Logo: to the web site of Uppsala University

BACKGROUND: Cardiovascular disease (CVD) remains the leading cause of mortality worldwide. Lipid biomarkers, including direct low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), apolipoprotein B (ApoB), and apolipoprotein A1 (ApoA1), are essential tools for cardiovascular risk assessment. Monitoring patient-derived median values over time may provide insights into population health and analytical performance. This study provides a descriptive analysis of population-level lipid results spanning nearly two decades. While trends in patient medians may support quality assurance, these data do not constitute a validated approach to risk prediction or definitive analytical monitoring due to the absence of outcome and treatment information.

METHODS: We retrospectively analyzed routine clinical laboratory data from Uppsala University Hospital, Sweden, covering January 2006-December 2024. A total of 890,948 LDL-C, 867,446 HDL-C, 64,787 ApoB, and 65,500 ApoA1 results were included. Measurements were performed on Abbott Architect systems until 2021, after which assays were transferred to Roche Cobas Pro platforms. Statistical analyses included trend evaluation, variability assessment, and seasonal pattern analysis.

RESULTS: Women had modestly higher LDL-C and HDL-C levels compared to men, while ApoB values were similar between sexes. ApoA1 was notably higher in women. Over the 19-year period, median LDL-C declined from 3.18 to 2.62 mmol/L, consistent with improved lipid management. HDL-C remained stable (1.36-1.45 mmol/L), while ApoB and ApoA1 concentrations showed minimal change. Variability was highest for LDL-C (median CV 6.4%) and lowest for ApoA1 (median CV 2.6%). Seasonal variation was negligible across all analytes. Testing volumes increased substantially for LDL-C and HDL-C, whereas ApoB and ApoA1 requests peaked around 2010 and later declined.

CONCLUSIONS: Long-term monitoring of median patient values demonstrates declining LDL-C, stable HDL-C, and consistent ApoB/ApoA1 ratios with minimal seasonal effects. These findings highlight the potential utility of patient medians as supplementary quality indicators and for population-level lipid surveillance.

In response to Campbell and Cappuccio's comments, this letter clarifies and defends the appropriate use of spot-urine sodium estimates in population-level and exploratory analyses. The critique misrepresents key aspects of the study design and overstates the limitations of spot-urine equations. While acknowledging that these methods are unsuitable for precise individual assessment, they perform adequately for ranking individuals and examining population-level associations, as supported by extensive validation studies. The reported associations with metabolic traits were internally consistent, biologically plausible, and in agreement with findings from studies using 24-hour urine collections. Dismissing such analyses as "invalid" undermines constructive scientific dialogue and disregards the exploratory value of transparent, hypothesis-generating research.

Background: Biomarkers reflecting neuroplasticity, inflammation, and vascular integrity may explain variability in post-stroke recovery. This exploratory substudy of the PRACTISE trial (NCT05355831) examined longitudinal biomarker changes during stroke rehabilitation and their associations with upper-extremity (UE) motor recovery.

Methods: A total of 24 patients with subacute ischemic stroke (21 completers) received patient-tailored transcranial direct current stimulation (TDCS) or sham during four weeks of UE rehabilitation. UE motor function (FMA-UE) and clinical outcomes - including cognition (MoCA), depression (BDI-II), and quality of life (EQ-5D-5L) - were assessed at baseline, end-of-treatment, and at 12-weeks along with the biomarkers plasma Cathepsin-B, Cathepsin-S, E-selectin, and high-sensitivity C-reactive protein (hsCRP). Baseline MRI was rated for small-vessel-disease (SVD) burden using STRIVE criteria. Longitudinal biomarker changes were evaluated using mixed-effects regression.

Results: Despite substantial interindividual variability, increases in hsCRP were associated with less FMA-UE improvement from baseline to end-of-treatment (β = -0.75 ± 0.26, p = 0.01). The remaining biomarkers were not significantly associated to FMA-UE improvement. Four participants who later experienced major adverse cardiovascular events showed high levels of hsCRP and Cathepsin-S at baseline. Sensitivity analyses revealed no significant associations with changes in cognition, depression, or quality-of-life, although a trend-level positive association was observed between E-selectin and MoCA-score.

Conclusion: Inflammatory activation-particularly increased hsCRP and Cathepsin-S levels-was associated with reduced motor recovery and characterized individuals who subsequently had major adverse cardiovascular events. These findings support further investigation of inflammatory biomarkers as indicators of both recovery potential and vascular risk during subacute stroke rehabilitation.

Background

Calprotectin, a neutrophil activation marker, is a promising diagnostic biomarker for infection and sepsis, but its usefulness in the emergency department (ED) is unclear. The aim of this study was to investigate the diagnostic value of calprotectin for sepsis and the source of infection in the ED.

Methods

A total of 583 prospectively included patients presenting with suspected sepsis to the ED of a university hospital in southern Sweden were analyzed. Calprotectin was measured in plasma samples obtained at admission.

Results

Mean age was 69 years and 49% were female. Calprotectin discriminated between sepsis and noninfectious systemic inflammatory response syndrome with an area under the curve (AUC) of 0.63, but was not an independent predictor in multivariable analysis including C-reactive protein (CRP). The Modified Early Warning Score did not show any discriminatory ability. Calprotectin and CRP discriminated between lower respiratory tract infection and (1) upper respiratory tract infection, (2) urinary tract infection, and (3) other sources of infection. Addition of calprotectin to CRP significantly increased the AUC for lower versus upper respiratory tract infection and lower respiratory tract infection versus urinary tract infection. Calprotectin was an independent predictor for all outcomes while CRP was only an independent predictor of lower versus upper respiratory tract infection.

Conclusions

Calprotectin may improve differentiation of lower respiratory tract infections from upper respiratory tract infections and urinary tract infections in patients presenting to the ED with sepsis. Further research is needed to clarify if calprotectin adds diagnostic value to standard clinical assessment.

Advances in ultrasensitive immunoassays have enabled reliable quantification of neuroglial biomarkers in blood, providing valuable insights into neurological disorders. However, cross-platform evaluations are necessary to ensure comparability and standardization. This study aimed to compare the analytical performance of a Single Molecule Array (Simoa) and an ultrasensitive electrochemiluminescence (ECL) assay for quantifying neurofilament light chain (NfL) and glial fibrillary acidic protein (GFAP) in human serum. Baseline serum samples from 174 participants in the RIFUND trial were analyzed in parallel on both platforms. Concentrations of NfL and GFAP were compared using Spearman correlation, Bland–Altman analyses, reproducibility assessments, dilution linearity, and cross-platform recovery. All samples were quantifiable on both platforms. NfL concentrations correlated strongly between methods (Spearman correlation r = 0.88, p < 0.0001), whereas GFAP correlated moderately (r = 0.77, p < 0.0001). Inter- and intra-assay coefficients of variation were comparable between platforms for both analytes. The relationship between the two assays could be described with the following equations: NfLECL = 7.63 × NfLSIMOA + 1.71 and GFAPECL = 0.332 × GFAPSIMOA + 4.22. Dilution linearity was excellent on both platforms (R2 > 0.99), although cross-platform recovery varied systematically across the analytical range. Both Simoa and ECL demonstrated strong analytical performance for neuroglial biomarker quantification in serum. Despite systematic differences in absolute concentrations, relative agreement was high, particularly for NfL. These findings highlight the need for platform harmonization and provide empirically derived conversion factors to support analytical comparability in research and clinical applications.

UNLABELLED: Accurate evaluation of kidney function is vital in the pediatric intensive care unit (PICU), where even small changes in cystatin C and creatinine concentrations can affect clinical decision-making. Diurnal patterns in renal biomarkers have been reported in adults, but their relevance in critically ill children remains unclear. Understanding whether sampling time contributes to biological variability is essential for reliable interpretation of kidney function tests. This retrospective study included 8619 cystatin C and 9314 creatinine results collected in a tertiary PICU between April 2014 and September 2025. The hourly distribution of sampling and hourly biomarker percentiles (0.10, 0.25, and 0.50) were evaluated across the 24-h cycle. Diurnal variation was quantified using coefficients of variation (CVs). Sampling was strongly clustered in the early morning, with 38.6% of cystatin C and 37.4% of creatinine samples drawn at 5:00-5:59 AM. The 0.10-0.50 percentiles of cystatin C showed minimal diurnal variation (CV 4.5-6.3%). Creatinine exhibited slightly greater variability, with CVs of 7.4-11.6% across the same percentiles. Median creatinine was significantly higher in the afternoon/evening than in the early morning, while cystatin C showed no clinically relevant hourly fluctuations.

CONCLUSION: In critically ill children, cystatin C demonstrates limited diurnal variation, while creatinine shows modest but measurable fluctuations across the 24-h period. These findings suggest that cystatin C is relatively robust to sampling time in the PICU, whereas creatinine may vary enough to influence interpretation in borderline cases. Incorporating knowledge of sampling time may improve the accuracy of kidney function assessment and AKI classification in pediatric critical care.

WHAT IS KNOWN: • Creatinine and cystatin C can show biological and circadian variability in adults and older children, with creatinine generally exhibiting greater within-day fluctuation than cystatin C.

WHAT IS NEW: • In critically ill children, cystatin C shows minimal diurnal variation, whereas creatinine displays modest but measurable time-of-day-related increases, indicating that sampling time may influence creatinine interpretation but not cystatin C in the PICU setting.

Background: Tacrolimus is a key immunosuppressive drug used to prevent organ rejection after transplantation. Its narrow therapeutic window and high interindividual pharmacokinetic variability make therapeutic drug monitoring (TDM) essential. This study aimed to (1) characterize long-term trends in tacrolimus concentrations; (2) assess potential seasonal variation; and (3) evaluate the suitability of patient medians as a tool for laboratory quality monitoring. Methods: A retrospective analysis was conducted on 113,735 tacrolimus whole-blood results obtained between 2006 and 2024 at Uppsala University Hospital, Sweden. Samples were analyzed using immunoassays on the Hitachi 912 (Microgenics) until 2008, the Abbott Architect until 2021, and the Roche Cobas Pro e 801 thereafter. Annual patient medians and percentiles (10th, 25th, 50th, 75th, and 90th) were calculated. Seasonal variation was assessed by comparing monthly test volumes and concentration distributions. Results: The annual number of tacrolimus results increased from 5616 in 2006 to 7320 in 2024, comprising 67,133 male and 46,602 female patient results. All distribution metrics declined steadily over the study period, with median tacrolimus concentrations decreasing by 20–30%. The July test volume was approximately 15% lower than in other months, but no meaningful seasonal variation in tacrolimus concentrations was observed; monthly medians and percentiles remained stable throughout the year. Conclusions: Tacrolimus concentrations at the population level have decreased consistently over nearly two decades. These findings likely reflect evolving clinical practice, including dose minimization strategies to reduce toxicity. Patient medians proved robust over time and may serve as a useful adjunct to conventional quality control, particularly when commercial control materials do not fully mimic patient sample behavior.

INTRODUCTION: Acute kidney injury (AKI) criteria and staging are based on serum creatinine and urine output, but serum cystatin C performs better at estimating glomerular filtration rate (GFR) in critically ill patients. Accordingly, a cystatin C-based AKI staging system was developed and its performance studied in critically ill patients.

METHODS: AKI stages according to Kidney Disease: Improving Global Outcomes (KDIGO) creatinine criteria were converted to corresponding cystatin C-based stages using 14-day mortality in 9424 critically ill patients from 3 Swedish hospitals followed for 5.6 years (median interquartile range: 2.8-7.2). Model performance was evaluated using Cox regression on long-term mortality adjusted for age, gender, comorbidities, and unit type. An independent cohort (n = 434) was used for validation.

RESULTS: KDIGO stages corresponded to the following: Stage 1: increase in cystatin C 1.40 to 1.59 times baseline within 7 days or ≥ 0.44 mg/l within 48 hours; Stage 2: 1.60 to 2.09 times baseline; and Stage 3: above 2.10 times baseline or ≥ 2.80 mg/l. Cystatin C-based versus creatinine-based staging identified 11% more AKI and 10% more Stage 3. Patients reclassified to AKI by cystatin C from no AKI had a higher risk of death of 1.36 (1.24-1.49), whereas those reclassified vice versa had a lower risk 0.71 (0.56-0.91). These findings were consistent irrespective of infection status for 30-day mortality. In the validation cohort, reclassification to a higher stage by cystatin C was an independent predictor of increased risk of death.

CONCLUSION: In critically ill patients, cystatin C-based staging identified more AKI than KDIGO criteria, and these patients had increased short- and long-term mortality.

Infectious diseases remain a major cause of mortality and disability worldwide. This burden is driven, in part, by antimicrobial resistance (AMR) and the re-emergence of epidemic and pandemic threats, underscoring the need for translational research to address knowledge gaps exposed by recent pandemics. Despite significant advances enabled by antibiotics and antivirals, their effectiveness is increasingly constrained by resistance development, limited pathogen spectra, and prolonged development timelines that fail to keep pace with rapidly shifting epidemiology. Diagnostic limitations impede timely pathogen identification and hinder the development of treatment regimens informed by pathogen mechanisms of action. Severe infections frequently involve dysregulated host responses, including hyperinflammation, inflammasome activation, and endothelial or immunothrombotic injury, which may progress to sepsis, immunoparalysis, or chronic sequelae, highlighting the limitations of pathogen-centered paradigms. Conventional biomarkers and culture-based microbiology are often slow or nonspecific, while molecular assays may not reliably distinguish colonization from active infection or capture host-response heterogeneity shaped by age, immune competence, and disease stage. This review synthesizes mechanistic and translational insights across three interrelated axes: (i) host–pathogen interactions, with a focus on innate immune sensing networks (e.g., Toll-like receptors, inflammasomes, RIG-I-like receptors, and cGAS-STING) and microbial replication and immune evasion strategies; (ii) clinical and public health implications, spanning acute organ dysfunction syndromes, post-acute infection syndromes, and AMR-driven health system strain; and (iii) emerging therapeutics along a continuum of pathogen-, virulence-, host-, and immune-directed approaches. Emphasis is placed on anti-virulence therapeutics, bacteriophage therapy, monoclonal antibodies, and engineered immune modalities within frameworks of quantitative translational pharmacology and implementation science. Finally, an integrative conceptual framework encompassing mechanistic phenotypes, host-response diagnostics, and stage-adapted therapeutic combinations is proposed to guide rational intervention across endemic infections and future pandemic preparedness.

Background/Objectives: Vitamin B₁₂ (cobalamin) and folate (vitamin B₉) are essential cofactors in one-carbon metabolism required for DNA synthesis, methylation, and genomic stability. Deficiencies in these nutrients can cause megaloblastic anemia, neurological dysfunction, and hyperhomocysteinemia, linking micronutrient imbalance to cardiovascular and neurocognitive outcomes. Population-based surveillance of these biomarkers provides insight into nutritional trends and supports analytical standardization.

Methods: This retrospective study included all routine plasma (P) vitamin B₁₂ and folate measurements performed at Uppsala University Hospital from 2005 to 2024 (n = 647,302 and 578,509, respectively). Data were extracted from the laboratory information system and summarized using annual medians, percentile distributions, and coefficients of variation (CV). Linear regression was used to validate the method comparison and assess the impact of the 2021 transition from the Abbott Architect to the Roche cobas platform. Descriptive statistics summarized the temporal and seasonal patterns of P-vitamin B₁₂ and P-folate.

Results: Median P-vitamin B₁₂ concentrations remained stable (340–370 pmol/L; median CV = 4.6%), while P-folate increased from 10.5 to 15.5 nmol/L (median CV = 12.9%) from 2005 to 2024. Low P-folate (<7 nmol/L) was observed in 7.1% of measurements and low or borderline P-vitamin B₁₂ (<250 pmol/L) in 22.6%. Females exhibited slightly higher concentrations of both analytes. Although no clear seasonal pattern was observed, small biological effects cannot be excluded. Sample volumes decreased during the summer. The transition to Roche assays introduced measurable methodological shifts, particularly for P-folate.

Conclusions: Levels of P-vitamin B₁₂ remained stable over two decades, while P-folate status increased modestly. This reflects both dietary influences and assay-related differences following the 2021 platform transition. Continuous surveillance of biomarker medians provides a sensitive tool for detecting analytical drift and for monitoring long-term nutritional trends in clinical populations.