Clinical, haematological and radiological predictors of severe dengue in the paediatric population

Background: Dengue is a mosquito borne viral infection which has higher morbidity and mortality in the paediatric age group than in the adult group. Objectives: To assess the clinical and haematological parameters for early diagnosis and better management of severe dengue (SD). Method: A prospective observational study was conducted in the Department of Paediatrics, FH Medical College, Agra, India from September 2021 to February 2022. Confirmed dengue cases aged 1 month to 18 years were included in the study. Cases were classified into two groups, non-severe dengue (dengue fever and dengue with warning signs) and SD. All cases had complete history, clinical examination, and relevant investigations. Bivariate analysis was performed using Chi-square test and p value <0.05 was considered significant. Results: A total of 801 confirmed cases of dengue, admitted in FH Medical College, were included in study. Of them, 564 had non-severe dengue and 237 had SD. Clinical features like gastrointestinal bleeding, lethargy, low pulse pressure, altered consciousness, ascites, bilateral pleural effusion and oliguria were significantly higher in SD as compared to non-severe dengue (p-value <0.05). Haematological parameters like severe thrombocytopenia, raised haematocrit (HCT), liver transaminase levels, deranged prothrombin time (PT) / international normalised ratio (INR), hypoalbuminaemia and radiological features like bilateral pleural effusion and ascites were significantly associated (p-value <0.05) with SD.


Introduction
Dengue fever (DF) is a mosquito-borne arboviral infection caused by the dengue virus (DENV) which has four different serotypes. Patients infected with DENV have a wide spectrum of clinical manifestations, ranging from asymptomatic to severe dengue (SD), including dengue haemorrhagic fever (DHF) and dengue shock syndrome (DSS) 1,2 . Incidence and mortality from dengue are increasing globally with each passing year 3 . Around 1.8 million of the population which is at risk for dengue live in endemic countries of the South East Asia Region 3 . Without proper treatment, the case fatality rate in SD is more than 20% and with timely intervention, it can be reduced to less than 1% 4 . A major dengue epidemic was seen in India in 2021 during which Uttar Pradesh recorded a 10-fold increase in the number of reported cases (over 20,000) 5 .
A peculiarity of DENV infection is that infection by one serotype produces serotype-specific lifelong immunity; however, instead of giving protection or remaining neutral against other serotypes, a secondary infection by a heterogeneous serotype often results in severe disease by a mechanism called antibody dependent enhancement (ADE) 6 . DSS mortality is reported to be 50 times higher than that of DF 7 . SD is a leading cause of serious illness and death among children in some Asian and Latin American countries 8 . Patients with dengue illness can sometimes develop unusual manifestations such as involvement of liver, kidneys, brain or heart with or without evidence of fluid leakage. Such unusual manifestations may be associated with co-infections and co-morbidities and are mostly a result of prolonged shock leading to organ failure. These atypical features, if found, are defined as 'expanded dengue syndrome' 9 . Management of dengue with warning signs or SD requires hospital admission and judicious fluid management along with supportive therapy. As SD has a high mortality and morbidity and there is no specific management available, early detection of clinical and haematological parameters helps in early diagnosis and management.

Objectives
To assess the clinical and haematological parameters for early diagnosis and better management of SD

Method
This prospective observational study was conducted in the department of paediatrics of FH Medical College, Agra, India, from September 2021 to February 2022.

Inclusion criteria:
 Children diagnosed clinically as DF aged 1 month to 18 years.  Cases confirmed based on the presence of NS1 antigen and/or IgM or IgG antibody by rapid immunochromatography and enzyme-linked immunosorbent assay.

Exclusion criteria:
 Children with pre-existing chronic illness or any concurrent fever causing illness such as malaria, typhoid or urinary tract infections.  Children discharged before clinical recovery and those with co-infections.  Parents refused to allow the children to participate in study.
Children satisfying inclusion criteria were recruited to the study. A detailed history was taken and a complete physical examination was done, including all vital parameters. Cases were classified according to the World Health Organisation (WHO) classification of dengue 1  Probable dengue  Dengue with warning signs  Severe dengue The relevant investigations recorded were total white blood cell (WBC) count, platelet count, haematocrit (HCT), transaminases level, prothrombin time (PT)/international normalised ratio (INR), chest x-ray and ultrasonography (USG) of abdomen. Other investigations like magnetic resonance imaging (MRI) of brain and cerebrospinal fluid (CSF) analysis were done when required. Criteria used to define laboratory parameters are as follows: [10][11][12] 1. Haemoconcentration: More than 20% increase in HCT from baseline 2. Leucocytosis -Peripheral WBC count more than for age 3. Leucopenia -Peripheral WBC count less than 5000/µL 4. Elevated serum aspartate transaminase (AST) / alanine transaminase (ALT) -more than 40U/L 5. Deranged PT/INR -as per age 6. Hypoalbuminaemia -< 2.5 mg/dl Patients were followed up daily for development of new symptoms, signs, or complications till discharge/death. Blood counts were repeated every 24 hours till defervescence of fever. Subsequently, patients were divided into two groups and various clinical, haematological and radiological features were compared in the two groups.
Group 1 -Non severe dengue -Included are probable dengue and dengue with warning sign Group 2 -Severe dengue. . Written informed consent was obtained from the parents of the participating children and assent from the children over 12 years of age.

Statistical analysis:
Descriptive data are presented as numbers or percentages. Comparison of the groups for categorical variables was done by Chisquare test. Descriptive statistics were reported as percentages and means when applicable along with standard deviation. Data were analysed using SPSS software. A two-tailed p-value smaller than 0.05 was considered statistically significant

Results
A total of 801 children were admitted with dengue over the study period. All the children were included in the study. Table 1 shows the demographic profile of the dengue cases. Children of age group 6-10 years constituted the highest percentage (38.5%) of total cases. However, SD was more common in children between 1-5 years and they constituted 47.7% of the total SD cases.
The 801 children with dengue were categorized according to the WHO classification as shown in Table 2.   Table 3 shows the clinical manifestations of the cases. Clinical features such as erythema, abdominal pain, anorexia, vomiting, hepatomegaly, respiratory distress, splenomegaly, oedema, altered sensorium, jaundice, oliguria, ascites, lethargy, low pulse pressure and gastrointestinal bleeding were significantly associated with SD compared to nonsevere dengue.

Discussion
In the present study, the most commonly affected age group was 6-10 years, while the incidence of SD was more in the 1-5-year age group. In contrast, studies by Reddy A, et al 13 and Jain H 14 found the 5-10-year age group to be significantly associated with SD. Children aged 1-5 years presenting with SD could be due to an immaturely developed immune system. SD was more common in males as compared to females in this study which was similar to studies by Reddy A, et al 13  This gender difference can be due to the relatively more exposed body surface area. Children from urban areas were affected more than children from rural areas probably because urban lifestyle is more commonly associated with breeding of mosquitoes, which was similar to studies by Suresh A, et al 16 and Shah PS, et al 17 . In our study, 29.7% children had SD which was comparable to a study by Afroze S, et al 15 who reported 32% cases of SD. However, the study by Jain H 14 found 12.3% of SD cases, which might be due to a relatively small sample size.
Erythema was significantly associated with SD, similar to a study by Reddy A, et al 13 . Another important observation in the study was the statistically significant association of lethargy with SD. Meta-analysis conducted by Tsheten T, et al 18 also showed that lethargy was significantly associated with the severity of dengue. In our study, vomiting, abdominal pain and jaundice were associated with SD which was similar to studies by In our study, bleeding manifestations like epistaxis were not associated with SD, whereas gastrointestinal bleeding was significantly associated with SD which was similar to the study by Tsheten T, et al 18 . Central nervous system (CNS) manifestations like altered sensorium were significantly associated with SD. There were similar findings in studies by Afroze S, et al 15  On serology, 78.1% cases were NS1 positive, and majority were non-severe dengue whereas 21.8% cases were NS1 and IgM or IgG positive. Children with positive NS1 along with IgG were significantly associated with SD. It signifies re-infection of dengue associated with SD. Similar findings were seen in the study by Afroze S, et al 15 . On chest xray, bilateral pleural effusion was associated with SD, which was similar to the study by Reddy GC, et al 22 , On USG of abdomen, ascites was the common finding associated with SD. There was a similar finding in the study by Pothepragada S, et al 25 on univariate analysis. Unlike the present study, a study by Malleshappa K, et al 20 suggested ascites and pleural effusion were not significantly associated with SD. They found perinephric oedema was significantly associated with dengue severity.
In haematological parameters, a predominant feature of dengue was thrombocytopenia. Suggested mechanisms that contribute to thrombocytopenia in dengue include reduced thrombopoiesis through bone marrow suppression and increased platelet clearance in peripheral blood. Regarding reduced thrombopoiesis, hematopoietic suppression is a well-known phenomenon during DENV infection. A marked bone marrow hypocellularity is described at onset of the febrile phase with pancytopenia, including megakaryocytes 26 . Severe thrombocytopenia (<50,000 platelets/cu mm) was significantly associated with SD. A study by Sreenivasan P, et al 27 showed thrombocytopenia between 40,000 to <100,000 platelets/cu mm was significantly associated with SD. There were similar findings in a study by Nandwani S, et al 28 where the initial platelet count (<20,000/cu mm) was significantly associated with mortality. In our study, about 48.4% of the total population had severe thrombocytopenia whereas bleeding manifestation such as epistaxis and gastrointestinal bleeding were 12% and 15% of total cases respectively and there was no correlation between severe thrombocytopenia and bleeding manifestations. Similar findings were seen in studies by Avasthi S, et al 29 31 . Neither leucocytosis nor leucopenia was significantly associated with dengue severity in this study, which was similar to a study conducted by Arora SK, et al 19 .
The strength of the study was a good sample size to represent the population. One limitation of the study was that it was confined to a single tertiary care centre; hence there could be a selection bias and observational bias. Another limitation is that some patient samples were taken after fluid resuscitation was done in cases of emergencies which can result in error of HCT values. Larger prospective studies are needed to validate the findings observed in this study. Virus serotyping also was not done.

Conclusions
In this study, clinical features like erythema, abdominal pain, vomiting, jaundice, cough, hepatosplenomegaly, severe bleeding, lethargy, low pulse pressure, altered consciousness, ascites and bilateral pleural effusion were significantly associated with severe dengue compared to non-severe dengue. Haematological parameters like severe thrombocytopenia, raised HCT, raised transaminase levels and deranged PT/INR and hypoalbuminemia were also significantly associated with severe dengue.