Effect of Adjustments on the Forecast Accuracy of Anti-Retroviral Medicines in Uganda

Abstract

Background: Outputs from the quantifications are used to advocate and allocate funding and develop supply plans to ensure the availability of medicines. However, the actual consumption is not always equal to the forecast, and thus forecasting teams often adjust further to improve the forecast accuracy. The study aimed to determine the forecast accuracy of the final forecast, the effect of adjustments, and the factors that affect the forecast accuracy of ARVs in Uganda. Methods: A descriptive study was conducted using quantitative and qualitative data collection methods. The statistical forecasts, final forecasts, and actual consumption data from January 2016 to December 2018 were collected retrospectively from the Ministry of Health and the web-based ordering and reporting system (WAOS). Microsoft Excel was used for data analysis. The mean average percentage error (MAPE) was used to measure forecast accuracy, and a student t-test was used to determine the significance of adjustments. Key informant interviews were done to determine the factors affecting forecast accuracy. Thematic approach was used to analyse qualitative data. Results: The national final forecast MAPE ranged from 2.33% to 5.15% (Jan 2016 -Jan 2019), while the statistical MAPE ranged from 2.65% to 4.31% (Aug 2017 - Jan 2019). The MAPEs for adult ARVs were generally lower than those of pediatric ARVs, and a variation in forecast accuracy with one of the central warehouses was noted. Adjustments generally lowered the MAPE for adult ARVs but increased the MAPE for most pediatric ARVs. Adjustments were significant for 53.8% (n=13, p=0.05) of the ARVs. Factors including dispensing practices, the complexity of the quantification, adherence to treatment guidelines, data quality, product availability, and quantification team attributes were identified to affect the forecast accuracy Conclusions: The final and statistical forecasts had good accuracy, and adjustments improved the accuracy of adult ARV forecasts while decreasing the accuracy for pediatric ARVs. The accuracy of the forecast was affected by the quantification complexity, product usage, availability, and team attributes. Forecast accuracy of new drugs and the degree of significance of the factors affecting forecasting should be studied further. Trial registration: Not Applicable