Patient selection: infection with Plasmodium falciparum, with gametocyte clearance on days 1, 2 or 3 after completing therapy (the day of clearance was termed the parasite clearance time).
NOTE: Patients with persistent gametocytes (did not clear on days 1, 2 or 3) probably have a drug-resistant strain. These patients were excluded from the study.
Parameters for evaluating the patient from days 3 to 21 after completing therapy:
(1) gametocyte density on day 3
(2) gametocyte density on day 7
(3) gametocyte density on day 14
(4) gametocyte density on day 21
gametocyte density in gametocytes per µL blood =
= ((number of gametocytes per 200 WBC if number >=10) OR (number of gametocytes per 500 WBC if number per 200 WBC < 10)) * (WBC count 8000 per µL)
where:
• The authors assumed that the patients had a WBC count 8,000 per µL. The ideal situation would be to perform a WBC count each day along with the gametocyte count.
area under the curve for circulating gametocytes =
= ((7 - 3) * ((density day 3) + (density day 7)) / 2) + ((14 - 7) * ((density day 7) + (density day 14)) / 2) + ((21 - 14) * ((density day 14) + (density day 21)) / 2)
average AUC per day =
= (average under the curve) / (21 - 3) =
= ((2 * (density day 3)) + (5.5 * (density day 7)) + (7 * (density day 14)) + (3.5 * (density day 21))) / 18
Risk factors for persistent circulating gametocytes:
(1) delayed clearance of gametocytes (disappearance on day 2 or 3 vs none seen on day 1)
(2) presence of mutations associated with resistance to the chemotherapeutic regimen
Differential diagnosis for appearance of gametocytes: re-infection
