From a weighing scale to a pole: a comparison of two different dosage strategies in mass treatment of Schistosomiasis haematobium

BACKGROUND: Clinical schistosomiasis in endemic countries is treated with a single dose of praziquantel per 40 mg/kg body weight. Treating according to weight, in resource-poor settings when thousands of doses are to be administered in mass treatment campaigns, is considered problematic. A calibrated dose-pole based on height was developed and is now used in mass treatment campaigns for determining the doses for schoolchildren. The dose-pole will generate dose errors since every child population contains individuals that are either short or tall for weight. The aim of this study is to explore whether the WHO praziquantel pole is a satisfactory dose instrument for mass treatment of S. haematobium. METHODS: In 1996 and 2002, 1,694 children were surveyed in the Kilimanjaro Region, Tanzania. We compared doses given by weight to doses given by height using descriptive statistics and regression. CONCLUSIONS AND INTERPRETATION: The WHO dose-pole for praziquantel is based on height of the patient; however, children with the same height will differ in weight. Our study shows that children with the same weight could qualify for up to four different dose levels based on their height. The largest variation of doses based on the WHO dose-pole will be found in children below 20 kg of bodyweight. Using bodyweight and tablet halves as the smallest tablet division unit to determine the doses of praziquantel, one only has to identify every 6th kilogram of bodyweight; the doses will then vary a lot less than when using the WHO dose-pole.