018, the estimates made by O.B. Nechaeva for TB incidence among HIV-infected population resident in Russia were compared with estimates of TB incidence among the non-infected population. It was found that TB infection was 58.6 times more common among HIV-positive people than among HIV-negative people (1764.3 per 100 thousand HIV-infected people against 30.1 per 100 thousand population without HIV) [3].
The situation was aggravated by the increasing percentage of people with HIV/TB coinfection along with 1  ground and on the course of the disease [14]. Among the most adverse factors, most of the authors point out alcohol dependence and drug addiction of adult members of the family (at least, of the mother), low incomes and unfavorable ethical and emotional family environments [15][16][17][18]. At present, the frequency of occurrence and risk factors for TB infection among perinatally HIV-exposed and HIV-infected children have been largely understudied.
The aim of the study is to identify risk factors for TB infection among perinatally HIV-exposed and HIV-infected children for the further development of corrective actions.

Materials and methods
The prospective cohort study was aimed to identify risk factors for TB infection by analyzing medical records (Form 025u) of 216 children having a perinatal exposure to HIV and absent virus transmission as well as medical records of 121 children with HIV infection, including 61 children with coinfection (HIV + TB). All of them underwent regular medical check-ups at the clinical and diagnostic department of the Regional Center for AIDS Prevention and Control.
The inclusion criteria for the study enrollees were as follows: regular medical checkups, Ekaterinburg residency and perinatal infection. The exclusion criteria included residency outside Ekaterinburg and other routes of infection.
A total of 281 medical charts of the parents were analyzed to estimate the degree of exposure in the TB-affected households where the children lived.
The control group was composed of 100 children born to HIV and TB-negative mothers at maternity hospitals in Ekaterinburg.
CD4-lymphocyte counts were measured at the time of clinical diagnosis to assess the immune status of the HIV-infected children. The assessment of immune disorders in the respective age groups was performed in compliance with Clinical Guidelines No. 459, HIV Infection in Children, which were adopted by the Ministry of Health of the Russian Federation in 2017 (for children under 5 years of age -by CD4 percentage; for children older than 5 years -by absolute CD4-lymphocyte count).
The study included epidemiological (descriptive, evaluative, and analytical) and statistical research methods. The statistical analysis of the obtained data was performed by using Microsoft Excel 2016 and Statistics 23.0 software programs (IBM SPSS Statistics). Computations included the arithmetic mean (M), stan-dard error (m), mean squared deviation, and the median (Me). The study validity was verified with the help of Pearson's chi-squared text (χ 2 ), Student's t-test (t), and the Fisher angular distribution (φ). The risk factors for TB development in HIV-infected children were assessed with the odds ratio within the 95% CI. For perinatally HIV-exposed children, we used the univariate analysis to assess the relative risk (RR) of tuberculosis development. The logistic regression analysis with a stepwise variable selection option was performed to identify independent risk factors. The statistical significance was set at p < 0.05.
The study was approved by the local Ethics Committee of the Ural State Medical University (Approval No. 9 dated 18.11.2018). The parents signed their informed consent to have their and their children's personal data processed.

Results
In the group of perinatally HIV-exposed children, 73.8% of children were born to two-parent families, in more than fifty percent of which both parents were HIV-positive ( Table 1).
In 17 TB-affected households with parents having TB, 22 children were in household contact. More than half of the parents with TB disease belonged to TB care Group 1. The TB prevalence among the fathers was 1.9 times as high as among the mothers (8.5 ± 2.6% compared to 4.4 ± 1.6%; p > 0.05).
In addition to TB, some of the parents were bloodborne hepatitis virus carriers and continued using injection drugs. The hepatitis attack rate among mothers was 30.0 ± 3.6% and was 2.2 times higher than among fathers -13.6 ± 3.2% (t = 3.4; p < 0.05). Mothers used injection drugs slightly more often than fathers (21.3 ± 3.2% compared to 17.8 ± 3.5%; p > 0.05).
The occurrence frequency for TB-affected households among concordant and discordant couples was highly different, amounting to 19.5% compared to 4.9%, respectively (φ = 2.4, p < 0.01). In households where both parents were HIV infected, active TB was diagnosed in 60% of parents, while in household with one HIV-infected parent, it was diagnosed in 50%.
When assessing the risk of TB development in households of discordant and concordant couples, it was found that in households where both parents were HIV-infected, the children's possibility of TB disease following infection was 5.3 times higher than in households with HIV-discordant couples (RR = 5.3; 95% CI 1.7-21.7; Table 2).
The household TB contacts differed in BCG vaccination coverage and timing patterns. In the households with discordant couples, all children were vaccinated against TB, though not always on schedule. In the households with concordant couples, 90% of children were vaccinated; however, only a third of them were vaccinated at maternity hospitals, while the other two DOI: https://doi.org/10.36233/0372-9311-73 ORIGINAL RESEARCHES  thirds received vaccination in the first year of life and after 1 year of age. Some of the children (10%) were not vaccinated due to their parents' refusal of vaccines, and 1 child was diagnosed with intrathoracic lymph node tuberculosis, thus being exempted from BCG vaccination.
Considering that one of the risk factors for TB disease in children is their delayed vaccination, we analyzed time frames of BCG vaccination received by the children from the study groups, including their immune status ( Table 3).
It was found that the perinatally HIV-exposed children, who were not vaccinated against TB at the maternity hospital, accounted for 65.7%, while the HIV-infected children accounted for 38.8%, thus 3.7 and 2.2 times exceeding the unvaccinated proportion in the control group (18%). Therefore, unvaccinated children from the study groups had a higher risk of infection as compared with the children from the control group. The HIV-infected children were 4.7 times as likely to be household contacts of TB cases as compared to HIV-exposed children ( Table 4). More than half of the parents of children from study groups were bloodborne hepatitis viruses carriers, including the hepatitis C virus (90%; p < 0.001). Unlike parents of the children from the control group, they continued using injection drugs, though no significant difference in the drug-use frequency was found in the study groups.
To estimate the significance of individual risk factors for TB disease in children, we performed a comparative analysis of 9 variables in two specially formed groups: The first group was composed of 61 children with coinfection (HIV + TB); the second group inclu ded 60 HIV-infected children without TB ( Table 5).
The mean age of detection of HIV infection in coinfected children was 25.8 ± 3.4 months (95% CI 19.4-33.5) as compared to monoinfected children whose age of detection of HIV infection was 18.5 ± 4.1 months (95% CI 11.2-27.5), which fits well into the HIV diagnosis time frames 3 . Among the children with coinfection (HIV + TB), the HAART initiation time from the HIV infection diagnosis exceeded 8.6 times the initiation time for monoinfected children (31.1 ± 5.3 months compared to 3.6 ± 1.5 months).
The analysis showed that the most significant factors for development of TB among HIV-infected children included household TB contacts, late diagnosis of HIV infection and initiation of HAART beyond 6 months of the diagnosis when children already developed severe immunosuppression.
The obtained results were used to build a logistic model for estimation of the probability of TB development in HIV-infected children ( Table 6).
The model building made it possible to identify 5 independent factors having an impact on TB incidence among HIV-infected children: • contact with a TB case (p = 0.0001); • late diagnosis of HIV infection (p = 0.04); • severe immunosuppression at the time of diagnosis (p = 0.004); • initiation of HAART beyond 6 months of the diagnosis (p = 0.001); • deviant behavior of parents (p = 0.01). Absent vaccination against TB in HIV-infected children was not considered a risk factor for the disease; however, the assessment of the vaccination effica cy among coinfected children in different age groups showed that in the group of children from 3 to 6 years of age, the TB incidence among the unvaccinated children was 1.7 times higher than the TB incidence among the vaccinated children (63.2% compared to 36.8%) ( Table 7). 3     84 cases of TB disease were recorded among the HIV-infected children. Based on the report "Data on People with Tuberculosis Disease" (Form No. 33), in 2009-2018, the incidence among the children having household contacts with active TB cases showed an upward trend with average annual growth rate of 6% and was 1.9 times higher than the incidence among adults ha ving the similar exposure (Figure).

Discussion
The Sverdlovsk Region ranks among the regions with the highest prevalence of HIV + TB coinfection [4]. Based on the data from report form No. 61 "Information about HIV-Infected Population", the prevalence of coinfection was 22.1 per 100,000 population in the region in 2018 and was 2.7 times higher than the aver age level in the country (8.5 0 / 0000 ). In 2004-2018,   The probability of TB infection in children from HIV-affected households is high due to social and epidemiological factors.
The study of TB risk in children (meta-analysis), which was conducted in the United States, demonstrated that HIV-infected children were more vulnerable to TB disease following infection (OR 2.80; 95% CI 1.62-4.85) [12]. Studies conducted on the African continent confirmed that the number of TB and HIV pediatric cases in sub-Saharan African countries exceeded the numbers recorded in other regions of the world; as a result, in 2019, WHO declared the region the world's most TB/HIV burdened region (86% of TB patients had HIV antibodies) 4 .
In their studies, Yakovlev et al. demonstrated that the risk of TB disease in perinatally HIV-infected children is 42 times as high as in children born to HIV-negative mothers [19].
The data from foreign researchers show that from 30 to 50% of HIV-infected children contracted TB infection through household contacts with adults (parents, grandparents) having TB infection [8]. Eremenko et al. found that the main risk factor for TB development in children was their contact with a TB case, and the HIV-infected children had the exposure rate twice as high as compared to HIV-negative children -80.76 and 42.0%, respectively [20].
In our study, the analysis of the risk factors of TB infection among perinatally HIV-exposed and HIV infected children also showed that the rate of their TB exposure was higher than among the children of the con-trol group, thus being consistent with the data obtained by other researchers [8,20].
The parents of children from the study groups, unlike the parents of children from the control group, had a low level of social responsibility, as they continued using injection drugs and were carriers of bloodborne hepatitis viruses, contributing to unfavorable environments and TB spread. Our results support the studies conducted in St. Petersburg, where parental substance abuse was recorded for 85% of TB/HIV-coinfected children compared to 22% of children in the HIV-uninfected group (p = 0.02) [21].
In our study, the HIV-infected children had household TB contact 4.7 times more frequently than the perinatally HIV-exposed children (p < 0.001). The risk factors of TB development in perinatally exposed children included living in a TB-affected household where both parents were HIV-infected (RR 5.3; 95% CI 1.7-21.7) and absence of BCG vaccination. It was found that the risk of TB infection was 1.7 and 1.9 times higher in the study groups for children who had not been vaccinated against TB at maternity hospitals as compared to the children from the control group.
It has been proved that in HIV-infected children, the resistance to TB infection depended on the initial level of immunosuppression, on progression of HIV infection and on its stage [22]. In her study of clinical progression of TB in HIV-infected children in the Sverdlovsk Region in 2004-2012, N.V. Eismont showed that the probability of TB development among HIV-negative children was lower than among children with late stages of HIV infection (p < 0.001) [9].
In our study, one of the independent factors of TB development in HIV-infected children was a late diagnosis of HIV infection and late initiation of HAART when severe immunosuppression was already developed. The comparative analysis of immune disorders diagnosed in HIV-infected children demonstrated that the percentage of children with profound immune deficiency in the coinfected group was 2.2 times higher and amounted to 54.1% compared to 25.0% in the monoinfected group, thus supporting the findings of other researchers. In their meta-analysis that included data of 64 cohorts of TB and HIV-infected children, Dodd et al. concluded that TB incidence was 5 (95% CI 4.0-6.0) times higher in children with severe immunosuppression compared with non-significant one [12].
The study conducted in the Primorsky Krai found that among perinatally HIV-infected children having TB, most of the children had stage 4A (61.2%); 23.5% of children had stage 4B, while the stage 4 patients accounted for only 6% in the cohort of children without TB [19].
Our study has found that earlier initiation of HAART after TB diagnosis reduces the risk of TB infection 2.1 times, which is confirmed by other studies. It was proved that among HIV-infected children receiving HAART, the incidence of TB was lower (RR = 0.30; 95% CI 0.21-0.39) than among children not receiving HAART [12]. After initiation of HAART, the TB incidence decreased within 12 months to RR 0.10 (95% CI 0.04-0.25) [12].

Conclusion
Risk factors for TB development among perinatally HIV-exposed children are household contacts with active TB, parental HIV concordance and delayed or absent vaccination against TB.
Predictors of TB disease among HIV-infected children can include a household TB contact, late diagnosis of HIV infection, severe immunosuppression, initiation of HAART later than 6 months after the confirmation of diagnosis, and deviant behavior of parents.
The most essential corrective measures are early diagnosis of HIV infection and timely initiation of HAART as well as isolation from the source of infection and timely vaccination against TB in accordance with the National Immunization Schedule of the Russian Federation.