Revisiting the circulation time of Plasmodium falciparum gametocytes: molecular detection methods to estimate the duration of gametocyte carriage and the effect of gametocytocidal drugs

Table 2 Other parameters used or estimated in density and prevalence models using QT-NASBA data

Parameter	Description	Estimates (95% CI)
		Kenya, 2003-2004	Tanzania, 2006
Density model
1/ρ	1/duration of gametocyte sequestration, days	1/11	1/11
S ₃ *	size of sequestered gametocyte population on day 3 that is subsequently released into the circulation	Non-ACT: 0.0263 ACT: 0.0013	0.0013 (0.0001-0.0237)
G ₃ ^¶	density of circulating gametocytes/μL on day 3 after start treatment	non-ACT: 1.45 (0.44-4.74) ACT: 0.13 (0.03-0.52)	ACT: 1.88 (0.37-9.52) ACT-PQ: 0.07 (0.01-0.86)
Prevalence model
1/f ^¥	time until patients gametocyte-negative on day 0 become gametocyte-positive, days	5.60	5.60 (1.06-29.4)

All values with confidence intervals were estimated in the model; values without confidence intervals were fixed unless stated otherwise.
* estimated based on the trial data, expressed as the total sequestered population that would be released per μL of blood. Details of the sensitivity analysis for this parameter are given in table S1. The value presented here is a product of the baseline sequestered gametocyte density and the immediate impact of anti-malarial drugs on days 0, 1 and 2.
^¶estimated based on the data for each trial and treatment arm separately. The density of circulating gametocytes at enrolment was not different between arms within trials (table 1). The value presented here is a product of the baseline gametocyte density and the immediate impact of anti-malarial drugs on days 0, 1 and 2.
^¥Estimated from the data in the trial in Kenya. The number of children who became gametocytaemic during the trial while being gametocyte negative at enrolment was 3 (out of 4 gametocyte negative individuals) for non-ACT in Kenya, 9 (out of 12) for ACT in Kenya, 2 (out of 6) for ACT in Tanzania and 0 (out of 4) for ACT-PQ in Tanzania.

ISSN: 1475-2875