The incidence rate of this study was 6.3 per 100 children years of observation (CI = 5.21, 7.77). Up on running the final cox proportional hazard model statistically significant predictors for LTFU were being male, WHO stage III and IV, age between 1–5 years, stunted, poor and fair adherence to ART and regimen was not changed.
The overall incidence rate of this study is in line with the study conducted in Addis Ababa Ethiopia 6.26 per 100 children in years of observation(20). On the other side, the result of this study is lower than the studies conducted in Tanzania 18.2 per100 children in years of observation, Uganda 12.6 per100 children in years of observation and in South Africa 10.8 per 100 children in years of observation ( 24,33,34). This difference might be due to socio-cultural difference. In addition, in Tanzania the study includes both pre ART (before ART) initiation and post ART initiation children and in Uganda the presence of high orphan children in the study.
In contrary, the result of this study is higher than studies conducted in Thailand 2.92 per 100 children in years of observation and India 4.4 per 100 children years of observation. This difference might be due to socio cultural and economic difference (35, 36). The other possible explanation is the presence more ART service decentralization in India. Additionally, in Thailand there is a difference in operational definition of LTFU (use 12 months to say LTFU) and study period difference (6 years). Plus to this, the result of this study is higher than studies conducted in Zimbabwe 4.92 per 100 children in years of observation, Kenya 3.29 per 100 children years of observation and Ethiopia 3.6 per 100 children years of observation (37, 38, 39).This is might be due to variation in implementation of retention in care strategy and also follow up period difference (5 years) and in Ethiopia the difference might be study period difference (six years).
In this study, LTFU before 18 months (with incidence rate of 6.6 per100 children years of observation) was higher than LTFU after 18 months of ART initiation (6.1 per100 children years of observation). This is due to the fact that at initial time they are risk for immune reconstitution inflammatory syndrome and drug side effect that increase the risk of death. The incidence rate of lost to follow up at first year (6.9 per 100 children years of observation) was higher as compared to the second year (5.9 per 100 children years of observation). This is in line with the study conducted in South Africa(19). This is might be health care workers give repeated counseling for caregivers about the benefit of ART treatment and consequence of discontinuation. The other possible explanation might be government give attention and create awareness for the community about the benefit of treatment and decentralization of ART services.
The cumulative incidence of this study was 20.7% (CI = 17.20, 23.80).This is in line with the studies conducted in West Africa 21.8%, Nigeria 19% and Ethiopia 17.9%(13 34, 37). However, this result is higher than studies conducted in Asia 4.1%, Cote divore 9.3%, East Africa 14%,South Africa 9% and Zambia 16%(16, 22). This is might be due to economic and socio demographic difference and variation in implementation of retention strategy. For example, in Zambia health care workers apply home-to-home visit. In contrary, the finding of this study is lower than studies conducted in Mozambique 38.7% and in Adama Ethiopia 34%(40, 41).This might be in Mozambique study conducted in 10 rural districts and there was a challenging of transportation and poor health care infrastructure. In Adama Ethiopia study includes both pre ART initiation and post ART initiation.
In this study, the hazard of loss to follow up among children whose age between 1–5 years were 1.6 times higher than children whose age greater or equal to five years. This is supported by studies conducted in Thailand and Botswana (35, 41). This is due to this age group was more risk for malnutrition and opportunistic infection that increase disease progression rapidly(42). This result is inconsistent with a comparative analysis study conducted in Asia and Africa and study conducted in South Africa (16, 19).
This study showed that being male was 2.1 times increasing the hazard of loss to follow up as compared to female. This is consistent with studies conducted in Kenya, South Africa and Brazil (19, 27, 37).This is due to most of 152 (59.4%) of males initiate ART with advanced stage of diseases (III and IV).
Having advanced clinical stage (WHO stage III and IV) at the time of ART initiation was significantly increased the hazard of loss to follow up among children. This is supported by studies conducted in West Africa, Malawi, Uganda, Botswana and Ethiopia (24, 41, 43, 44, 45) .
The possible explanation might be children initiate ART in advanced stage increase the risk of opportunistic infections that cause morbidity and mortality that leads to unregistered death. Moreover, children at advanced stage may develop drug side effects especially with in the first six months and further complicate disease progression (46).
On the other hand, the result of this study is inconsistent with studies conducted in South Africa and Kenya (34, 37). The possible explanation might be patients with stage I and II not feel sick enough to accept restrictive medical care(47). Additionally, in South Africa children in this stage were asymptomatic and health care workers were not given more attention than those had advanced disease (34).
Children whose nutritional status was stunted were more hazardous to loss to follow up as compared to those whose nutritional status was normal. This is supported with studies conducted in other part of Africa country include Ethiopia (22, 26, 40). This could be due to the fact that stunted children may have had poor baseline health and poor ART compliance as compared to normal. In fact HIV by itself affects nutritional status and malnourished children more affected by HIV and increase disease progression (48, 49). Furthermore, stunted children may have had concomitant opportunistic infection that detained them back from the health facility for refill of drug and some may have died from such condition(50).
Regarding to adherence to ART, those having poor adherence to ART were about seven times increase the hazards of loss to follow up as compared to those having good adherence to ART. Also the hazardous of LTFU among children who had fair adherence to ART were 2.2 times higher than their counter part. This is the fact that poor/fair adherence increase viral load duplication and decrease drug effectiveness. Because of this, further suppression of immune system and increase opportunistic infection that rapidly increase disease progression(51). The other possible explanation might be poor medication adherence cause HIV viral resistance and subsequently treatment failure. Moreover, children depend on their caregiver to get their care due to this, if the child had poor improvement caregiver’s might be feel hopelessness or carelessness and loss from treatment cascade.
Furthermore, children whose regimen was not changed were four times more hazardous to loss to follow up as compared to those whose regimen was changed. This is might be most of old regimens have side effects that cause advanced disease and complication that leads to death. For example AZT containing regimen cause anemia that increase the disease progress (52).