Time to develop tuberculosis and predictors of incidence among anti-retroviral therapy children on two selected hospitals at benishangule Gumuz region, North West Ethiopia: A retrospective cohort study

Background: Currently, tuberculosis (TB) incidence in peadtrics and children living with human immune-deciency virus (HIV) is an emerging global concern. Although, the incidence of TB among adult HIV patients is exhaustively studied; the incidence of TB among children on ART is overlooked. Knowledge of the time when TB develops among children on ART could be helpful to develop time relevant intervention strategies. Methods: This was a hospital based retrospective cohort study conducted among 429 children on ART from 2009-2018. Time to develop TB was dened as time from enrollment for ART care until development of TB among children on ART. Proportional hazard assumption was checked for each variable and no variable was found with Schoenfeld test <0.05. Variables with P-value <0.25 at bivariate Cox regression analysis were entered into multivariable Cox model. Multivariable Cox regression model with 95%CI and AHR was used to identify signicant predictor variables to develop TB at P< 0.05 Result: 421 children were followed for a total of 662.5 Person Years of observation (PYO). The maximum and minimum follow up time on ART was 0.37 and 4.49 years, respectively. The median age of the children on ART at enrollment was 9 years (SD=3.36). The Overall incidence density of tuberculosis in HIV infected children was 9.6/ 100 PYOs 95%CI (8.06-10.3). Tuberculosis occurrence among HIV infected children was signicantly associated within TB history of contact AHR=3.7, 95%CI (2.89-7.2), not started on cotrimoxazole(CPT) AHR=2.4: 95%CI (1.84-4.74), incomplete vaccination AHR=2.4, 95%CI (1.32-4.5), sever stunting AHR =2.99:95%CI (1.2-7.81), having hemoglobin (Hgb) ≤ 10 mg/dl AHR = 4.02, 95%CI (2.01-8.1) Conclusion: More than 80% of TB incidences occurred during two years of follow up after ART started. So


Introduction
The Intricate linkage of tuberculosis(TB) with HIV infection for the past three decades become major threat and hindrance for international public health effort to achieve Millennium development goal [1].
Globally, tremendous progress has been made over the past decades in diagnosing and treating of TB and achieved 2% per year new TB incidence reductions [2]. However, in 2017 6.4 million new incidence cases of TB were reported [3], among this 9% (0.3 million) were new incidence of TB-HIV co-infections and 50% of new infection including inborn seropositive children were located in resource limited settings [4]. It is mainly due to di culty in timely addressing prophylaxis and ART treatment gaps [5]. On the other hand, absence of sophisticated early HIV diagnosis technologies for inborn HIV infected children [6] increase early mortality by lethal opportunistic infections like TB [7,8]. It is one of the leading lethal opportunistic infection with 30-40% lifetime incidence risk for HIV infected children [9,10]. Global systemic review and meta-analysis on incidence of tuberculosis among PLWHIV in 2013 indicated , the incidence burden has variation in continental perspective [11], which is 31.25% in African countries, Page 3/20 25.06% in Latin America countries, 17.21% in Asian countries, 20.11% in European countries, and 14.84% in the USA [12]. Several studies in African countries have shown that the incidence of TB among HIV positive children ranges from 1-9.9 per 100PY [9][10][11]13] with different times of immunological and pathophysiological response for tuberculosis incidence [14,15], for instance in Uganda & Zimbabwe it was 1.9/100 P-Y [11] and in Tanzania it was 5.2/100 P-Y [10]. According to global TB report of 2018, Ethiopia found top 17 twine TB & HIV epidemic countries with 8.6-17/1000 new TB incident including seropositive children [3],With each year, 3900 HIV infected children develop morbidity by opportunistic infection especially by TB [15].
Childhood TB incidence rate varied in Ethiopia among different regions and health institutions [16]. For example, in Adama it was 6.03/100 P-Y [17], in Debre Markos 2.63/100P-Y [18], in Gondar 4.9/ 100 PY [19], in Northern Ethiopia 4.2 / 100 P-Y [20] and southern Ethiopia 2.6 /100 P-Y [21]. Another studies indicated predictor for TB incidence during ART follow up time were identi ed [17][18][19]22]. Mainly, bedridden functional status [20] WHO stage 3 & 4, not on ,anemia [20,23], rural residence [20], under nutrition [17] poor adherence [18]. Currently, tuberculosis incidence in peadtrics and children is an emerging and global concern due to its one of leading lethal opportunistic infection for children living with HIV [24]. Although, studies have been conducted on TB incidence among children on ART near the major cities [4] , the incidence of TB among children on ART at rural and nomadic community is incompletely described and overlooked [20,25]. In addition, information on the time when TB develops among children on ART is lacking too [11,19].

Study area, design and population
We conducted a retrospective cohort study on 429 children on ART on treatment and care from January 1 / 2009 to December 31 /2018 at Assosa & Pawe general hospitals in Benishangule Gumuz regions. Both hospitals are located in this regional state in North West Ethiopia. This region is one of the nine regions in Ethiopia. Assosa is the capital city of this region and it is located at a distance of 659 km in west of Addis Ababa and Pawe hospital is also located a distance from 565 km from Addis Ababa in North West direction. This region has currently 2 general and 3 primary hospitals with one regional laboratory. This two selected Hospitals are routinely diagnose and treat tuberculosis based on the clinical ndings, chest x-ray, AFB and XpertTB for suspected TB patients [26] . In both general hospitals there has been given ART care service 2007 pediatric HIV/AIDS guideline [27]. Following the time of enrollment to ART care continuum, all children have started ARV at both hospitals. Among these, 238 and 191 children were on follow up and care at Assosa general hospitals and Pawe general hospitals, respectively. From the registration logbook, eight children with incomplete outcome data were excluded from the study.
Sample size determination and sampling procedure Sample size for this study was calculated by using EPI INFO software using the following parameters. A) (α) of 5%, power 80%, Z = within 95% CI = 1.96 and AHR=2.39 [20] (P1) =6.6% and (P2) = 15.8% obtained 408 by adding 5% incomplete data nal sample size will be 421.Computer generated random number used for nal study subject of study subject from two hospitals. Totally there existed 723 children started HAART and registered on computer SMART DATA sets of ART registration o ce since

Operational de nitions
Case ascertainment: The outcome variables (TB) was diagnosed based on bacteriological, molecular, histopathology and clinical methods by using ( microscope, sputum culture, chest x-ray, and Xpert or combinations) during patient presentation for TB symptoms [28].
Pulmonary tuberculosis: Pulmonary tuberculosis (PTB) refers to a case of TB involving the lung parenchyma. Military tuberculosis is also classi ed as pulmonary TB because there are lesions in the lungs. Extra pulmonary tuberculosis (EPTB): refers to a case of TB involving organs other than the lungs [28].Event: New occurrence of tuberculosis during ART care follows up times with study in periods Censored: HIV positive children who did not developed TB during ART follow up.
TB history of contact: Children during ART follow up before TB incidence developed, having history of survives or contact at any time with who has active PTB patient.
Opportunistic infection: for HIV infected children during the following if any one of diseased developed registered on ART follow up form by their code (BP=Bacterial pneumonia ,UL= oral ulcer , Z=Herpes zoster, PCP = pneumocystis carnie pneumonia ,DC/DA -chronic / acute diarrhea, CT= central nervous toxoplasmosis CM streptococcal meningitis [29].
CD4 :was classi ed as below the threshold according to the following age-speci c thresholds: less than 15% for children aged 12-35 months, less than 10% for children aged 36-59 months or less than 100 cells/mm3 for children aged 5-15 years [20].
Seropositive: children<15 years were con rmed diagnosed of HIV /AIDS and under follow up.
Stunting, underweight, and wasting: The child being 2 standard deviations (SDs) below the normal for height for age, weight for age, or weight for height, according to the WHO 2006 curve. For children under or equal age 2, wasting was measured by weight for length Z-score; for children above age 2, wasting was de ned by Z-score. Z-score ≥ −2 was de ned as non-wasting; −3 ≤ Z-score ≤ −2 was de ned as moderate wasting; Z-score ≤ −3 was de ned as severe wasting. Stunting was measured by height/length for age Z-score. Z-score ≥ −2 was de ned as non-stunting; −3 ≤ Z-score ≤ −2 was de ned as moderate stunting; Z-score ≤ −3 was de ned as severe stunting [10,17,22].
Data collection tools, procedures, and quality control Four bachelor nurses and two supervisors were selected for data collection processes and all had took ART training. For quality of data collection process, one-day traing was given in two hospitals with two supervisors for data collectors. The principal investigator and two supervisor followed data. Data were collected using the data abstraction tool and medical history sheet prepared from Ethiopian Federal ministry of health HIV/AIDS follow up forms [15].

Data processing and analysis
Data entered into the computer using EPI-DATA version 3.

Discussion
To succeed WHO 2030 "End TB epidemic " strategies there must be collaborative working of TB program with HIV /AIDS patients to address su cient prophylaxis and ART gap [3]. Accordingly, the nding of this study indicated that the overall incidence of tuberculosis in HIV infected children was found 9.6/ 100 PYOs, 95%CI (8.06 -10.39). This in not comparable with study nding in southern Ethiopia 2.6/ 100 PYOs [21], Debre Markos 2.63 /100 PYOs [18] ,Northern Ethiopia 4.2/ 100 PYOs [20], Gonder 4.9/ 100 PYOs [19], Adama 6.03 /100 PYOs [17]. This might be due to higher burden of tuberculosis in resource limited settings for early diagnosis and intervention [26]. The study nding in South Africa indicate that the incidence of TB in HIV children is as higher as 21.1/ 100PYO [9]. This might be due to south Africa was classi ed as twine TB/HIV epidemic incidence site [31,32]. As time goes, incidence of TB in some settings lower been observed in recent times [20].According to the nding, this study HIV infected children not started cotrimoxazoles during their follow up time was independently associated with incidence of TB as compared with taking cotrimoxazole. This is in line with north Ethiopia [20] Adama referral hospitals [17].In fact it might be due to Cotrimoxazoles preventive therapy signi cantly reduces HIV related morbidity and mortality of lethal infections [3]. On the same way, this study nding also showed that HIV infected children having previous TB history of contact is independently associated with incidence of TB as compared with non-TB contact children. This is in line with the study nding in south Africa [9].In fact low educational status and lack of awareness about transmission of pulmonary TB might easily acquire the infection from chronic carrier of nearby patients [33].
The nding of this this study indicated among HIV infected children having incomplete vaccination has independently associated with the risks of developing TB as compared with children complete their vaccination. This is comparable with the study nding in Adama referral hospitals [17] and university of Gonder [19]. The nding of this research also indicated that HIV infected children having sever stunting was independently associated with incidence of TB as compared with HIV infected children has no stunting. This in line with the study nding in Adama [17],Tanzania [10], Uganda & Zimbabwe [11]. This might be due to HIV infection increases nutrient mal-absorption due to metabolic alterations that culminate in weight loss and stunting with time leads early exposed for opportunistic infections [29].
Similarly existence of rapid viral replication consumed body energy and create arena for incidence of TB [2,34].This study nding also showed that children having hemoglobin ≤10 mg/dl was independently associated with TB incidence as compared with HIV infected children having hemoglobin level >10mg/dl. This is in line with the study nding in Adama hospitals [17],university of Gonder referral hospitals [19] ,Northern Ethiopia [20], Dar es Salaam, Tanzania [10], in England and wales [23]. In fact this is due to hemoglobin levels had high predictive value for incident TB and death. TB incidence is directly associated with severe anemia [35]. Regardless of ART moderate or severe anemia during ART follow up can be independent predictor for TB [35,36] .

Limitation of the study
Retrospective nature of this study is one of the limitations of this study .due to this some of clinical important predictor variable which has independently associated with incidence of TB occurrence in other studies like educational status of children, economic status of family were not included in these study.

Conclusion
Incidence of TB was an important medical problem for children living with HIV ART treated in both Hospitals. This study nding concluded that baseline not ever taking cotrimoxazoles, ,having moderate stunting ,hemoglobin level lower than standard , incomplete vaccination ,having previous history of contact with TB has signi cantly and independently associated TB incidence. So intensi ed screening of cotrimoxazoles and malnutrition was highly recommended for intervention. Sciences department of public health in Debre Markos University. First formal letter was written from the university ethical board to Assosa and Pawe General Hospitals for data collection permission .After accepting and giving permission for collections of data by administrative staff in two general hospitals formal letter was written based on our request for work in ART peadtrics ward to conduct the study. Finally, individual consent from the study participates by their formal signature and a few of them by thumb nger to keep their con dentiality.

Consent for publications
No consent for publications Availability of supporting data All the datasets analyzed for this study is/are available in the corresponding author and can send based on reasonable request.

Competing interests
The authors declare that there are no competing interests. Funding: All funding of this original research process was covered by FK  The overall Kaplan-Meier TB free survival probability of HIV infected children from tuberculosis incidence since 2009-2018.