Rising Biomarkers in the First Week Flag Deadly Heart Shock in SFTS Patients

Severe fever with thrombocytopenia syndrome, an emerging tick-borne viral illness, has long been known for its alarming fatality rate, but the precise mechanisms that push certain patients toward death have remained frustratingly opaque. A new retrospective study published in BMC Infectious Diseases now offers one of the clearest pictures yet of a particularly lethal complication: cardiogenic shock. Drawing on 775 laboratory-confirmed cases treated at Nanjing Second Hospital in China between April 2020 and December 2024, a team led by Jianshe Xu and Jing Xie traced how inflammatory, cardiac, renal, coagulation, and lipid markers behave in the days surrounding hospital admission, and used those trajectories to identify who is most likely to collapse into shock while there is still time to intervene.

The stakes of the question are stark. Cardiogenic shock, a state in which the heart can no longer pump enough blood to perfuse the body’s organs, occurred in 143 of the 775 patients, or 18.5 percent. More telling is how that figure maps onto mortality. Of the 164 patients who died in the hospital, 99, or roughly six in ten, had developed clinically adjudicated cardiogenic shock. The condition was not simply a marker of severity; it was the dominant final pathway for the majority of fatal outcomes, confirming that cardiac involvement is a central driver of death in this viral hemorrhagic-fever-like syndrome rather than a bystander phenomenon.

Timing proved to be one of the study’s most clinically consequential findings. The researchers found that most shock events clustered tightly within the first week after admission, with approximately 85 percent occurring by day seven. This early clustering defines what the authors describe as a clinically relevant surveillance window: a period during which intensive monitoring, aggressive fluid management, and readiness for cardiac support could plausibly alter outcomes. For clinicians managing SFTS in endemic regions of East Asia, where the disease is transmitted by ticks and, in some documented instances, through contact with infected blood, the implication is that the first seven days of hospitalization are when the battle is most often decided.

To disentangle which laboratory abnormalities genuinely predict shock, the team employed a layered statistical strategy. They began with univariable Cox regression to screen potential predictors, then applied least absolute shrinkage and selection operator analysis, a regularization technique that prunes redundant variables and guards against overfitting, before finalizing a multivariable Cox model. The result was a six-biomarker panel comprising interleukin-6, N-terminal pro-B-type natriuretic peptide, urea, fibrin and fibrinogen degradation products, triglycerides, and total cholesterol. Five of these rose with shock risk; the sixth, total cholesterol, moved in the opposite direction, with lower levels independently associated with greater danger.

The biological logic embedded in that panel is worth unpacking. Interleukin-6 is a master cytokine of the innate immune response, and its elevation signals the cytokine storm widely believed to underlie much of SFTS pathology. N-terminal pro-B-type natriuretic peptide is released by stretched or stressed heart muscle, making it a sensitive chemical barometer of cardiac strain. Urea points to declining kidney function, a frequent companion of circulatory collapse. Fibrin and fibrinogen degradation products indicate uncontrolled clot formation and breakdown, the signature of disseminated intravascular coagulation, while the lipid abnormalities, rising triglycerides and falling cholesterol, suggest both deranged metabolism and the consumption of lipoproteins as they bind and neutralize circulating endotoxin-like products during severe inflammation.

Because single time-point measurements can miss the dynamics of a rapidly evolving illness, the researchers also modeled biomarker trajectories over the first fourteen days using locally estimated scatterplot smoothing, a flexible nonparametric technique that reveals trends without imposing a rigid mathematical form. Patients who went on to develop shock showed sustained upward trajectories in their inflammatory, cardiac, renal, and coagulation markers, while their lipid markers declined in a time-dependent fashion. In other words, shock was not announced by a single alarming lab value but by the direction and persistence of change across multiple organ systems simultaneously, a pattern the authors frame as multisystem dysregulation.

The study also applied restricted cubic spline models to characterize how continuous biomarker levels relate to shock risk. These spline approaches allow the relationship between exposure and outcome to bend and curve rather than forcing a straight line, which matters in medicine where thresholds and nonlinear dose-response relationships are common. This analytical refinement, combined with trajectory analysis, strengthens the case that the six markers capture a graded, escalating risk process rather than an arbitrary statistical association.

Importantly, the outcome measure was not a loose laboratory surrogate. The investigators used clinically adjudicated cardiogenic shock, meaning each case was reviewed and confirmed against clinical criteria rather than inferred from billing codes or a single measurement. That adjudication process lends the 18.5 percent incidence figure and the mortality association greater credibility than many earlier reports, which have varied widely in how they defined shock in SFTS. The retrospective design and the waiver of informed consent, approved by the hospital’s ethics committee under the Declaration of Helsinki, were appropriate for the anonymized data involved.

The authors are careful to note the limits of their work before it can change practice. As a single-center retrospective study, the findings require external validation in other hospitals and regions, and the authors themselves acknowledge that more objective cardiac assessment, such as direct hemodynamic measurement or echocardiographic evaluation of pump function, would strengthen future iterations of the risk model. The six-biomarker panel is best understood today as an early-warning framework, a way to flag patients whose inflammatory, cardiac, renal, coagulation, and lipid profiles are moving in the wrong direction, rather than as a finished diagnostic tool ready for routine deployment.

Even so, the study arrives at a moment of growing concern about SFTS. The disease, caused by a phlebovirus in the family Phenuiviridae, continues to expand its geographic footprint in China, South Korea, Japan, and Vietnam, and case fatality rates in severe cohorts have ranged into the double digits. No licensed specific antiviral therapy exists, so management remains supportive, which makes early identification of patients at imminent risk of shock one of the few levers clinicians can currently pull. A biomarker panel that can be measured on standard hospital laboratories, combined with the knowledge that 85 percent of shock events arrive within seven days of admission, gives intensive care teams a concrete, actionable window. The work was supported by a Chinese provincial health research project focused on SFTS intensive care and immune precision intervention under a medical-prevention collaboration framework, and the open-access publication ensures the findings are immediately available to clinicians across the affected region. If validated externally, this multisystem biomarker approach could shift SFTS care from reactive management of established shock toward anticipatory protection of the heart during the vulnerable first week of illness.

Subject of Research: Biomarker trajectories and early prediction of cardiogenic shock in severe fever with thrombocytopenia syndrome

Article Title: Multisystem biomarker trajectories and early risk of clinically adjudicated cardiogenic shock in severe fever with thrombocytopenia syndrome

Article References: Multisystem biomarker trajectories and early risk of clinically adjudicated cardiogenic shock in severe fever with thrombocytopenia syndrome. (n.d.). https://doi.org/10.1186/s12879-026-14600-z

Image Credits: AI Generated

DOI: 10.1186/s12879-026-14600-z

Keywords: SFTS, cardiogenic shock, biomarkers, interleukin-6, natriuretic peptide, cytokine storm, viral hemorrhagic fever, risk prediction, coagulation, mortality, Nanjing Second Hospital, Cox regression