Do the small blood cells have a big impact as prognosticators in dengue – A study

© 2020 Published by Innovative Publication. This is an open access article under the CC BY-NC license (https://creativecommons.org/licenses/by-nc/4.0/)


Introduction
Dengue caused by dengue virus (DENV), is endemic in India and a cause of public health concern due to high mortality of severe forms. It can manifest as asymptomatic, mild to severe dengue. 1, 2 The milder forms presenting as flu like fever have overlap with other diseases like Influenza, Malaria etc and sometimes evolve rapidly to severe dengue with or without warning signs. Bleeding & shock are dreaded complications of severe dengue. [1][2][3] Dengue needs to be diagnosed early as there is no specific therapy. 3,4 Clinical features are of limited utility in diagnosing impending rapidly developing severe dengue and have to be supplemented by certain lab tests for accurate and early diagnosis of progression. [2][3][4][5][6][7] Severe dengue is characterized by thrombocytopenia (<1 lakh/cumm) preceding rise in hemocrit. 2,3,6,7 Thrombocytopenia is a consistent feature in dengue and a major reason for hospitalisation due to the risk of bleeding. 1,8 Complete blood counts including platelet counts are routinely performed simple, inexpensive tests available even in rural areas, where it may be checked by microscopy. There is confusion about the role of platelet counts in dengue, while it is confirmed as an initial dengue marker and are of the diagnostic criteria for dengue haemorrhagic fever(DHF), 8,9 correlation with severity of bleed and complications in dengue is debated in various studies. 10-16

Aims a nd Objectives
To study patterns of platelet count, its association with other lab parameters in dengue.

Materials and Methods
This study was conducted in hematology section over one month in November 2016 on 132 serologically https://doi.org/10.18231/j.jdpo.2020.056 2581-3714/© 2020 Innovative Publication, All rights reserved. 286 Introduction: Dengue is an arboviral disease endemic in India. Severe dengue has a high morbidity. The progression to severe dengue may be diagnosed by clinical and lab parameters, are of the useful lab tests is platelet count, as thrombocytopenia is a consistent feature in dengue. There is confusion about the role thrombocytopenia in dengue. Our study aims to study the platelet count patterns and its relevance to severity of dengue. Materials and Methods: We conducted a study on 132 dengue positive cases with relevant hematology data in November 2016. Results: We had predominance of young people and males in the study group. Thrombocytopenia was uniform across the ages and sexes. Severe thrombocytopenia constituted 56%, had significant association with atypical lymphocytosis, rise in hematocrit and antibody patterns. Conclusion: Platelet counts are marker of dengue, can serve as predicators of severity, platelet count monitoring helps guide transfusion therapy.
positive dengue cases. The data retrieved from hematology (complete blood counts tested by Sysmex 1800i) and microbiology records (dengue serology) was tabulated, along with visual check of platelets differential counts on leishman stained smears (as per hospital protocol) and analysed.

Inclusion criteria
All serologically positive dengue cases with thrombocytopenia and other relevant hematology data.

Exclusion criteria
Dengue cases with associated diseases, incomplete hematology data, high or normal platelet counts and pseudothrombocytopenia.

Ethical committee clearance
The study maintains anonymity of patient identity by recording only age & gender against the unique hospital identification number along with relevant data. The study was approved by ethical committee of hospital.

Results
Our study showed an age range of 5months to 65yrs with an average of 32yrs, with male predominance (male: female = 1.2:1)[ Table 1 ]. Thrombocytopenia was graded as and showed 55% paediatric, 56% adults, 57% males and 55% females had severe thrombocytopenia.
The analysis of severe thrombocytopenia [ Table 2 ] showed only one case <10,000/cumm (critical value) The lowest platelet count noted in adult females was 8,000/ µl as against 11,000/ µl in adult males and in paediatric group. The maximum cut off in thrombocytopenia was 1.3lakhs/ µl with an average of 69,000/µl.

Discussion
Thrombocytopenia is a prominent feature in dengue. It is a WHO criteria for DHF. 8,11,17 Cause for thrombocytopenia includes Platelet consumption, activation by surface band C3 + Ig G with complement moderated lysis, peripheral sequestration, destruction due to antibodies against viral antigens on platelets and direct damage to megakaryocyte precursors with decreased production 1,4,5,11,14,17 .
Thrombocytopenia impacts management raising concerns about transfusions, their effects and hospitalisation 1,7,8,10,16 . Our study showed a predominance of dengue in young age and males in accordance with few studies 5,12,16 .
Thrombocytopenia patterns showed predominance of severe cases in accordance with few 9,18,19 and discordance with other studies 17,20 . Severity being uniform between sexes and all ages. 15 35% of thrombocytopenia were transfusion triggers according to few 8,14,16 57  11  41  13  42  66  50  Normal  27  36  15  55  18  58  60  45  Low  05  07  01  04  00  00  06  05  Total  74  100  27  100  31  100 132 100   studies. 21 We had one case of critical thrombocytopenia in concordance with few 22 , discordance with other studies. 15 The average platelet count was similar to few, 10,16 varied in others. 7,8 Our study was in agreement with authors noting lower platelet counts, severity of dengue in females 13,22,23 than males and in adults than children 5,20 , other varied. 8,24 Leucopenia noted in 38% in accordance with few, 15 varied in other 16,18 being associated with mild than severe thrombocytopenia in support of few studies claming association with dengue fever than severe dengue. 23 We had 62% cases of lymphocytosis with equal distribution in mild and severe thrombocytopenia in accordance with few studies, suggesting it was a consistent feature in the course of dengue, 4,12 other differed. 25 Significant atypical lymphocytosis, noted in 52%, had highest association with severe than mild thrombocytopenias and was in accordance with few studies indicating it to be a marker and severity prognosticator for dengue. 26,27 Rise in hematocrit (above reference for age and sex) was noted in 66/132, 11% showed >50% (cut off severitypredicator, 28 ) 8% showed ≥20% above baseline hematocrit in accordance with few 12 varied in other 4,29 . Rise in hematocrit is a severity predicator 30 and WHO criteria of severe dengue. 80% of severe thrombocytopenias had ≥20% above baseline hematocrit as against 20% with moderate and none with mild thrombocytopenias, suggesting that platelet counts could be severity predicators in accordance with few, 10,11,31 other disagree. 32 The study showed that thrombocytopenia was consistent through the course of dengue. We had 29% NS1 and 40% antibody patterns. Severe thrombocytopenia was noted in 22% of NS1 as against 43% of antibody patterns, in concordance with studies claiming platelet counts drop from 3 rd day to 10 th day and reach a nadir between 4 th -7 th day 5,8,11,14 . This is in agreement with studies indicating a rise in NS1 antigen from 1-5 days, IgM-3 rd -5 th day and IgG from 7 th day onwards. 2,33

Conclusion
We conclude thrombocytopenia is a prominent feature and initial marker in dengue. Young children and females are at risk population. It could be a useful prognosticator of severe dengue, especially in association with other lab features. Platelet transfusions instituted due to concern about the platelet count drop and haemorrhagic tendencies, are guided by a study of platelet count patterns which helps to avoid harmful, wasteful transfusions.

Source of Funding
None.

Conflict of Interest
None.