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

Figures & data

Table 1 Doses of praziquantel in numbers of 600 mg tablets by height in cm according to the WHO dose-pole

Height (cm)	Number of tablets
94–109	1
110–124	1.5
125–137	2
138–149	2.5
150–159	3
160–178	4
>178	5

Modified after WHO (1).

Table 2 Mean values, standard deviations, coefficients of variation, minimum and maximum values for the variables age, weight and height among the 1,477 schoolchildren

Variable	Mean	Sd	CV	Min.	Max.
Age in years	11.0	2.82	25.6	5	18
Weight in kg	27.3	8.02	29.4	14	65
Height in cm	130.4	12.88	9.9	99	170

Fig. 1 A scatter plot of height in cm and weight in kg for 1,477 schoolchildren with a correlation coefficient (r) of 0.9.

Fig. 2 Theoretical deviations in mg/kg according to body weight, illustrated by trajectories, when 40 mg/kg is the target dose and 300 mg tablet halves are used as the smallest dose unit.

Table 3 Praziquantel doses according to weight applied to the weight range of 1,477 schoolchildren when tablet halves are used as the minimum segments

Weight (kg)	Number of tablets
12–18	1
19–26	1.5
27–33	2
34–41	2.5
42–48	3
49–56	3.5
57–63	4
64–71	4.5

Fig. 3 Frequency weighted scatter plot with doses in number of pills from the dose-pole on the horizontal axis and number of pills by weight on the vertical axis with both the line of equality and the fitted line included.

Fig. 4 Frequency weighted scatter plot of the differences in doses on the y-axis against the mean values of doses on the x-axis when comparing doses given by the dose-pole and doses using the weight approach. Reference lines included for mean differences as well as the limits of agreement.

Table 4 Deviations in mg/kg from the target dose of 40 mg/kg, and number and percentage of children using the WHO dose-pole and the weight approach with tablet halves

		Number and proportion of children with different extent of deviation from target dose when
Dose classification	Deviation from target (mg/kg)	Using the dose-pole	%	Using weight	%
	41–45	1	0.1
Higher than	36–40
target	31–35	1	0.1
	26–30
	21–25	4	0.3
	16–20	44	3.0
	11–15	89	6.0
	6–10	406	27.5	63	4.3
	1–5	508	34.4	629	42.6
On target	0	53	3.6	89	6.0
	1–5	301	20.4	648	43.9
Lower than	6–10	66	4.5	48	3.2
target	11–15	2	0.1
	16–20	2	0.1

Fig. 5 Dose by the dose-pole and dose by weight and tablet halves in mg/kg, all according to bodyweight.

Fig. 6 Histograms of doses given by the dose-pole for each dose given by the weight and halves approach.

Fig. 7 Theoretical distribution of doses (mg/kg) in the case of an accurate scale and when the scale overestimates the weight by 2 kg.

Table 5 Theoretically determined doses according to weight using tablet halves as the standard minimum dose fraction based on the weight of the child and with a dose never below 40 mg/kg

Weight (kg)	Number of tablets
12–18	1
19–26	1.5
27–33	2
34–41	2.5
42–48	3
49–56	3.5
57–63	4
64–71	4.5
72–79	5
80–87	5.5

Table 6 Theoretically determined doses based on the weight of the child using tablet halves as the standard minimum tablet fraction and resulting in doses that are never below 40 mg/kg

Weight (kg)	Number of tablets	Max. dose (mg/kg)
12–15	1	50.0
16–22	1.5	56.3
23–30	2	52.2
31–37	2.5	48.4
38–45	3	47.4
46–52	3.5	45.6
53–60	4	45.3
61–67	4.5	44.3
68–75	5	44.1
76–82	5.5	43.4
83–90	6	43.4