Determinants of Parasite Clearance Time among Plasmodium knowlesi Patients in Malaysia

Abstract

Plasmodium (P.) knowlesi infection was only recently discovered in 2004, and since then the number of cases has increased each year. As such, there is still a need to understand the clinical management of P. knowlesi infection to ensure control of the disease. Therefore, this work was performed to determine factors that affect the clinical outcome of P. knowlesi infected patients. A cross-sectional study from 2012 to 2016 was conducted in Hospital Kuala Lipis, Pahang, Malaysia. The main clinical outcome was parasite clearance. A total of 72 P. knowlesi patients were included, which were mostly male (n=56, 77.80%), with a mean age of 37.39±14.61 years. Fifty-six patients (77.80%) were prescribed with artemisinin-based antimalarial following diagnosis, while the remaining patients (n=16, 22.20%) were treated with chloroquine. The length for parasite clearance of P. knowlesi was 4(4-5) days [(median (IQR)]. Factors that affect the primary outcome of the study (>4 days for parasite clearance) was then determined. A multivariate logistic regression demonstrated that significant predictors of parasite clearance were initial parasite levels and number of symptoms (χ2=11.97, df(69), P=0.003). Those with an initial parasite count of > 2 400/uL were 4.8 times more likely to take > 4 days for parasite clearance (P=0.02). Having < 4 symptoms increased the odds of > 4 days for parasite clearance by 0.14 times (P=0.02). This study shows the need to closely monitor patients with higher initial parasite counts (> 2400/uL) and patients with > 4 symptoms associated with P. knowlesi infection, to ensure appropriate treatment is administered.