European Journal of Cardiovascular Medicine

Dengue fever, caused by the dengue virus (DENV) and transmitted primarily by the Aedes aegypti mosquito, is a rapidly escalating global health concern, particularly in tropical and subtropical regions. In recent years, India has witnessed a marked surge in dengue cases, making it one of the most affected countries worldwide. The disease presents with a wide clinical spectrum, ranging from mild febrile illness to life-threatening complications such as dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS). The unpredictable nature of the illness, especially in its early stages, poses significant diagnostic challenges for clinicians.^1-4

Haematological parameters play a pivotal role in the clinical assessment of dengue. Key findings such as thrombocytopenia, leukopenia, and hemoconcentration not only aid in the preliminary diagnosis but also serve as important prognostic indicators. These laboratory markers are critical in distinguishing dengue from other acute febrile illnesses, particularly in endemic areas where overlapping clinical symptoms are common. Timely recognition of these changes can guide appropriate monitoring, supportive care, and timely referral to prevent disease progression and reduce fatal outcomes.^5-9

In addition to individual patient management, understanding the haematological trends in dengue can also inform broader public health strategies. Regional variability in clinical presentation and laboratory abnormalities underscores the importance of localized studies. Factors such as environmental conditions, vector density, population immunity, and healthcare accessibility can influence disease expression. Therefore, a comprehensive assessment of haematological profiles in specific geographical settings is essential to strengthen early detection frameworks and improve case management protocols.

This study was conducted at Anugrah Narayan Magadh Medical College, Gaya, one of the leading tertiary care centers in Bihar, aims to evaluate the clinical and haematological profile of patients diagnosed with acute dengue infection, with the objective of identifying characteristic laboratory trends and their correlation with disease severity. The findings are expected to provide valuable insights for clinicians and public health professionals involved in the management and control of dengue in the region.

This observational, hospital-based study was conducted in the Department of Pathology in collaboration with the Department of Medicine at Anugrah Narayan Magadh Medical College, Gaya. The study period extended from July 2018 to March 2020 and included patients who presented with clinical features suggestive of acute dengue infection.

Study Population

Patients of all age groups and both sexes presenting with acute febrile illness and subsequently confirmed to have dengue infection through serological testing (NS1 antigen and/or IgM antibody positivity using ELISA) were included in the study. Informed consent was obtained from all participants or their legal guardians prior to inclusion. Patients with known hematological disorders, chronic liver disease, or other co-infections (e.g., malaria, typhoid, leptospirosis) were excluded to eliminate potential confounding variables.

Data Collection and Clinical Evaluation

A detailed clinical history was recorded for each patient, including demographic details, presenting symptoms, duration of fever, presence of bleeding manifestations, rash, and other systemic complaints. A thorough physical examination was performed with specific attention to signs of plasma leakage, hemorrhagic manifestations, hepatomegaly, and hypotension.

Laboratory Investigations

Venous blood samples were collected under aseptic conditions at the time of admission and analyzed for complete blood count (CBC) using an automated hematology analyzer. The haematological parameters assessed included hemoglobin concentration, total leukocyte count, differential leukocyte count, hematocrit, and platelet count. Serial monitoring of these parameters was done wherever applicable. Additional tests such as liver function tests and coagulation profiles were conducted as clinically indicated.

Diagnostic Criteria

Diagnosis of dengue was confirmed based on clinical presentation and positive serological testing for NS1 antigen and/or dengue-specific IgM antibodies, in accordance with the guidelines issued by the World Health Organization (WHO). The severity of dengue was classified into three categories: Dengue Fever (DF), Dengue Hemorrhagic Fever (DHF), and Dengue Shock Syndrome (DSS), based on WHO criteria.

Data Analysis

Collected data were systematically entered into Microsoft Excel and analyzed using standard statistical software. Descriptive statistics such as mean, standard deviation, and percentages were used to summarize quantitative variables. Comparisons between haematological parameters across different severity groups of dengue were made using appropriate statistical tests such as the Student’s t-test and chi-square test. A p-value of less than 0.05 was considered statistically significant.

Ethical Considerations

The study protocol was reviewed and approved by the Institutional Ethics Committee of Anugrah Narayan Magadh Medical College, Gaya. Patient confidentiality and ethical standards were strictly maintained throughout the study period.

The study enrolled 280 patients with confirmed dengue infection (NS1 antigen and/or IgM antibody positive) between July 2014 and March 2016. The mean age was 33.8 ± 14.5 years, with a predominance of young adults (18–40 years), accounting for 50% of cases. Children and adolescents (<18 years) made up 30%, while those above 40 years constituted 20%. A male predominance was noted, with a male-to-female ratio of 3:2, indicating a higher exposure or vulnerability among males, possibly due to occupational and behavioral factors. Furthermore, 70% of the cases were from urban areas, reflecting the greater prevalence of Aedes aegypti mosquitoes in densely populated urban environments where breeding habitats like stagnant water are more common.

Table 1: Demographic Characteristics of Dengue Patients (N=280)

All 280 patients presented with fever (100%), reaffirming its role as a universal symptom in dengue infection. Myalgia (80%) and headache (70%) were also prominent symptoms, followed by rash (40%) and gastrointestinal symptoms such as vomiting. Bleeding manifestations were reported in 30% of patients, with petechiae being the most common form, followed by epistaxis and gum bleeding. Hepatomegaly was noted in 20% of cases, and hypotension in 12.1%, particularly among those with severe dengue. Signs of plasma leakage, such as pleural effusion or ascites, were evident in 16.1% of patients and were more common in DHF and DSS, underlining their diagnostic importance in severe forms.

Table 2: Clinical Features of Dengue Patients (N=280)

Baseline hematological investigations revealed key abnormalities in dengue patients. The mean hemoglobin was 13.4 ± 1.7 g/dL, while the hematocrit averaged 40.8 ± 5.0%, with 46% of patients demonstrating elevated values (>40%), indicating hemoconcentration. Thrombocytopenia (platelet count <150,000/μL) was present in 82% of patients, with a mean count of 82,000/μL. Leukopenia (TLC <4.0 ×10³/μL) was observed in 58% of cases. Differential counts showed neutrophil predominance, with mean neutrophil and lymphocyte percentages of 61% and 29.5%, respectively. These parameters highlight the characteristic hematological profile of acute dengue, with low white cell and platelet counts serving as important early indicators.

Table 3: Hematological Parameters at Admission (N=280)

When analyzed by severity, significant trends were evident across dengue categories (DF, DHF, DSS). Patients with severe disease (DHF and DSS) had significantly higher hematocrit levels, indicating greater plasma leakage and hemoconcentration (mean 42.5% and 46.0% vs. 38.8% in DF; p<0.001). Correspondingly, platelet counts decreased markedly with increasing severity (108,000 in DF vs. 58,000 in DHF and 32,000 in DSS; p<0.001), confirming that thrombocytopenia is a strong indicator of disease progression. Total leukocyte counts also dropped significantly with severity, suggesting increased immune activation or marrow suppression in severe cases. These findings were statistically significant and align with established pathophysiology of severe dengue.

Table 4: Hematological Parameters Across Dengue Severity Groups

Serial platelet monitoring among 112 patients with DHF and DSS revealed a gradual recovery pattern. On admission (Day 1), the mean platelet count was 52,000/μL, with 67.9% of patients having counts below 50,000/μL. By Day 3, the count rose to 68,000/μL, with a notable reduction in severe thrombocytopenia cases (42.9%). Platelet levels improved further on Days 5 and 7, reaching a mean of 138,000/μL by Day 7, with only 3.6% of patients remaining severely thrombocytopenic. This trend illustrates the natural course of recovery with supportive treatment and reinforces the utility of serial monitoring in clinical decision-making, particularly for discharge planning and transfusion support.

Table 5: Serial Monitoring of Platelet Count in Severe Dengue Cases (DHF/DSS, n=112)

A clear association was observed between bleeding manifestations and specific hematological abnormalities. Patients with bleeding (n=112) had significantly lower platelet counts (mean 48,000/μL) compared to those without bleeding (102,000/μL; p<0.001). Hematocrit levels were also higher among bleeding patients (44.0% vs. 38.5%; p<0.001), reflecting plasma leakage and hemoconcentration. Additionally, total leukocyte counts were lower in the bleeding group (3.1 ×10³/μL vs. 4.9 ×10³/μL; p<0.001). These findings emphasize that severe thrombocytopenia and elevated hematocrit are significant predictors of bleeding risk, thus serving as critical markers in early identification of high-risk patients requiring intensive monitoring.

Table 6: Correlation of Hematological Parameters with Bleeding Manifestations

The present study, conducted at Anugrah Narayan Magadh Medical College, Gaya over a span of 20 months, provides an in-depth analysis of the clinical and haematological profile of patients with acute dengue infection. A total of 280 serologically confirmed dengue cases were evaluated to assess key demographic trends, symptomatology, laboratory abnormalities, and their association with disease severity. The findings not only reinforce the classical clinical picture of dengue but also underline the importance of haematological parameters as diagnostic and prognostic tools in routine clinical practice.

A notable demographic trend observed in this study was the predominance of dengue among young adults (18–40 years), who accounted for half of all cases. This is in agreement with earlier reports from endemic regions of India and Southeast Asia, where the highest incidence is observed among the economically active population. The male predominance (male-to-female ratio of 3:2) could be attributed to greater outdoor exposure among men, increasing their likelihood of mosquito bites. Urban residents comprised 70% of the cases, likely due to higher vector density, inadequate urban sanitation, and environmental factors conducive to Aedes aegypti breeding, such as stagnant water in domestic and peri-domestic settings.

Fever was universal among all patients, reaffirming its status as a cardinal symptom of dengue. Myalgia and headache were the next most common complaints, consistent with the classical “breakbone fever” description of dengue. Rash, bleeding manifestations, and gastrointestinal symptoms were more frequent in moderate to severe disease categories. Importantly, bleeding manifestations such as petechiae, gum bleeding, and epistaxis occurred in nearly one-third of patients, and were significantly associated with more severe disease (DHF/DSS). Hepatomegaly and signs of plasma leakage were observed in 20% and 16.1% of patients respectively, indicating the need for vigilant clinical examination to identify early complications.

The hematological profile at admission showed hallmark features of dengue infection—thrombocytopenia (82%), leukopenia (58%), and elevated hematocrit (46%) indicating hemoconcentration. These findings are well-established indicators of dengue and correlate with capillary leakage and bone marrow suppression, two key pathogenic processes in dengue virus infection. The mean platelet count of 82,000/µL, coupled with leukopenia and rising hematocrit, underlines the value of these parameters in triaging patients during outbreaks.

Analysis of disease severity (DF, DHF, DSS) revealed statistically significant trends across hematological parameters. Hematocrit was markedly elevated in DHF and DSS (mean 42.5% and 46.0%, respectively) compared to DF (38.8%), suggesting that hemoconcentration correlates strongly with plasma leakage and severe illness. Likewise, platelet counts declined with increasing severity, with DSS patients having dangerously low mean counts of 32,000/µL. The progressive leukopenia from DF to DSS further reflects the underlying immunosuppression and marrow involvement in severe dengue. These associations were statistically significant (p<0.001), underscoring the prognostic value of routine blood counts in predicting disease severity.

Among patients with severe disease (DHF/DSS), serial monitoring of platelet counts showed a steady upward trend, with substantial recovery by Day 7 in the majority of cases. On admission, nearly 68% had counts below 50,000/µL, a threshold commonly associated with bleeding risk. By Day 5, this percentage had dropped to 16%, and by Day 7, only 3.6% remained severely thrombocytopenic. These observations support the self-limiting nature of thrombocytopenia in dengue and highlight the importance of monitoring trends rather than isolated values. This is particularly relevant in avoiding unnecessary platelet transfusions, which should be reserved for clinically indicated cases.

A crucial aspect of this study was the correlation of bleeding manifestations with hematological parameters. Patients who developed bleeding had significantly lower platelet counts (mean 48,000/µL) and higher hematocrit levels (mean 44%) compared to those without bleeding. Additionally, their total leukocyte counts were markedly lower. These findings align with studies by Kumar et al. and Narayanan et al., who also reported strong associations between thrombocytopenia, hemoconcentration, and bleeding risk. Such correlations reinforce the value of early hematological profiling in identifying patients at greater risk for complications, thereby guiding more targeted monitoring and intervention.

The findings from this study have important clinical and public health implications. In resource-constrained settings where advanced diagnostics may not be readily available, simple yet reliable hematological markers like platelet count, hematocrit, and TLC can aid early diagnosis, risk stratification, and timely referral. Understanding the regional pattern of disease presentation and severity, as shown in this Bihar-based cohort, also helps in tailoring local guidelines and preparing healthcare infrastructure for outbreak management.^10-13

Moreover, the observed trends emphasize the need for community awareness and vector control, especially in urban settings. The high prevalence of disease among young and productive individuals further highlights the socio-economic burden posed by dengue and the urgent need for integrated public health interventions including surveillance, early diagnosis, and supportive care.

This study underscores the critical role of clinical and haematological evaluation in the early identification and effective management of acute dengue infections. The findings highlight that thrombocytopenia, leukopenia, and hemoconcentration are not only common laboratory features but also significant prognostic indicators of disease severity and bleeding risk. A clear correlation between declining platelet counts, elevated hematocrit levels, and clinical severity—from dengue fever to DHF and DSS—reaffirms the utility of these parameters in guiding clinical decision-making. The recovery pattern observed through serial platelet monitoring further validates the importance of supportive care and careful observation, minimizing the need for unnecessary interventions. Given the urban predominance and higher disease burden among young adults, targeted public health strategies including vector control, public education, and early diagnostic support are essential. This region-specific data from Bihar contributes valuable insight to the national dengue surveillance landscape and can aid clinicians and policymakers in formulating more effective, evidence-based approaches to dengue prevention and control.

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