Clinical spectrum and complications of Plasmodium vivax malaria: A retrospective study from Delhi, India

Background. Plasmodium vivax malaria, traditionally regarded as benign, is now recognised to cause severe illness. India bears a high burden of P. vivax malaria, yet data on its clinical spectrum and severity predictors remain limited. This study aimed to describe the clinical and laboratory profile of P. vivax malaria and identify risk factors for severe disease in a tertiary care setting. Materials and Methods. A retrospective study of 361 patients diagnosed with P. vivax malaria between June 2020 and May 2024 was conducted at a tertiary hospital in South Delhi, India. Diagnosis was confirmed by peripheral smear and/or rapid diagnostic tests. Patients were categorised into complicated and uncomplicated groups using WHO criteria. Demographic, clinical, and laboratory data were analysed with chi-square test, odds ratios, correlation analysis, and logistic regression. Results. Of 361 patients, 167 (46.3%) had complications. Mean age was 31 years with male predominance (64.6%), though complications were more frequent in females (42% vs. 32%, P=0.039). Anaemia (73.4%), thrombocytopenia (57.9%), and leucocytosis were common. Thrombocytopenia (OR 3.20, P<0.001) and leucocytosis (OR 2.37, P<0.05) were significantly linked to severity. Elevated creatinine (OR=6.07, P 0.001) and hyperbilirubinemia (OR=3.71, P<0.001) strongly correlated with complications. Breathlessness and pleural effusion were also more common in severe cases. Strong associations were observed between anaemia and hyperbilirubinemia (r 0.75), bleeding and ARDS (r 0.82), and mortality with shock (r=0.74). Conclusion. Nearly half of P. vivax cases developed severe complications, challenging its benign perception. Anaemia, thrombocytopenia, leucocytosis, and organ dysfunction were key severity markers. Higher complication rates in females and afebrile cases highlight diagnostic and social challenges. Early recognition of atypical features and vigilant monitoring are crucial to improve outcomes in endemic regions.