Table 3.

Common sources for misdiagnosis of CQR and CQS Plasmodium vivax

	Explanation	Recommendation
Incorrect diagnosis of CQS
Enrollment of patients without clinical disease	Host immunity in asymptomatic patients enrolled from cross-sectional surveys, may facilitate clearance of parasitaemia even following partially effective drug treatment	Restrict efficacy trials to patients presenting with clinical disease
Coadministration of early PQ	Early PQ has schizontocidal activity that can increase parasite clearance and prevent recrudescent infections	Primaquine treatment should be delayed until the end of the follow-up period
Short duration of follow-up	Early evidence of resistance is manifest by late recrudescence	Patients should be followed up for a minimum of 28 days
Incorrect diagnosis of CQR
Incomplete treatment course	From poor patient adherence	Supervision of drug treatment
Dose of chloroquine administered too low	Prescription of inadequate mg/kg dose	Documentation of exact dose of drug administered
Poor absorption of drug	Either from poor quality drug, reduced gastrointestinal absorption	Measurement of drug blood concentrations on day 7 and the day of parasite recurrence
Poor drug quality	Faulty product	Confirmation of adequate drug levels, pharmacologic evaluation of study drugs, and purchase only from certified, trusted producers
Inadequate sample size	Leading to wide confidence intervals of high failure rates derived from very few cases	Recruitment of an adequate sample (> 70 patients)

CQR = chloroquine resistant; CQS = chloroquine sensitive; PQ = primaquine.