The prevalence of VTE is unexpectedly high (46.8%) in hospitalized patients with SCAP in high-altitude regions and may be associated with a poor prognosis, and a new prediction model including PaO2/FiO2 ratios, D-dimer levels, and bedridden times showed better performance than standard scores in identifying at-risk patients.
Key Findings
Results
VTE occurred in 46.8% of patients with severe community-acquired pneumonia (SCAP) admitted to a high-altitude hospital.
74 of 158 prospectively enrolled adult patients developed VTE.
68 patients had deep vein thrombosis (DVT), 21 had pulmonary embolism (PE), and 15 had both DVT and PE.
Patients were admitted to Lhasa People's Hospital (a high-altitude facility) between January 1, 2023, and December 31, 2024.
VTE prophylaxis was administered to 77.8% of patients but did not significantly reduce VTE incidence.
123 of 158 patients (77.8%) received VTE prophylaxis.
There was no significant difference in VTE incidence among groups with different prophylactic measures (p = 0.838).
This finding suggests that standard prophylactic strategies may be insufficient in this high-altitude, high-risk population.
Results
Lower PaO2/FiO2 ratio was independently associated with VTE occurrence in SCAP patients at high altitude.
PaO2/FiO2 ratios ≤ 160 mmHg were associated with VTE (OR = 2.354, 95% CI 1.025–5.406, p = 0.044) on multivariate logistic regression.
This threshold reflects severe hypoxemia and is consistent with the hypothesis that high-altitude hypoxia promotes a hypercoagulable state.
Results
Elevated D-dimer levels (≥ 3.0 μg/mL) were independently associated with VTE in SCAP patients at high altitude.
D-dimer levels ≥ 3.0 μg/mL were associated with VTE (OR = 2.901, 95% CI 1.329–6.334, p = 0.008) on multivariate logistic regression.
D-dimer is a marker of fibrin degradation and reflects active thrombosis or coagulation activity.
Results
Longer bedridden time (≥ 3 days) was independently associated with VTE occurrence.
Bedridden time ≥ 3 days was associated with VTE (OR = 3.540, 95% CI 1.494–8.391, p = 0.004) on multivariate logistic regression.
This was the strongest independent predictor among the three identified risk factors based on odds ratio magnitude.
Results
A new prediction nomogram model combining PaO2/FiO2 ratio, D-dimer levels, and bedridden time outperformed standard VTE risk scores for SCAP patients at high altitude.
The new model achieved an AUC of 0.886 (95% CI 0.826–0.931), with sensitivity of 74.3% and specificity of 89.3%.
The Padua prediction score achieved an AUC of 0.624, and the Caprini prediction score achieved an AUC of 0.622.
The new model's superiority over both standard scores was statistically significant (all p < 0.05).
The calibration curve of the nomogram model showed good predictive value.
Results
Patients with VTE had significantly lower 30-day cumulative survival rates than patients without VTE.
The 30-day cumulative survival rate of patients with VTE was significantly lower than that of patients without VTE (p = 0.034).
This finding indicates that VTE occurrence in this population is associated with poor prognosis.
What This Means
This research suggests that blood clots — specifically a condition called venous thromboembolism (VTE), which includes both deep vein thrombosis (DVT) and pulmonary embolism (PE) — are strikingly common among patients hospitalized with severe pneumonia in high-altitude regions. In this study conducted at a hospital in Lhasa, Tibet, nearly half of all severe pneumonia patients (46.8%) developed VTE during their hospital stay. This rate is notably higher than what is typically reported in similar patients at lower altitudes, supporting the idea that the reduced oxygen levels at high altitude may make the blood more prone to clotting.
The study identified three key warning signs that were independently linked to a higher likelihood of developing VTE: very low blood oxygen levels (measured by the PaO2/FiO2 ratio), high levels of a clotting marker in the blood called D-dimer (≥ 3.0 μg/mL), and being confined to bed for three or more days. Using these three factors together, the researchers built a new prediction tool (a nomogram) that was much better at identifying high-risk patients than two widely used standard scoring systems (the Padua and Caprini scores). Despite most patients receiving standard blood clot prevention treatments, these measures did not appear to significantly reduce VTE rates, suggesting that current approaches may need to be rethought for this population. Patients who developed VTE also had significantly worse survival at 30 days, highlighting the serious consequences of clot formation in this setting.
This research suggests that patients with severe pneumonia in high-altitude areas face a uniquely elevated risk of potentially life-threatening blood clots, and that the standard tools used to predict clot risk may not be adequate for this population. The new prediction model developed in this study could help clinicians identify the most vulnerable patients earlier. The findings also raise important questions about whether more aggressive or tailored preventive strategies — beyond current standard care — are needed for severe pneumonia patients in high-altitude environments.
Zhang Y, Zhang Y, Xiao B, Lu M, Jia J, Shi X, et al.. (2026). Venous Thromboembolism in Severe Community-Acquired Pneumonia at High-Altitude Areas: Prevalence, Risk and Outcome.. The clinical respiratory journal. https://doi.org/10.1111/crj.70230