Background: Antiretroviral drugs are used for Human Immunodeficiency Virus (HIV)
infection prevention as well as long-term therapy. Use of these drugs is essential in
reducing HIV infection prevalence and improving the quality of life of people living with
HIV infection. Availability and access is thus very important. Uninterrupted supply can
be achieved through routine forecasting and supply planning. Forecasting for paediatric
antiretroviral (ARV) drugs is complex due to the fact that dosing is weight-based, a
suitable range of paediatric drug formulations is lacking and paediatric ARV drugs are
not packaged in monthly dosage requirements. Forecast accuracy, consumption
monitoring and timely supply planning are key elements to uninterrupted supply.
Objectives: The objectives of the study were to determine forecast accuracy for
paediatric antiretroviral drugs in Kenya; determine relative proportions of children at
various weight categories and on various antiretroviral regimen and formulations;
determine within and between-individual changes over time with regards to weight and
formulation; and identify factors that influence choice of ARV formulations dispensed to
paediatric patients from the pharmacy personnel perspective.
Methodology: Forecast accuracy was calculated using Mean Absolute Percentage Error
(MAPE) for periods 2010/11, 2011/12 and 2012/13. Retrospective longitudinal cohort
design was used to determine effect of age, weight and sex on antiretroviral formulations
dispensed to children at a selected public health facility in Kenya. In-depth interviews
were done to establish factors that influence choice of ARV formulation dispensed to
children. Forecast and consumption data was collected. Univariate, bivariate and repeated
measures logistic regression data analysis was done. A point of concept saturation
approach was used for qualitative data analysis.
Results: Forecast accuracy for seven paediatric ARV formulations was established for
2010/11, 2011/12 and 2012/13 forecast periods. Forecasts were found to be inaccurate
for abacavir/lamivudine 60/30mg; zidovudine/lamivudine 60/30mg; zidovudine/
lamivudine/nevirapine 60/30/50mg; efavirenz 200mg; Lopinavir/ritonavir 80/20mg and
zidovudine 10mg/ml where MAPE ranged between 11.8% and 2198.9%. NVP 10mg/ml
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was the only product that recorded reasonable forecasts where MAPE of “41.6%, 49.1%
and 24.4% was observed in 2010/11, 2011/12 and 2012/13, respectively”. Forecast errors
were found to be non-random. For repeated measures data, majority of the children were
males and constituted 171(55.0 %), 171(55.9 %) and 169(55.8 %) in July 2010, 2011 and
2012, respectively. Median and interquartile (IQR) range for age were 9.2(6.8, 12.0),
9.6(7.3, 12.0) and 10.3(7.5, 12.5) years in July 2010, 2011 and 2012, respectively.
Median and IQR range for weight were 26(20, 32), 27(21, 32) and 28(21, 34) Kg in July
2010, 2011, 2012, respectively. 55.0 %, 61.5% and 64.9 % of children were in the ≥25
Kg weight category in July 2010, 2011 and 2012, respectively. Only 19.0 %, 30.3 % and
32.6 % of children were on paediatric formulations for period 2010/11, 2011/12 and
2012/13. The study revealed that children were likely to turn 25 Kg at age 8 years. Male
children were found to be more likely to use adult formulation than female children.
Dispensing staff reported weight, age, paediatric ARV drug availability; and preference
to dispense paediatric ARV formulation as factors that influenced choice of drug
dispensed to children below 15 years.
Conclusion: Forecasts for abacavir/lamivudine 60/30mg; zidovudine/lamivudine
60/30mg; zidovudine/ lamivudine/ nevirapine 60/30/50mg; efavirenz 200mg; lopinavir/
ritonavir 80/20mg and zidovudine10mg/ml were inaccurate in 2010/11, 2011/12 and
2012/13. Only nevirapine 10mg/ml had accurate forecast across the three periods. The
forecast errors were found to be non-random. The forecast did not take into account sex
and age as important variables that determine formulations dispensed to children.
Dispensing staff reported drug availability and their preference to dispense particular
formulations as factors that influenced choice of ARV drug they dispensed to children.
Recommendations: There is need for evidence based forecasting where data on
variables that are required for forecasting are continually collected and reviewed against
consumption patterns. In addition, it would be necessary for forecast performance to be
monitored on quarterly or bi-annual basis for early detection and correction of errors. Use
of different forecasting approaches and models would be important in comparing forecast
performance