Lower Low-Density Lipoprotein Cholesterol Levels Are Associated with Severe Dengue Outcome

<div><p>Dengue virus (DENV) is a flavivirus of worldwide importance, with approximately 4 billion people across 128 countries at risk of infection, and up to 390 million infections and 96 million clinically apparent cases estimated annually. Previous <i>in vitro</i> studies have shown that lipids and lipoproteins play a role in modifying virus infectivity. However, the relationship between development of severe dengue and total cholesterol, high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C), respectively, is unclear. We analyzed data from 789 laboratory-confirmed dengue cases and 447 other febrile illnesses (OFI) in a prospective pediatric hospital-based study in Managua, Nicaragua between August 2005 and January 2013, using three different classifications of dengue severity: World Health Organization (WHO) 1997, WHO 2009, and standardized intervention categories. Total serum cholesterol and LDL-C levels decreased over the course of illness and were generally lower with increasing dengue severity, regardless of classification scheme. Greater decreases in LDL-C than HDL-C were observed among dengue-positive patients compared to patients with OFI and among severe dengue compared to mild dengue cases. Furthermore, daily cholesterol levels declined with daily albumin blood levels. To examine the effect of cholesterol at presentation on subsequent risk of development of severe dengue, relative risks and 95% confidence intervals were calculated using multivariable modified Poisson models. We found that lower total serum cholesterol and LDL-C levels at presentation were associated with subsequent risk of developing dengue hemorrhagic fever/dengue shock syndrome using the WHO 1997 dengue severity classification, and thus that the reduction in LDL-C is likely driving the decreases observed in total serum cholesterol levels among dengue-positive patients. Our results suggest that cholesterol blood levels are important correlates of dengue pathophysiology and should be explored as part of a prognostic biomarker panel for severe dengue.</p></div

Eligibility flow chart.

<p>Of the 1,440 patients who presented to the hospital with suspected dengue, 1,236 met the eligibility criteria and were included in the analysis. Abbreviations: BMI, body mass index.</p

Age- and gender-adjusted marginal mean cholesterol levels (mg/dl) by dengue severity classification and day of illness.

<p>For the WHO 1997 classification, mild dengue was defined as DF and severe dengue was defined as DHF/DSS. For the WHO 2009 classification, mild dengue was defined as Dengue with and without Warning Signs and severe dengue was defined as SD. For the standardized intervention categories, mild dengue was defined as IC 1/IC 2 care and severe dengue was defined as IC 3 care. The day of fever onset was defined as day 1 of illness. <b>A</b>, <b>B</b>, <b>C</b>, Total serum cholesterol levels were significantly lower in patients who developed severe dengue compared to patients with mild dengue on days 5–7 of illness using the WHO 1997 classification (p<0.001), on days 4–8 of illness using the WHO 2009 classification (p<0.05), and on days 5–8 of illness using standardized intervention categories (p<0.05). Regardless of dengue outcome, total serum cholesterol levels decreased from day 2–6 and increased from day 6–8 of illness. <b>D</b>, <b>E</b>, <b>F</b>, LDL-C levels were significantly lower in patients who developed severe dengue compared to patients with mild dengue on days 5–7 of illness using the WHO 1997 classification (p<0.01), days 4–8 of illness using the WHO 2009 classification (p<0.05), and on day 2 and days 5–7 of illness using standardized intervention categories (p<0.05). Regardless of dengue outcome, LDL-C levels decreased from day 3–6 and increased from day 6–8 of illness. HDL-C levels were significantly lower in patients who developed severe dengue compared to patients with mild dengue on days 5–8 of illness using the WHO 1997 classification (p<0.01), days 3–8 of illness using the WHO 2009 classification (p<0.01), and days 4–8 of illness using standardized intervention categories (p≤0.05). Regardless of dengue outcome, HDL-C levels decreased from day 2–7 of illness before increasing slightly on day 8 of illness.</p

Characteristics of study participants by DENV infection status and disease severity classification criteria.

<p>Abbreviations: DENV, dengue virus; WHO, World Health Organization; OFI, other febrile illness; DF, dengue fever; DHF/DSS, dengue hemorrhagic fever/dengue shock syndrome; DWS, dengue with or without warning signs; SD, severe dengue; IC, standardized intervention categories.</p><p>Characteristics of study participants by DENV infection status and disease severity classification criteria.</p

Effect of cholesterol level at presentation on development of severe dengue outcome using the WHO 1997 disease severity classification.^*

<p>*Severe dengue outcome was modeled by cholesterol at presentation, age, gender, malnutrition and immune response using modified Poisson models with robust standard errors. For the WHO 1997 disease severity classification, severe dengue outcome was defined as DHF/DSS and mild dengue outcome, the reference group, was defined as DF.</p><p>Effect of cholesterol level at presentation on development of severe dengue outcome using the WHO 1997 disease severity classification.^{<a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0003904#t002fn001" target="_blank">*</a>}</p

Relative risk of DFCS and DFCS/DSS/DSAS in 2009–10 in DENV-3 cases, Hospital Study.

1<p>Relative risk for the events are adjusted for dengue season (2009–10 and 2010–11, with 2008–9 as reference), immune response (primary versus secondary DENV infection), age (<5 versus ≥5 years old), sex, and early presentation (≤3 days versus >3 days since onset of symptoms). Year 2009–10 emerged as the only significant risk factor in all models, with values as indicated.</p

Demographic and clinical characteristics of DENV-3 cases, Hospital Study, 2005–11.

1<p>In the hospital study, immune response is known in 109, 168, and 99 DENV-3 cases in years 2008–9, 2009–10, and 2010–11, respectively.</p>2<p>Hemorrhagic manifestations do not include laboratory values and are defined as presence of any of the following clinical signs and symptoms: petechiae, rash, positive tourniquet test, bruising, hematoma, hemoptysis, epistaxis, gingivorrhagia, melena, hematemesis, hematuria, subconjunctival hemorrhage, vaginal hemorrhage, hypermenorrhea and excessive bleeding at puncture site.</p>3<p>p-values were calculated using the Chi-square tests, except for mean age and mean day of presentation, for which Mann-Whitney t-tests were applied.</p

Presentation of signs of poor peripheral perfusion in hospital study dengue cases, 2005–9 vs. 2009–10.

<p><i>A</i>, cold extremities, <i>B</i>, poor capillary refill (>2 sec), and <i>C</i>, compensated shock. Left panel, frequency of presentation by day; right panel, Kaplan-Meier survival function adjusted for early presentation (days 1–3 after onset of fever).</p

Classification of severity among confirmed dengue cases by year.

<p>Dengue cases were classified according to WHO classification (Dengue Hemorrhagic Fever and Dengue Shock Syndrome), Dengue Fever with Compensated Shock (DFCS), and Dengue with Signs Associated with Shock (DSAS), in <i>A</i>, cohort study, 2004–10, and <i>B</i>, hospital study, 2005–10.</p

Multivariate analysis of risk factors for DFCS compared to other dengue cases, Hospital Study, 2005–10.

1<p>The reference group is years 2005–9.</p