Is Stroke-Associated Pneumonia Related to Transthyretin Levels?

Low transthyretin levels at hospital admission have been independently correlated with stroke-associated pneumonia (SAP). A single-center, retrospective study was conducted between 2015 and 2020 at the First Affiliated Hospital of Wenzhou Medical University, in Wenzhou, Zhejiang, China. Results of the analysis were published in the journal Nutrition, Metabolism & Cardiovascular Diseases.

The investigators sought to explore the potential relationship between levels of the

55-kDa protein transthyretin and the development of SAP among patients following ischemic stroke. Inclusion criteria were age of 18 to 80 years and acute cerebral ischemia within 7 days of stroke onset, which was confirmed by cranial magnetic resonance imaging or computed tomography (CT) within 24 hours following hospitalization.

A total of 920 individuals were enrolled in the current study. Stroke-associated pneumonia was diagnosed when lower respiratory tract infections developed during the initial 7 days after experiencing a stroke, based on modified US Centers for Disease Control and Prevention (CDC) criteria for hospital-acquired pneumonia. In the current study, both definite and probably SAP, defined according to modified CDC criteria, were considered to be SAP, excluding the burden of chest x-ray or CT scan findings. All patients with pneumonia prior to the onset of stroke, as well as community-acquired pneumonia, were excluded from the study.

Overall, SAP was diagnosed in 13.4% (123 of 920) of the study population, of whom 77 were men and 46 were women. Per multivariable analysis, serum transthyretin levels were significantly lower in patients with SAP compared with those without the infection (231 ± 80 vs 279 ± 75, respectively; P <.001), following adjustment for confounders. When compared with those in the non-SAP group, individuals in the SAP group were older and had a higher percentage of diabetes, hypertension, hyperlipidemia, cardioembolism, atrial fibrillation, and thrombolysis.

Low transthyretin levels (ie, ≤252 mg/L) were independently associated with the development of SAP (odds ratio, 3.370; 95% CI, 1.763-6.441; P <.001). Further, individuals with SAP experienced worse clinical outcomes compared with those without SAP at hospital discharge. Leukocyte counts, neutrophil-to-lymphocyte ratio (NLR), and dysphagia were all shown to be linked to the development of SAP. Those in the SAP arm had higher National Institutes of Health Stroke Scale (NIHSS) scores at baseline,  high sensitivity CRP or C reactive protein (hs CRP) levels, and A2DS2 scores (score to predict ischemic stroke based on age, atrial fibrillation, dysphagia, sex, and stroke severity).

Transthyretin levels were positively correlated with lymphocyte counts and hemoglobin levels (P <.05 for both); they were negatively correlated with age, hs-CRP levels, fasting blood glucose levels, neutrophil counts, NLR, A2DS2 score, and NIHSS score (P <.05 for all).

The researchers concluded that current study findings might help shape further clinical investigations into the value of nutritional supplementation in preventing SAP, given that prior studies have shown enteral nutrition can increase transthyretin levels and reduce infectious complications and gastrointestinal motility disorders in patients with stroke.

Reference

Qiu H, Song J, Hu J, et al. Low serum transthyretin levels predict stroke-associated pneumonia.  Nutr Metab Cardiovasc Dis. Published online December 9, 2021. doi:10.1016/j.numecd.2021.12.008