Background: Hematological abnormalities are a well-recognized hallmark of malaria, but Plasmodium vivax has traditionally been regarded as a benign infection. This study aimed to determine the prevalence of hematological abnormalities in P. vivax malaria and to compare parameters before and after standard antimalarial therapy.

Methods: In this single-centre, cross-sectional observational study conducted at a tertiary care hospital in Kolkata, 99 patients aged 12–60 years with slide- and/or antigen-positive P. vivax malaria were enrolled after applying pre-specified exclusion criteria. Complete blood counts and related indices were recorded at presentation (Day 1) and after treatment (Day 7 and Day 30). Categorical variables were compared using the chi-square test, with p<0.05 considered significant.

Results: The cohort was predominantly male (77.8%), with a mean age of 36.85 years. Anemia was present in 69.7% of patients (64.9% of males, 90.9% of females; p=0.036) and was predominantly normocytic normochromic. Thrombocytopenia was found in 81.8% of patients, most commonly of moderate severity, without bleeding manifestations. Leucopenia was seen in 25.3% and lymphopenia in 30.3% of patients; leucocytosis, neutropenia, eosinophilia, and monocytosis were infrequent. All parameters showed significant improvement by Day 30: mean hemoglobin rose from 11.41 to 12.66 g/ dL, mean platelet count from 114.6×10³/µL to 191.2×10³/µL, and the proportion with anemia, thrombocytopenia, and leucopenia declined significantly over time (all p<0.05).

Conclusion: P. vivax malaria is associated with a substantial burden of anemia and thrombocytopenia at presentation, both of which improve significantly with standard antimalarial therapy. These findings reinforce that P. vivax should not be regarded as a uniformly benign infection and support the diagnostic value of routine hematological screening in patients with fever from malaria-endemic areas.

KEYWORDS: Plasmodium Vivax, Malaria, Anemia, Thrombocytopenia, Leucopenia, Hematological Abnormalities.