CBC-Derived Inflammation Signals Track With Ascending Aortic Enlargement
Routine blood count markers that are usually ordered for entirely different reasons may help flag which dilated ascending aortas are more likely to enlarge during surveillance. In a retrospective single-center cohort spanning 2000 to 2023, red cell distribution width stood out as the only marker independently associated with overall aortic growth across the full population, while neutrophil-to-lymphocyte ratio and systemic immune-inflammation index fell short of significance in the broader analysis.
The biologic logic is familiar even if the clinical application is still tentative. Aortic enlargement is not just a passive stretching problem driven by pressure and geometry; inflammatory signaling can reshape the vessel wall, weaken extracellular matrix support, and accelerate remodeling long before a dissection threshold is crossed. In that setting, simple hematologic indices may function as rough readouts of systemic inflammatory tone rather than as disease-specific biomarkers.
The cohort included adults who had two CT scans of the native ascending aorta at least six months apart, with patients carrying aortitis or lacking complete blood counts during follow-up excluded. Growth was defined conservatively as a 2-mm increase in mid-ascending aortic diameter. Investigators adjusted for age, sex, body mass index, baseline diameter, systolic blood pressure, diabetes, and heritable thoracic aortic disease, which keeps the analysis anchored to major clinical confounders that also shape aneurysm behavior.
A single sentence captures the central result: RDW moved with growth when the entire cohort was examined, while NLR and SII did not.
Dilated Aortas Showed the Strongest Signal
The overall population was large, but laboratory availability narrowed the analytic samples: 1,882 patients had data for RDW, 1,471 for NLR, and 1,468 for SII. Across the full cohort, 192 patients, or 10.2%, met the growth definition. At the patient level, RDW carried an odds ratio of 1.071, with a 95% CI of 1.002 to 1.144 and a p value of 0.043. The interval-level model produced a similar association, with an odds ratio of 1.075, 95% CI 1.012 to 1.141, and p=0.019. NLR trended but did not reach statistical significance in the overall cohort, and SII was farther from the threshold.
The story changed once baseline aortic size entered the frame. Among patients with guideline-defined ascending aortic dilation, set at 40 mm, all three markers were associated with interval growth. RDW showed an odds ratio of 1.14, NLR 1.05, and SII 1.01 per 100 units; all were significant at p=0.014. In contrast, none of the markers tracked with growth in aortas smaller than 40 mm, and the interaction signal was significant for NLR at p=0.01.
That pattern matters because a dilated aorta may be the stage at which inflammatory burden becomes more biologically consequential. Once the wall is already remodeled and mechanically stressed, small increments in systemic inflammation may be enough to tilt the balance toward further expansion. In smaller aortas, the same blood count signals may be too nonspecific, too weak, or simply disconnected from the tissue-level processes that govern enlargement.
The practical consequence is narrow but real: an elevated inflammatory index from a routine CBC should not be read as a stand-alone predictor of impending danger, but it may add context when aortic diameter is already enlarged and imaging follow-up is being planned.
Why RDW May Carry More Information Than Expected
RDW is not an inflammatory marker in the narrow laboratory sense, yet it often rises in settings linked to chronic disease burden, oxidative stress, nutritional disturbance, and altered erythropoiesis. Those processes can travel with systemic inflammation and vascular injury. In aortic disease, where extracellular matrix turnover, smooth muscle cell dysfunction, and inflammatory infiltration all contribute to remodeling, RDW may be reflecting a broader physiologic instability rather than a single causal pathway.
NLR and SII are more explicitly tied to white blood cell balance and platelet-neutrophil interactions, so their partial signal in the dilated subgroup is biologically plausible. Even so, the fact that they did not hold up across the entire cohort suggests a ceiling on how much information routine CBC-derived indices can provide. These measures are attractive because they are cheap, available, and already embedded in everyday care, but they remain surrogate markers, not direct windows into the aortic wall.
The study design also invites caution. It was retrospective, drawn from a single center, and dependent on available imaging and laboratory data. Growth was defined by a 2-mm diameter change, which is clinically meaningful in surveillance practice but still vulnerable to measurement variability across scans. The authors adjusted for several key covariates, yet residual confounding is always possible when inflammatory markers are used as proxies for a complex vascular disease process.
What the Preprint Can and Cannot Support
This preprint does not justify changing surveillance thresholds or treatment decisions. It does, however, strengthen the argument that ascending aortic disease is not governed by diameter alone. The classic paradigm of waiting for a size cutoff misses the biologic heterogeneity of aneurysm progression, and the present findings fit with the idea that inflammatory activity may help separate stable dilation from more active enlargement.
The most defensible clinical reading is restrained: in patients with an already dilated ascending aorta, CBC-derived inflammatory markers may eventually help refine risk stratification alongside diameter, blood pressure, and genetic context. In patients with a normal-sized aorta, the same indices appear less informative for short-term growth in this dataset. Prospective work will need to determine whether these signals hold when repeated measurements, standardized imaging protocols, and more specific inflammatory assays are used.
Data availability was limited to request from the corresponding author, and the manuscript remains a preprint without peer review. Even so, the direction of effect is coherent with vascular biology. Inflammation can drive wall remodeling without waiting for dramatic clinical events, and routine laboratory values may be picking up a faint version of that process long before the aorta reaches a surgical threshold.