Duplex Shiny app quantification of the sepsis biomarkers C-reactive protein and interleukin-6 in a fast quantum dot labeled lateral flow assay

Fast point-of-care (POC) diagnostics represent an unmet medical need and include applications such as lateral flow assays (LFAs) for the diagnosis of sepsis and consequences of cytokine storms and for the treatment of COVID-19 and other systemic, inflammatory events not caused by infection. Because of the complex pathophysiology of sepsis, multiple biomarkers must be analyzed to compensate for the low sensitivity and specificity of single biomarker targets. Conventional LFAs, such as gold nanoparticle dyed assays, are limited to approximately five targets-the maximum number of test lines on an assay. To increase the information obtainable from each test line, we combined green and red emitting quantum dots (QDs) as labels for C-reactive protein (CRP) and interleukin-6 (IL-6) antibodies in an optical duplex immunoassay. CdSe-QDs with sharp and tunable emission bands were used to simultaneously quantify CRP and IL-6 in a single test line, by using a single UV-light source and two suitable emission filters for readout through a widely available BioImager device. For image and data processing, a customized software tool, the MultiFlow-Shiny app was used to accelerate and simplify the readout process. The app software provides advanced tools for image processing, including assisted extraction of line intensities, advanced background correction and an easy workflow for creation and handling of experimental data in quantitative LFAs. The results generated with our MultiFlow-Shiny app were superior to those generated with the popular software ImageJ and resulted in lower detection limits. Our assay is applicable for detecting clinically relevant ranges of both target proteins and therefore may serve as a powerful tool for POC diagnosis of inflammation and infectious events.

Score performance of SAPS 2 and SAPS 3 in combination with biomarkers IL-6, PCT or CRP

OBJECTIVE

We aimed to evaluate the effects of combining the Simplified-Acute-Physiology-Score (SAPS) 2 or the SAPS 3 with Interleukin-6 (IL-6) or Procalcitonin (PCT) or C-Reactive Protein (CRP) concentrations for predicting in-hospital mortality.

MATERIAL AND METHODS

This retrospective study was conducted in an interdisciplinary 22-bed intensive care unit (ICU) at a German university hospital. Within an 18-month period, SAPS 2 and SAPS 3 were calculated for 514 critically ill patients that were admitted to the internal medicine department. To evaluate discrimination performance, the area under the receiver operating characteristic curves (AUROCs) and the 95% confidence intervals (95% CIs) were calculated for each score, exclusively or in combination with IL-6 or PCT or CRP. DeLong test was used to compare different AUROCs.

RESULTS

The SAPS 2 exhibited a better discrimination performance than SAPS 3 with AUROCs of 0.81 (95% CI, 0.76-0.86) and 0.72 (95% CI, 0.66-0.78), respectively. Overall, combination of the SAPS 2 with IL-6 showed the best discrimination performance (AUROC 0.82; 95% CI, 0.77-0.87), albeit not significantly different from SAPS2. IL-6 performed better than PCT and CRP with AUROCs of 0.75 (95% CI, 0.69-0.81), 0.72 (95% CI, 0.66-0.77) and 0.65 (95% CI, 0.59-0.72), respectively. Performance of the SAPS 3 improved significantly when combined with IL-6 (AUROC 0.76; 95% CI, 0.69-0.81) or PCT (AUROC 0.73; 95% CI, 0.67-0.78).

CONCLUSIONS

Our analysis provided evidence that the risk stratification performance of the SAPS 3 and, to a lesser degree, also of the SAPS 2 can increase when combined with IL-6. A more accurate detection of aberrant or dysregulated systemic immunological responses (by IL-6) may explain the higher performance achieved by SAPS 3 + IL-6 vs. SAPS 3. Thus, implementation of IL-6 in critical care scores can improve prediction outcomes, especially in patients experiencing acute inflammatory conditions; however, statistical results may vary across hospital types and/or patient populations with different case mix.

Time-resolved fluorescent immunoassay-based combined detection of procalcitonin, C-reactive protein, heparin binding protein, and serum amyloid A1 to improve the diagnostic accuracy of early infection

BACKGROUND

Serological tests are indispensable in the diagnosis of early infection. At present, only procalcitonin (PCT) and C-reactive protein (CRP) are commonly used in clinical practice. Recently, serum amyloid A1 (SAA1) and heparin binding protein (HBP) have been shown to be new biomarkers, because SAA1 is highly sensitive and specific for viral infections, and HBP is predictive for septic shock. In this study, PCT, CRP, HBP, and SAA1 were detected in different combinations to improve the diagnostic accuracy of early infection using the biotin-avidin amplifying system-based time-resolved fluorescent immunoassay (BA-TRFIA).

METHODS

A time-resolved fluorescent immunoassay for PCT, CRP, HBP, and SAA1 was developed and then tested in a clinical setting. All experiments were carried out using the DR6608 time-resolved fluorescent immunoassay analyzer.

RESULTS

The cutoff values of PCT, CRP, HBP, and SAA1 were 0.05 μg/L, 5.59 mg/L, 3.83 μg/L, and 1.56 mg/L, respectively. The area under the ROC curve (AUC) showed that PCT ˃ SAA1 ˃ CRP ˃ HBP > 0.8. A methodological comparison of the results showed that a combination of the four biomarkers had the highest accuracy for the diagnosis of infectious diseases.

CONCLUSION

The time-resolved fluorescent immunoassay-based combined detection of PCT, CRP, HBP, and SAA1 was shown to significantly improve the diagnostic accuracy of early infection. Thus, our results indicate that combined detection based on BA-TRFIA may represent a promising strategy in the clinical diagnosis of infection.