Performance and clinical usefulness of the Optimal-IT® test in the treatment of confirmed malaria cases in rural areas in Côte d'Ivoire.

Background: In Africa, malaria care is mostly based on clinical presumption and the general application of antimalarial treatment to all febrile episodes over several years. Treatment limited to confirmed cases might curb the practice of equating fever with malaria, antimalarial drug abuse and the extension of Plasmodium resistance, provided that powerful and reliable rapid diagnostic tests are used. This study aimed at determining the performances of the Optimal-IT^® test in the strategy for the exclusive treatment of uncomplicated malaria in rural areas.

Materials and methods: A prospective study conducted in the forest region of San Pedro, Côte d'Ivoire, included patients exhibiting clinical signs of uncomplicated malaria who gave their consent and benefited from thick blood film (TBF), blood smear (BS) and Optimal-IT^® (pLDH-based) test. Rapid diagnostic test (RDT) results were taken into consideration to decide on malaria treatment and then compared with TBF/BS results (reference) to assess the performances and clinical usefulness of the RDT.

Results: The mean age of the 384 patients included (209 men, 175 women) was 28 years and the mean temperature was 38.1°C. TBF/BS and Optimal-IT^® were concordant in 92% of patients but discordant in 10 false negative (3%) and 19 false-positive patients (5%). The average parasite density of P. falciparum was 25,600 trophozoites/μl. The performances calculated were: sensitivity=95%, specificity=91%, positive predictive value=90%, negative predictive value=95%, positive likelihood ratio=10, negative likelihood ratio=0.06 and diagnostic odds ratio=166, indicating that Optimal-IT^® is a powerful and credible diagnostic tool. The 193 RDT-positive patients treated were healed, despite three recurrence cases at day (D) D₁₇, D₂₅ and D₂₇, respectively. RDT-negative patients received various treatments (antibiotics, paracetamol), but two patients among them presented with a bout of malaria on D₇. None of the previously untreated patients returned with severe malaria.

Conclusions: The Optimal-IT^® test, which is already used in the field, showed good performances to effectively detect patients with and without malaria. It is therefore adapted to the malaria treatment strategy limited to confirmed cases.