Field trial of the RTM dipstick method for the rapid diagnosis of malaria based on the detection of Plasmodium falciparum HRP-2 antigen in whole blood.

The performance of the Quorum RapidTest Malaria (RTM) dipstick method that detects Plasmodium falciparum histidine-rich protein-2 (PfHRP-2) antigen in whole blood was evaluated in a malaria endemic area. Results were compared with conventional Giemsa-stained blood films. Of 306 people tested 37.9% (116/306) were found to be parasitaemic; of these 66.4% (77/116) were P. vivax and 32.8% (38/116) were P. falciparum infections. There was only one (0.9%) mixed P. falciparum plus P. vivax infection. The RTM test was positive in 35/36 patients with P. falciparum identified on blood smear examination, resulting in a sensitivity of 97.2% [95% confidence interval (CI): 91.6-102.8%]. Specificity was 96.3% (95% CI: 93.9-98.6%). The RTM test had a positive predictive value of 77.8% (95% CI: 65.7-89.9%) and a negative predictive value of 99.6% (95% CI: 98.4-100.8%). Of the 10 false positives, seven reported recent malaria episode and treatment, indicating persistence of antigenaemia. If these were assumed truly infected, the positive predictive value is increased to 93.3% (95% CI: 85.8-100.8%). The RTM test was positive in all seven P. falciparum infections with gametocytes and one mixed infection, but was negative in all falciparum gametocytes and relapsing fever cases. All but one P. vivax infection gave negative result on the RTM test. The RTM test missed one patient with parasitaemia. The test is highly sensitive and specific requiring no instrument or trained personnel. It appears to be a very useful tool for rapid diagnosis of malaria, especially in the rural health institutions with limited diagnostic facilities.

Comparison of rectal artemisinin with intravenous quinine in the treatment of severe malaria in Ethiopia.

OBJECTIVE: To compare the clinical efficacy and safety of artemisinin suppository with quinine injection. DESIGN: Comparative open randomised study. SETTING: A government regional referral hospital in Ethiopia. SUBJECTS: Sixty five adult patients of both sexes: 32 for artemisinin and 33 for quinine with complicated severe falciparum malaria. MAIN OUTCOME MEASURES: Therapeutic responses and adverse reactions. RESULTS: The clinical and laboratory data in both groups of patients on admission were comparable. The parasite clearance time (PCT), fever subsidence time (FST) and coma resolution time (CRT) were shorter in the artemisinin treated group. There was no significant different in the parasitological cure rates in both arms of treatment. No correlation was observed between the initial parasite density and PCT or FST in both groups of treatment. Mortality rates were similar both in the artemisinin and quinine groups. The common adverse effects observed in most patients receiving quinine, in an increasing order of occurrence were; vomiting, dizziness, hypoglycaemia and tinnitus, which were all relatively rare with artemisinin. Some patients treated with artemisinin showed tenesmus which was not observed in any patient treated with quinine. CONCLUSION: The rectal artemisinin is more efficacious and safer than the intravenous quinine. Thus, artemisinin may be considered a potential drug which can replace quinine in the treatment of severe malaria in Ethiopia provided it is made available at affordable prices.

Rapid diagnosis of severe malaria based on the detection of Pf-Hrp-2 antigen.

Blood samples collected from 34 patients with severe malaria who were involved in antimalarial treatment studies were tested with rapid dipstick assay (Rapid Test Malaria, RTM from Quorum Diagnostics Inc., Vancouver, BC, Canada), based on the detection of Histidine Rich Protein (HRP-2) of Plasmodium falciparum. This was compared with the conventional Giemsa stained thin and thick blood smears. The study was done from March 1998 to May 1998, at the Basic Research Laboratory of the Faculty of Medicine, Addis Ababa University. Comparable number of patients (n = 32) with various diagnosis other than falciparum malaria were used as controls. The rapid dip-stick assay was positive in 31 among 34 of the severe malaria cases with sensitivity of 91.2%, specificity of 93.7%, positive predictive value (PPV) of 93.9% and negative predictive value (NPV) of 90.9%. The three cases missed by the RTM, had parasitemia of 66,000, 44,000, and 40,000/microL of blood which might be due to genetic heterogeneity of the HPR-2 expression. Among the controls, there were 2 false positive cases which may be as a result of persistent HPR-2 antigen after the clearance of peripheral parasitemia. The dip-stick method is a very quick, sensitive and specific diagnostic tool with limits of detection comparable or better than those provided by the light microscopy. The simplicity of the technique makes this method more applicable in the resource deprived laboratories of developing countries provided the kit is affordable for large scale use.