From: Determinants of relapse periodicity in *Plasmodium vivax* malaria

Consider two groups of patients who represent two extremes | |
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Without radical treatment group A has an 80% relapse rate (eg some soldiers who fought in the Pacific in the Second World War)
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Without radical treatment group B has a 20% relapse rate (eg some soldiers who fought in the Korean War)
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Assuming a fixed fractional proportion of relapses and no acquisition of immunity, then the total number of relapses/100 patients is | |

group A = 395, | group B = 24. |

These numbers represent the of viable activatable hypnozoites (VAH) i.e. there are 16 times more in group A compared to group B. It is likely that the distribution of VAH is random among the patients and therefore conforms to a Poisson distribution.
minimum number | |

If primaquine at a dose of 0.25 mg base/kg (15 mg adult dose) reduces the number of viable activatable hypnozoites (VAH) by 90%, and there is no difference in susceptibility between the groups, and this effect is consistent across all patients then the post treatment number of VAH is | |

group A = 39 or 40 | group B = 2 or 3. |

Thus we would expect 13 to 20 times more relapses in group A compared to group B. | |

This hypothetical example simply points out that the apparent differences in primaquine "resistance" may reflect differences in the biology of the parasite rather than drug susceptibility per se. |