Methods to discriminate primary from secondary dengue during acute symptomatic infection

Abstract Background Dengue virus infection results in a broad spectrum of clinical outcomes, ranging from asymptomatic infection through to severe dengue. Although prior infection with another viral serotype, i.e. secondary dengue, is known to be an important factor influencing disease severity, current methods to determine primary versus secondary immune status during the acute illness do not consider the rapidly evolving immune response, and their accuracy has rarely been evaluated against an independent gold standard. Methods Two hundred and ninety-three confirmed dengue patients were classified as experiencing primary, secondary or indeterminate infections using plaque reduction neutralisation tests performed 6 months after resolution of the acute illness. We developed and validated regression models to differentiate primary from secondary dengue on multiple acute illness days, using Panbio Indirect IgG and in-house capture IgG and IgM ELISA measurements performed on over 1000 serial samples obtained during acute illness. Results Cut-offs derived for the various parameters demonstrated progressive change (positively or negatively) by day of illness. Using these time varying cut-offs it was possible to determine whether an infection was primary or secondary on single specimens, with acceptable performance. The model using Panbio Indirect IgG responses and including an interaction with illness day showed the best performance throughout, although with some decline in performance later in infection. Models based on in-house capture IgG levels, and the IgM/IgG ratio, also performed well, though conversely performance improved later in infection. Conclusions For all assays, the best fitting models estimated a different cut-off value for different days of illness, confirming how rapidly the immune response changes during acute dengue. The optimal choice of assay will vary depending on circumstance. Although the Panbio Indirect IgG model performs best early on, the IgM/IgG capture ratio may be preferred later in the illness course

A Prognostic Model for Development of Profound Shock among Children Presenting with Dengue Shock Syndrome

<div><p>Purpose</p><p>To identify risk factors and develop a prediction model for the development of profound and recurrent shock amongst children presenting with dengue shock syndrome (DSS)</p><p>Methods</p><p>We analyzed data from a prospective cohort of children with DSS recruited at the Paediatric Intensive Care Unit of the Hospital for Tropical Disease in Ho Chi Minh City, Vietnam. The primary endpoint was “profound DSS”, defined as ≥2 recurrent shock episodes (for subjects presenting in compensated shock), or ≥1 recurrent shock episodes (for subjects presenting initially with decompensated/hypotensive shock), and/or requirement for inotropic support. Recurrent shock was evaluated as a secondary endpoint. Risk factors were pre-defined clinical and laboratory variables collected at the time of presentation with shock. Prognostic model development was based on logistic regression and compared to several alternative approaches.</p><p>Results</p><p>The analysis population included 1207 children of whom 222 (18%) progressed to “profound DSS” and 433 (36%) had recurrent shock. Independent risk factors for both endpoints included younger age, earlier presentation, higher pulse rate, higher temperature, higher haematocrit and, for females, worse hemodynamic status at presentation. The final prognostic model for “profound DSS” showed acceptable discrimination (AUC=0.69 for internal validation) and calibration and is presented as a simple score-chart.</p><p>Conclusions</p><p>Several risk factors for development of profound or recurrent shock among children presenting with DSS were identified. The score-chart derived from the prognostic models should improve triage and management of children presenting with DSS in dengue-endemic areas.</p></div

Assessment of Microalbuminuria for Early Diagnosis and Risk Prediction in Dengue Infections

<div><h3>Background</h3><p>Dengue is the most important arboviral infection of humans. Following an initial febrile period, a small proportion of infected patients develop a vasculopathy, with children at particular risk for severe vascular leakage and shock. Differentiation between dengue and other common childhood illnesses is difficult during the early febrile phase, and risk prediction for development of shock is poor. The presence of microalbuminuria is recognized as a useful early predictor for subsequent complications in a number of other disorders with vascular involvement. Significant proteinuria occurs in association with dengue shock syndrome and it is possible that early-phase microalbuminuria may be helpful both for diagnosis of dengue and for identification of patients likely to develop severe disease.</p> <h3>Methodology/Principal Findings</h3><p>We measured formal urine albumin to creatinine ratios (UACRs) in daily samples obtained from a large cohort of children with suspected dengue recruited at two outpatient clinics in Ho Chi Minh City, Vietnam. Although UACRs were increased in the 465 confirmed dengue patients, with a significant time trend showing peak values around the critical period for dengue-associated plasma leakage, urine albumin excretion was also increased in the comparison group of 391 patients with other febrile illnesses (OFI). The dengue patients generally had higher UACRs than the OFI patients, but microalbuminuria, using the conventional cutoff of 30 mg albumin/g creatinine discriminated poorly between the two diagnostic groups in the early febrile phase. Secondly UACRs did not prove useful in predicting either development of warning signs for severe dengue or need for hospitalization.</p> <h3>Conclusion/Significance</h3><p>Low-level albuminuria is common, even in relatively mild dengue infections, but is also present in many OFIs. Simple point-of-care UACR tests are unlikely to be useful for early diagnosis or risk prediction in dengue endemic areas.</p> </div

Score-chart for prediction of profound shock.

<p>The upper panel assigns a point score for each risk factor while the lower panel assigns the predicted risk of developing profound shock based on the total point sum for all risk factors.</p

Adjusted effects of candidate predictors on clinical outcomes (full logistic model and reduced model with variable selection) in all study participants (N = 1207).

<p>Performance of the associated prediction models (based on repeated ten-fold cross-validation [internal validation] and temporal validation) is shown at the bottom of the table.</p><p>DSS: dengue shock syndrome</p><p>Effects are summarized as odds ratio (95% confidence interval).</p><p>Interaction tests between gender and hemodynamic index were significant for recurrent shock (p = 0.01) and profound DSS (p = 0.01)</p><p>All performance measures were corrected for optimism using 10-times 10-fold cross-validations.</p><p>Adjusted effects of candidate predictors on clinical outcomes (full logistic model and reduced model with variable selection) in all study participants (N = 1207).</p

Baseline characteristics and outcomes of study participants (N = 1207).

<p>Summary statistics are median (interquartile range) for continuous variables and frequency (percentage) for categorical variables. n refers to the number of subjects with non-missing values.</p><p>AST: aspartate aminotransferase</p><p>DSS: dengue shock syndrome</p><p>^a including petechiae (775/1207), bruising and purpura (39/1207)</p><p>^b including epistaxis/gum bleeding (17/1207) and gastrointestinal/vaginal bleeding (26/1207)</p><p>^c detected by clinical assessment</p><p>^d includes 89 patients presenting with hypotensive/decompensated shock who had ≥1 recurrent shock episode, 129 patients presenting with compensated shock who had ≥2 recurrent shock episodes, and 4 patients treated with inotropic drugs after their first episode of recurrent shock.</p><p>Baseline characteristics and outcomes of study participants (N = 1207).</p

Frequency of adverse clinical outcomes over time for the patients enrolled in the study (N = 1207).

<p>The numbers shown below the line graphs indicate the total number of DSS cases enrolled in the study each year.</p

Longitudinal dynamics of UACRs in the confirmed dengue and OFI patient groups.

<p>All patients from Clinic A, and the confirmed dengue patients from Clinic B, are included. A significant time trend was observed in the dengue patients (p<0.0001), peaking on day 5 of illness, but no trend was apparent in the OFI patients (p = 0.22). The grey lines represent the evolution of the UACRs over time for each patient. The blue lines correspond to loess scatter plot smoothers.</p

Clinical and laboratory characteristics for the confirmed dengue and OFI patients groups.

<p>Continuous variables are summarized as median (interquartile range); categorical variables are summarized as frequency (%).</p><p>Missing values for:^(a) up to 3, ^(b) 5, ^(c) 9, ^(d) 12, ^(e) 20, ^(f) 48 cases.</p><p>OFI: other febrile illness.</p>*<p>If present, the severity of clinical symptoms was evaluated each day by study physicians using a pre-defined three point scale. For this analysis participants were considered to have persistent vomiting or severe abdominal pain if they scored two or more on the relevant scale, on any day during the acute illness.</p