A simple method for assessing quinine pre-treatment in acute malaria

Administration of a loading dose of quinine in severe malaria may be dangerous if therapeutic blood concentrations are already present because of previous treatment. To assess the reliability of the history of pretreatment we conducted a prospective study of 379 adult patients with acute falciparum malaria admitted to a hospital in western Thailand. Admission plasma concentrations of quinine were measured by high performance liquid chromatography (HPLC), and compared with the patients' history of previous quinine treatment. The sensitivity of the history was 59% (95% confidence interval [CI] 49–69%), the specificity was 79% (95% CI 74–84%), the positive predictive value was 53%, and the negative predictive value 82%. A rapid (10 min) semi-quantitative estimate of plasma quinine concentrations, based on a simple ‘dipstick’ method using a quinine-specific monoclonal antibody, proved considerably more sensitive and specific. The correlation between the dipstick estimate and the subsequent HPLC measurement of plasma quinine concentration was 0.85 (n = 404; P < 0.0001). In 404 admission samples, the negative predictive value of the dipstick estimate for plasma quinine concentrations >1 μg/mL was 100%. In Thailand the history of previous quinine treatment given by the patients or their relatives was unreliable but the quinine dipstick provided a simple and rapid means of assessment of quinine pre-treatment in acute falciparum malaria.