Biomarkers of Disease: Discovery and Clinical Applications

The cGAS-STING pathway initiates the core cascade of innate immune defense by recognizing pathogen-associated and self-derived abnormal nucleic acids, and key molecules (such as cGAS, STING, downstream IFN-β, IL-6, etc.) may serve as biomarkers in various diseases. The diverse mechanisms by which distinct nucleic acids activate this pathway provide novel insights for therapeutic strategies targeting infectious diseases, cancer, and autoimmune disorders. To prevent aberrant cGAS-STING pathway activation, cells employ multiple regulatory mechanisms, including restricting self-DNA recognition and terminating downstream signaling. Strategies to mitigate pathological activation involve reducing nucleic acid accumulation through nuclease degradation (e.g., of mitochondrial DNA or neutrophil extracellular traps, NETs) or directly inhibiting cGAS or STING. This review elucidates the molecular mechanism of nucleic acid-mediated regulation of cGAS-STING and its role in disease regulation. Full article

Elevated human epididymis protein 4 (HE4) levels decreased in patients with CF (pwCF) in response to CFTR-specific drugs and negatively correlated with FEV1% predicted values (ppFEV1). Objectives: Although elexacaftor/tezacaftor/ivacaftor (ETI, Kaftrio^®) demonstrates more substantial effectiveness than lumacaftor/ivacaftor (LUM/IVA, Orkambi^®) in pwCF, plasma biomarkers have not been used to compare treatment efficacy. Hence, our aim was to correlate the change in HE4 levels and the clinical effects of these CFTR modulators (CFTRm). Methods: Serum HE4 concentrations were measured in a total of 123 pwCF homozygous for the p.Phe508del-CFTR variant before treatment and 1–6 months after either ETI or LUM/IVA administration. A correlation between serum HE4 and ppFEV1 was assessed using the Spearman test. HE4 protein levels were also analyzed in the supernatants of p.Phe508del-CFTR CFBE 41o- cells before and after treatment with these CFTRm, and their direct effect on CFTR function was monitored by the whole-cell patch-clamp technique. Results: Serum HE4 levels were reduced below baseline after 3 months of either ETI or LUM/IVA (mean delta HE4: −38.5 vs. −18.5 pmol/L, respectively) when the mean change of ppFEV1 was 13.6 vs. 1.6% and remained decreased up to 6 months. A significant inverse correlation between HE4 and ppFEV1 was observed in both study cohorts (r = −0.537 and r = −0.575, respectively; p < 0.0001). In agreement with ex vivo results, the effect on p.Phe508del-CFTR was more pronounced by ETI than LUM/IVA in CFBE cells, showing a larger improvement in p.Phe508del-CFTR function and reductions in HE4 levels at 24 h. Conclusions: Serum HE4 negatively correlates with lung function improvement and monitors better drug efficacy in pwCF under ETI than LUM/IVA. Full article

Background/Objectives: Intrinsic biomarkers, such as serum vitamin D levels and the conjunctival ultraviolet autofluorescence (CUVAF) area, have been proposed to quantify sunlight exposure. Evidence suggests that reduced outdoor activity during the SARS-CoV-2 pandemic accelerated the progression of myopia; however, there is little information on the impact of such restrictions on vitamin D levels and CUVAF area in populations with myopia. This study aims to assess the association between serum vitamin D levels and conjunctival ultraviolet autofluorescence area (CUVAF) in young adults with myopia during and after the pandemic, as well as its relationship with sun exposure habits and the use of skin protection measures. Methods: A prospective observational study was carried out. A total of 59 students participated, 32 with a diagnosis of myopia and 27 controls, during SARS-CoV-2 pandemic. Two serological tests for total 25-hydroxy vitamin D (D2 + D3) (Calciferol) were taken, activity habits and sun exposure were identified using the Intermountain Live Well Institute tool, and CUVAF images were taken post-pandemic. Results: In the 59 participants, we observed similar vitamin D concentrations between the myopic and control groups during and after the pandemic. However, analysis of CUVAF areas after the pandemic revealed that myopes had significantly smaller areas compared to controls (p < 0.05). Conclusions: The study demonstrated that using vitamin D as a biomarker for outdoor activity requires additional investigation; the CUVAF biomarker showed a significant association with myopia. Full article

Background/Objectives: Borderline personality disorder (BPD) is a psychiatric disorder characterized by emotional instability, impulsive behavior, and impaired interpersonal relationships. It is associated with a high prevalence of childhood trauma and neurobiological changes. This study aimed to compare ophthalmologic parameters, namely, optic nerve sheath diameter, intraocular pressure, and dry eye, in patients with BPD with healthy controls and to investigate the relations between these parameters and childhood trauma. Methods: This study included 51 female patients with BPD between the ages of 18 and 35 years, who were not using psychotropic medication, and 51 healthy controls matched for age and educational level. Optic nerve sheath diameter, intraocular pressure, and tear break-up time were measured, and trauma history was evaluated using the Childhood Trauma Questionnaire-Short Form. Independent t-test and Pearson correlation analysis were used in statistical analyses. Results: Patients with BPD were found to have significantly higher mean optic nerve sheath diameter scores (left: 3.94 ± 0.43, right: 3.97 ± 0.47) compared with healthy controls (left: 3.76 ± 0.44, right: 3.78 ± 0.45) (p < 0.05). The groups showed no significant difference in intraocular pressure and dry eye parameters (p > 0.05). A significant positive correlation was noted between emotional abuse scores and the optic nerve sheath diameter of the left eye in patients with BPD (p < 0.05; r = 0.364). Conclusions: An increased optic nerve sheath diameter may be a potential peripheral biomarker reflecting chronic stress or changes in intracranial physiology in patients with BPD. This increase is particularly associated with a history of emotional abuse. Ophthalmological parameters may contribute to understanding the neurobiological basis of BPD and serve as peripheral biomarkers or indicators of neurobiological changes. Full article

Background: Septic arthritis is an orthopedic emergency. However, optimal biomarkers and diagnostic criteria remain unclear. The study aimed to evaluate the diagnostic performance of routinely used and novel biomarkers, including serum C-reactive protein (CRP), synovial white blood cells (WBC), pentraxin-3 (PTX3), interleukin-6 (IL-6), and presepsin, in distinguishing septic from non-septic arthritis. Methods: Thirty-one patients undergoing arthrocentesis were included. Patients were categorized into septic and non-septic arthritis groups. Synovial fluid and serum samples were analyzed for five biomarkers. Diagnostic performance was assessed by calculating the area under the curve (AUC), accuracy, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV). Results: Synovial WBC demonstrated the highest diagnostic performance among single biomarkers (AUC = 0.837, p = 0.012). Among novel biomarkers, PTX3 showed the highest accuracy and sensitivity. The serum CRP and synovial WBC combination yielded an AUC of 0.853, with 100% sensitivity, 68.0% specificity, 42.9% PPV, and 100% NPV. Adding all three novel biomarkers to this combination increased the AUC to 0.887 (p = 0.004), maintaining 100% sensitivity and NPV. When individually added, PTX3 achieved 100% sensitivity and NPV, while presepsin showed the highest specificity (96.0%), PPV (75.0%), and accuracy (87.1%). Conclusions: Serum CRP and synovial WBC remain essential biomarkers for diagnosing septic arthritis; however, combining them with PTX3, IL-6, and presepsin improved diagnostic accuracy. PTX3 is best suited for ruling out septic arthritis due to its high sensitivity and NPV, whereas presepsin is more useful for confirmation, given its specificity and PPV. These results support a tailored biomarker approach aligned with diagnostic intent. Full article

Background/objectives: Polycystic ovary syndrome (PCOS) and metabolic dysfunction-associated steatotic liver disease (MASLD) are common co-morbidities in women of reproductive age. PCOS is highly heterogeneous and is, therefore, divided into four phenotypes. MASLD leads to numerous systemic complications. Studies to date have shown an association between PCOS and MASLD. This study was designed to compare the FIB-4 score (based on age, alanine aminotransferase, aspartate aminotransferase and platelet count) and the results of shear wave elastography in assessing the risk of developing MASLD by patients with PCOS divided by phenotypes. Methods: The study enrolled 242 women age 18–35 years with PCOS diagnosed according to Rotterdam criteria, hospitalized at the Department of Gynaecological Endocrinology of the University Clinical Centre in Katowice. The study subjects were assigned to phenotypes A to D. Clinical and biochemical assessments were performed (including androgens and metabolic parameters), and the FIB-4 index was calculated. Liver fibrosis was evaluated by shear wave elastography. To balance the group sizes of phenotypes, oversampling with replacement was applied (PROC SURVEYSELECT, SAS), increasing the number of observations for phenotypes B, C, and D fivefold. Statistical analyses were performed based on data distribution (Shapiro–Wilk test), using ANOVA or the Kruskal–Wallis test with Dunn’s correction. Statistical significance was set at p < 0.05. Results: The FIB-4 score was the highest in phenotype B patients (0.50 ± 0.15), and the lowest in phenotypes A and C (0.42 ± 0.14). The highest rate of positive elastography findings was recorded in phenotype A patients (34.7%) and the lowest in phenotype C group (13.5%). Significant differences between the phenotypes were also found in terms of androgen levels, insulin, HOMA-IR, and the lipid profile. Among patients with positive elastography, the highest FIB-4 scores were recorded in phenotype C group (0.44 ± 0.06), but the differences between the phenotypes were not statistically significant. Conclusions: The FIB-4 score was the highest in phenotype B patients and differed significantly from phenotypes A, C and D. In the elastography exam, the fibrosis index was statistically significantly higher in phenotype A compared to other phenotypes. No correlation was detected between the FIB-4 index and positive elastography. The findings suggest that the FIB-4 index may be used for MASLD screening, but its usefulness as a predictor of eligibility for elastography requires more research. Full article

Background/Objectives: Frailty is a key determinant of outcomes in older adults with heart failure (HF). The free triiodothyronine/free thyroxine (FT₃/FT₄) ratio has emerged as a promising frailty biomarker that reflects metabolic and systemic resilience. This study investigates its association with frailty, nutrition, muscle strength, inflammation, and one-year mortality in very old patients with HF. Methods: In this longitudinal, single-center study, we enrolled 193 older outpatients (mean age, 86.5 ± 6.1 years; 56% women) recently discharged after acute HF. All patients underwent physical examination, blood testing, and comprehensive geriatric assessment, including handgrip strength (HGS). Participants were stratified by FT₃/FT₄ ratio (<1.7 vs. ≥1.7). Associations with the Clinical Frailty Scale (CFS) were examined using multivariable linear regression. Spearman’s correlations assessed relationships with inflammatory and nutritional biomarkers. Cox regression evaluated the association with all-cause mortality. Results: Patients with a low FT₃/FT₄ ratio (31.1%) exhibited greater frailty (CFS: median [IQR], 6 [2] vs. 4 [3]; p = 0.020), poorer nutritional status (Mini Nutritional Assessment: 10 [4] vs. 12 [3]; p = 0.008), and lower HGS (mean ± SD, 16.8 ± 3.7 kg vs. 20.3 ± 4.8 kg; p = 0.002). An inverse association was identified between the FT₃/FT₄ ratio and frailty (adjusted β = −0.09; p = 0.019). Individuals with low FT₃/FT₄ also showed elevated inflammatory markers and had more than double the one-year mortality rate compared to those with higher ratios [HR 2.32 (95% CI, 1.24–4.34; p = 0.007)]. Conclusions: In very old adults recently hospitalized for HF, a lower FT₃/FT₄ ratio was associated with frailty, malnutrition, inflammation, and increased mortality, supporting its potential role as a marker of biological vulnerability. Full article

Background/Objective: Neurofilament light chain (Nf-L), neurofilament heavy chain (Nf-H), and chitinase 3-like 1 (CHI3L1) are cerebrospinal fluid (CSF) biomarkers of neuroaxonal damage and inflammation in multiple sclerosis (MS). Their longitudinal response to disease-modifying therapies and association with clinical and radiological outcomes remain incompletely understood. The aim of this study is to evaluate the impact of interferon beta (IFN-β) therapy on CSF levels of Nf-L, Nf-H, and CHI3L1 in early relapsing–remitting MS (RRMS) and assess their association with long-term clinical outcomes and MRI activity. Methods: We conducted a prospective two-year observational study involving 14 treatment-naive RRMS patients who initiated IFN-β therapy. CSF levels of Nf-L, Nf-H, and CHI3L1 were measured at baseline and after two years. Clinical disability was assessed via the Expanded Disability Status Scale (EDSS) and by studying brain MRI activity. A 15-year clinical follow-up was performed for 12 patients. Results: Nf-L levels significantly decreased after two years of IFN-β treatment (p = 0.039), while CHI3L1 levels significantly increased (p = 0.001). Nf-H levels remained stable. Nf-L and CHI3L1 levels at baseline and follow-up correlated with relapse rate and long-term EDSS. Nf-H levels correlated with EDSS scores but not with relapse or MRI activity. A trend toward a positive correlation between increasing Nf-L levels and MRI activity was observed (p = 0.07). Conclusions: CSF biomarkers demonstrate differential responses to IFN-β therapy in early RRMS. Nf-L emerges as a sensitive biomarker of treatment response and disease activity, while CHI3L1 may reflect ongoing tissue remodeling and inflammation. These findings support the utility of CSF biomarker monitoring for personalized treatment strategies in MS. Full article