RISK-FACTORS OF CHLOROQUINE RESISTANCE IN PLASMODIUM-FALCIPARUM MALARIA

Objective: To identify patient-related risk factors of chloroquine res istance.Design: A case control study. Subjects: Plasmodium falciparum infected school children were followed prospectively for 7 days for th e detection of chloroquine resistance. Cases were 38 individuals with chloroquine resistant infections. Controls were 125 individuals with c hloroquine sensitive infections. Cases were compared with controls wit h respect to previous or current study factor levels. Subjects were re cruited from randomly selected schools which were stratified for area. Study location was in North Guadalcanal, Solomon Islands. Outcome mea sure: Treatment failure of chloroquine in standard dosage (25 mg/kg). Follow-up period was 7 days. Results: Logistic regression resulted in 5 independent significant predictors of chloroquine resistance, obtain ed simultaneously with the diagnosis of malarial infection: (i) Young age (odds ratio (OR) for age <7 years: 7.1; 95% confidence interval (C I): 2.5-25.0; OR per year increase after the age of 5 years: 0.8; 95% CI: 0.6-0.9). (ii) High parasite density (OR for > 1000/mu l: 5.0; 95% CI: 2.0-10.6; OR per 500 parasites/mu l increase: 1.3; 95% CI: 1.1-1. 7). (iii) Normal spleen size (OR: 4.0; 95% CI: 1.5-10.8). (iv) Malnutr ition (OR: 4.9; 95% CI: 1.8-13.2). (v) Presence of gametocytes in the thick smear (OR: 3.0; 95% CI: 1.1-8.0). Conclusion: The identified ris k factors are easily measureable without special equipment. They may b e useful for health workers in the Solomon Islands, even in remote are as, to identify Plasmodium falciparum infected individuals at high ris k for chloroquine resistance before a treatment decision is made.