Current analytical strategies for C-reactive protein quantification in blood

C-Reactive Protein and Brain Natriuretic Peptides Harmonization

The harmonization of laboratory biomarkers is pivotal in ensuring consistent and reliable diagnostic outcomes across different clinical settings. This systematic review examines the harmonization of C-Reactive Protein (CRP) and N-Terminal Prohormone of Brain Natriuretic Peptide (NT-proBNP) measurements, both of which are jointly utilized in the diagnosis and management of cardiovascular diseases. To identify relevant studies, we searched the PubMed electronic database using specific medical subject headings and keywords such as C-Reactive Protein, CRP, high sensitivity C-Reactive Protein (hs-CRP), N-terminal pro B-type natriuretic peptide, and NT-proBNP, focusing on publications from June 1 to September 26, 2021. The query filtered studies to include only those in English involving human subjects. From our search, 97 articles met the inclusion criteria and were included for in-depth analysis. Despite their widespread use, significant variability remains in the measurements of CRP and NT-proBNP due to a lack of standardized pre-analytical, analytical, and post-analytical practices. This review highlights the consequences of this variability on clinical decision-making and patient outcomes and emphasizes the need for international standards and guidelines to achieve better harmonization. Our findings advocate for the establishment of universal protocols to enhance the reliability of these biomarker measurements across different clinical environments, ensuring improved healthcare delivery.

Gold single atom-based aptananozyme as an ultrasensitive and selective colorimetric probe for detection of thrombin and C-reactive protein

An ultra-efficient biocatalytic peroxidase-like Au-based single-atom nanozyme (Au-SAzymes) has been synthesized from isolated Au atoms on black nitrogen doped carbon (Au-N-C) using a simple complexation-adsorption-pyrolysis method. The atomic structure of AuN4 centers in black carbon was revealed by combined high-resolution transmission electron microscopy/high-angle annular dark-field scanning transmission electron microscopy. The Au-SAzymes showed a remarkable peroxidase activity with 1.7 nM as Michaelis-Menten constant, higher than most previously reported SAzyme activity. Density functional theory and Monte Carlo calculations revealed the adsorption of H2O2 on AuN4 with formation of OH* and O*. Molecular recognition was greatly enhanced via label-free integration of thiol-terminal aptamers on the surface of single Au atoms (Aptamer/Au-SAzyme) to design off-on ultrasensitive aptananozyme-based sensor for detecting thrombin and CRP with 550 pM and 500 pg mL-1 limits of detection, respectively. The Aptamer/Au-SAzyme showed satisfactory accuracy and precision when applied to the serum and plasma of COVID-19 patients. Due to the maximum Au atom utilization, approximately 3636 samples can be run per 1 mg of gold, highlighting the commercialization potential of the developed Aptamer/Au-SAzyme approach.

Ultrasensitive aptamer-functionalized Cu-MOF fluorescent nanozyme as an optical biosensor for detection of C-reactive protein

In the present work, an aptasensing method based on integration of RNA on Cu-MOF was developed for detection of C-Reactive Protein (CRP). Cu-MOF showed stimulated fluorescence and mimetic peroxidase enzymatic activity at the time and can be used as dual-signal transduction. CRP binding RNA was used as a highly selective recognition element and immobilized on the Cu-MOF. The immobilized RNA can block the peroxidase activity and fluorescence of the signal traducer probe. Adding CRP to the RNA/Cu-MOF will release RNA from the surface of Cu-MOF and recover both the stimulated fluorescence and peroxidase activity. A biosensor was built for detection of CRP using the two modes of transduction, either colorimetry or fluorometry. A dynamic linear range was obtained from 0.1 to 50 ng mL ^-1with a limit of detection (LOD) as small as 40 pg mL ^-1was calculated in fluorescence mode and 240 pg mL ^-1 as LOD in colorimetry mode. The LODs are lower than the LOD of nephelometric techniques used in clinical practice and is comparable to the normal clinical cutoff value in high-sensitivity CRP assays (1 μg/mL). The aptasensor was successfully applied for detection of CRP in Covid-19 patients with spike recoveries between 84 and 102% and RSD from 0.94% to 2.05%.

Epitope mapping of antibodies in C-reactive protein assay kits by hydrogen-deuterium exchange mass spectrometry explains differential results across kits

C-Reactive protein (CRP) is an important marker for in vitro diagnosis (IVD) of inflammation. However, CRP immunoturbidimetric kits from different manufacturers exhibit inconsistency in evaluation, making clinical diagnosis challenging. The use of immunological methods in diagnosis means that the differences in epitopes across kits may directly lead to inconsistent results. Therefore, to provide consistent results, it is essential to perform epitope mapping of different kits. The composition of antibodies in a single kit is typically complex, with a combination of polyclonal antibodies or monoclonal antibodies. Here, we show an epitope screening strategy for complex antibodies in a kit based on hydrogen-deuterium exchange mass spectrometry (HDX-MS). We applied this workflow to successfully map the epitopes for three kits from three different manufacturers and compared their quantitative results. We obtained different quantitative results using kits from different manufacturers upon epitope mapping, confirming the correlation between the quantitative results and the epitopes. Thus, we have established a workflow based on HDX-MS to screen epitopes in IVD kits. This work helps determine the quantitative accuracy of a kit based on structural information, can guide the design and production of IVD reagents, and further improves the accuracy of IVD.

Laser-patterned paper-based flow-through filters and lateral flow immunoassays to enable the detection of C-reactive protein

We report the use of a laser-based fabrication process in the creation of paper-based flow-through filters that when combined with a traditional lateral flow immunoassay provide an alternative pathway for the detection of a pre-determined analyte over a wide concentration range. The laser-patterned approach was used to create polymeric structures that alter the porosity of the paper to produce porous flow-through filters, with controllable levels of porosity. When located on the top of the front end of a lateral flow immunoassay the flow-through filters were shown to block particles (of known sizes of 200 nm, 500 nm, 1000 nm and 3000 nm) that exceed the effective pore size of the filter while allowing smaller particles to flow through onto a lateral flow immunoassay. The analyte detection is based on the use of a size-exclusive filter that retains a complex (∼3 μm in size) formed by the binding of the target analyte with two antibodies each of which is tagged with different-sized labels (40 nm Au-nanoparticles and 3 μm latex beads), and which is larger than the effective pore size of the filter. This method was tested for the detection of C-reactive protein in a broad concentration range from 10 ng/ml to 100,000 ng/ml with a limit-of-detection found at 13 ng/ml and unlike other reported methods used for analyte detection, with this technique we are able to counter the Hook effect which is a limiting factor in many lateral flow immunoassays.

Development of a Point-of-Care System Based on White Light Reflectance Spectroscopy: Application in CRP Determination

The development of methods and miniaturized systems for fast and reliable quantitative determinations at the Point-of-Care is a top challenge and priority in diagnostics. In this work, a compact bench-top system, based on White Light Reflectance Spectroscopy, is introduced and evaluated in an application with high clinical interest, namely the determination of C-Reactive protein (CRP) in human blood samples. The system encompassed all the necessary electronic and optical components for the performance of the assay, while the dedicated software provided the sequence and duration of assay steps, the reagents flow rate, the real-time monitoring of sensor response, and data processing to deliver in short time and accurately the CPR concentration in the sample. The CRP assay included two steps, the first comprising the binding of sample CRP onto the chip immobilized capture antibody and the second the reaction of the surface immunosorbed CRP molecules with the detection antibody. The assay duration was 12 min and the dynamic range was from 0.05 to 200 μg/mL, covering both normal values and acute inflammation incidents. There was an excellent agreement between CRP values determined in human plasma samples using the developed device with those received for the same samples by a standard diagnostic laboratory method.

Clinical and prognostic implications of C-reactive protein levels in myocardial infarction with nonobstructive coronary arteries

BACKGROUND

Myocardial infarction with nonobstructive coronary arteries (MINOCA) is a heterogeneous condition. Recent studies suggest that MINOCA patients may have a proinflammatory disposition. The role of inflammation in MINOCA may thus be distinct to myocardial infarction with significant coronary artery disease (MI-CAD).

HYPOTHESIS

We hypothesized that inflammation reflected by C-reactive protein (CRP) levels might carry unique clinical information in MINOCA.

METHODS

This retrospective registry-based cohort study (SWEDEHEART) included 9916 patients with MINOCA and 97 970 MI-CAD patients, used for comparisons. Multivariable-adjusted regressions were applied to investigate the associations of CRP levels with clinical variables, all-cause mortality and major cardiovascular events (MACE) during a median follow-up of up to 5.3 years.

RESULTS

Median admission CRP levels in patients with MINOCA and MI-CAD were 5.0 (interquartile range 2.0-9.0) mg/dl and 5.0 (interquartile range 2.1-10.0 mg/dl), respectively. CRP levels in MINOCA exhibited independent associations with various cardiovascular risk factors, comorbidities and estimates of myocardial damage. The association of CRP with peripheral artery disease tended to be stronger compared to MI-CAD. The associations with female sex, renal dysfunction and myocardial damage were stronger in MI-CAD. CRP independently predicted all-cause mortality in MINOCA (hazard ratio 1.22 [95% confidence interval 1.17-1.26]), similar to MI-CAD (p interaction = 0.904). CRP also predicted MACE (hazard ratio 1.08 [95% confidence interval 1.04-1.12]) but this association was weaker compared to MI-CAD (p interaction<.001).

CONCLUSIONS

We found no evidence indicating the presence of a specific inflammatory pattern in acute MINOCA compared to MI-CAD. However, CRP levels were independently, albeit moderately associated with adverse outcome.

Nanodiagnostic Attainments and Clinical Perspectives on C-Reactive Protein: Cardiovascular Disease Risks Assessment

Cardiovascular disease (CVD) has become one of the leading causes of morbidity and mortality in both men and women. According to the World Health Organization (WHO), ischemic heart disease is the major issue due to the narrowing of the coronary artery by plaque formation on the artery wall, which causes an inadequate flow of oxygen and blood to the heart and is called 'coronary artery disease'. The CVD death rate increased by up to 15% in 2016 (~17.6 million) compared to the past decade. This tremendous increment urges the development of a suitable biomarker for rapid and early diagnosis. Currently, C-reactive protein (CRP) is considered an outstanding biomarker for quick and accurate outcomes in clinical analyses. Various techniques have also been used to diagnose CVD, including surface plasmon resonance (SPR), colorimetric assay, enzyme-linked immunosorbent assay (ELISA), fluoro-immunoassays, chemiluminescent assays, and electrical measurements. This review discusses such diagnostic strategies and how current, cutting-edge technologies have enabled the development of high-performance detection methodologies. Concluding remarks have been made concerning the clinical significance and the use of nanomaterial in medical diagnostics towards nanotheranostics.

A sensitive and quantitative prognosis of C-reactive protein at picogram level using mesoporous silica encapsulated core-shell up-conversion nanoparticle based lateral flow strip assay

C- reactive protein (CRP) is a sensitive indicator for infectious or inflammatory diseases in human which can reflect the body's inflammation latency and early pathophysiological changes. The most common detection method of serum CRP is ELISA that has been proved to be expensive and time-consuming, restricting its use in point-of-care application. In this paper, we demonstrated a lateral flow system for CRP quantification by using mesoporous silica (mSiO₂) coated up-converting nanoparticles (UCNPs) (denoted as UCNPs@mSiO₂) as fluorescent labels. The up-converting core can emit strong green fluorescence signals under NIR excitation light (980 nm) with excellent photostability, high signal-to-noise ratio and low background fluorescence. By wrapping ultrathin mSiO₂ outside, the core-shell structured UCNPs@mSiO₂ exhibits good dispersity and stability meanwhile maintains strong fluorescence emission. Besides, the mSiO₂ shell provides further functionalities for antibody linkage. By using a portable fluorescence sensor, we reached a CRP detection limit of 0.05 ng/mL and a linear range from 0.1 ng/mL-50 ng/mL, and the detection time was no more than 8 min. The lateral flow test strips exhibit great stability in CRP quantification (CV%<5) and have a life time of more than 1 week at ambient temperature. Furthermore, the proposed system can work with a cloud-enabled smartphone through Bluetooth for Internet of Medical Things application. This CRP detection method proves to be rapid and easy-operated, which has great potential in early inflammatory disease perception in the point-of-care tests and future's 5G-enabled remote healthcare management.

Recent Trends in Electrochemical Sensors for Vital Biomedical Markers Using Hybrid Nanostructured Materials

This work provides a succinct insight into the recent developments in electrochemical quantification of vital biomedical markers using hybrid metallic composite nanostructures. After a brief introduction to the biomarkers, five types of crucial biomarkers, which require timely and periodical monitoring, are shortlisted, namely, cancer, cardiac, inflammatory, diabetic and renal biomarkers. This review emphasizes the usage and advantages of hybrid nanostructured materials as the recognition matrices toward the detection of vital biomarkers. Different transduction methods (fluorescence, electrophoresis, chemiluminescence, electrochemiluminescence, surface plasmon resonance, surface-enhanced Raman spectroscopy) reported for the biomarkers are discussed comprehensively to present an overview of the current research works. Recent advancements in the electrochemical (amperometric, voltammetric, and impedimetric) sensor systems constructed with metal nanoparticle-derived hybrid composite nanostructures toward the selective detection of chosen vital biomarkers are specifically analyzed. It describes the challenges involved and the strategies reported for the development of selective, sensitive, and disposable electrochemical biosensors with the details of fabrication, functionalization, and applications of hybrid metallic composite nanostructures.

Evaluation of INSTAND e.V.'s external quality assessment for C-reactive protein and procalcitonin

Background

The purpose of this paper was to analyze the general diagnostic strength and performance of in vitro diagnostics for C-reactive protein and procalcitonin based on the results of external quality assessment schemes (EQAs).

Methods

We analyzed qualitative and quantitative data on both markers collected by the Society for Promotion Quality Assurance in Medical Laboratories (INSTAND e.V.) from 20 EQAs. The C-reactive protein evaluation was method-specific and the procalcitonin evaluation manufacturer-specific (pseudonymized). Coefficients of variation were determined in order to evaluate interlaboratory comparability and the performance of individual laboratories during the analyzed period was examined.

Results

Overall most of our participants were able to correctly distinguish the positive from the negative samples, but we occasionally observed also false-positive results for the immunological detection of C-reactive protein. For the semi-quantitative results of C-reactive protein we observed an overall median difference below 5% except for dry chemistry methods (≤ 21%). For procalcitonin two manufacturer collectives showed a good comparability, while one manufacturer detected up to 42% higher results. The coefficients of variation are promising for both analytes even though they surpass the manufacturer’s indication for some collectives. The performance of individual laboratories during the analyzed period was more stable for C-reactive protein than for procalcitonin.

Conclusion

In-vitro diagnostic testing for C-reactive protein and procalcitonin showed promising results in our EQAs but still further improvements are needed. We recommend stepping up research on reference measurement methods for both parameters to possibly enhancing the accuracy and diagnostic strength of such assays.

Functionalized Gold Nanoparticles for the Detection of C-Reactive Protein

C-reactive protein (CRP) is a very important biomarker of infection and inflammation for a number of diseases. Routine CRP measurements with high sensitivity and reliability are highly relevant to the assessment of states of inflammation and the efficacy of treatment intervention, and require the development of very sensitive, selective, fast, robust and reproducible assays. Gold nanoparticles (Au NPs) are distinguished for their unique electrical and optical properties and the ability to conjugate with biomolecules. Au NP-based probes have attracted considerable attention in the last decade in the analysis of biological samples due to their simplicity, high sensitivity and selectivity. Thus, this article aims to be a critical and constructive analysis of the literature of the last three years regarding the advances made in the development of bioanalytical assays based on gold nanoparticles for the in vitro detection and quantification of C-reactive protein from biological samples. Current methods for Au NP synthesis and the strategies for surface modification aiming at selectivity towards CRP are highlighted.

A novel silanization agent based single used biosensing system: Detection of C-reactive protein as a potential Alzheimer's disease blood biomarker

This paper illustrates a new and sensitive electrochemical immunosensor for the analysis of C-reactive protein. Indium Tin Oxide (ITO) disposable sheets were modified by using 3-cyanopropyltrimethoxysilane (CPTMS) self-assembled monolayers (SAMs) for the first time for immobilizing the anti-CRP antibody via covalent interactions without the need for any cross-linking agent. Cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS), as well as square wave voltammetry (SWV) methods were applied to characterize immobilization steps of anti-CRP and to determine the CRP concentration. The optimization of the fabricated parameters and the analytical performance of the biosensor were widely evaluated. Charge transfer resistance changes were highly linear and sensitive with CRP concentration of 3.25-208 fg mL^-1 range and associated with a limit of detection of 0.455 fg mL^-1. This impedimetric biosensing system have excellent repeatability, reproducibility and reusability. Moreover, the binding characterization of CRP to anti-CRP was monitored by a single frequency impedance technique. The amount of CRP in human serum samples were analyzed by fabricated biosensor to determine the feasibility of the biosensing system in medical purposes. We suggest that CPTMS, a new silanization agent, is ideal in biosensor applications.

Quantitative and rapid detection of C-reactive protein using quantum dot-based lateral flow test strip

A novel QD-based immunoassay on a paper-based lateral flow system has been developed to quantitatively detect C-reactive protein (CRP). Different standard CRP antigens from 1 to 200 μg mL^-1 were diluted 200-fold and only 60 μL diluted sample were needed to load onto the sample pad. The QD fluorescence signals on the test line and the control line were able to be observed within 3 min after the initiation of assay, and the limit of detection was as sensitive as 0.30 ng mL^-1 by measuring the fluorescence intensity immediately afterwards with fluorescence immunoassay analyzer. The linearity on the detection of QD fluorescence signals has been established well in the range of 0.5 ng mL^-1 and 1 μg mL^-1 for CRP. The precision of the assay has been confirmed for low coefficient of variation (CV), satisfying less than 15% (intra-assay and inter-assay), and the accuracy of assay meets the requirements with the mean recovery of the control was 102.63%. These results indicated that such newly developed platform was reliable with high sensitivity, rapidness, and could cover a broad range of target concentrations. Furthermore, a total of 135 human serum clinical samples with inflammation or infection with the concentration of CRP from 0.2 to 200 μg mL^-1 has been used to check the performance of this QD-based LFIA, it correlated very well with Roche Tina-quant CRP (Latex) (r = 0.966, n = 135).

Sandwich NP-based biobarcode assay for quantification C-reactive protein in plasma samples

A NP-based biobarcode for C-reactive protein (CRP) quantification in plasma samples is reported for the first time. The assay uses capture antibody functionalized magnetic beads (pAbCRP2-MP), multifunctional oligonucleotide encoded probes modified with a detection antibody (pAbCRP1-ePSP), and a fluorescent DNA microarray. Thus, magnetic beads are added to the sample to form immunocomplexes that will be isolated, to then add the codified particles to form a sandwich complex with both particles and the target protein, subsequently the complexes are treated to release the oligonucleotide codes, which are finally hybridized in a fluorescent DNA microarray. The assay has been implemented to the analysis of plasma samples being able to quantify this biomarker within 900 ng mL^-1 to 12500 ng mL^-1 with an excellent accuracy (mean of recovery of 99.5 ± 4.2%, N = 3). The CRP biobarcode has been used on a small pilot clinical study in which plasma samples from patients suffering different pathologies, most of them related to cardiovascular diseases (CVDs). The samples have been analyzed and the results compared to a reference method demonstrating that the assay can be useful for monitoring this biomarker on patients being suspicious to be under risk of suffering CVDs or other diseases involving inflammatory processes.

Mass spectrometry-based approaches to targeted quantitative proteomics in cardiovascular disease

Mass spectrometry-based proteomics methodology has become an important tool in elucidating some of the underlying mechanisms involved in cardiovascular disease. The present review provides details on selected important protein targets where highly selective and specific mass spectrometry-based approaches have led to important new findings and provided new mechanistic information. The role of six proteins involved in the etiology of cardiovascular disease (acetylated platelet cyclooxygenase-1, serum apolipoprotein A1, apolipoprotein C-III, serum C-reactive protein, serum high mobility group box-1 protein, insulin-like growth factor I) and their quantification has been discussed. There are an increasing number of examples where highly selective mass spectrometry-based quantification has provided new important data that could not be obtained with less labor intensive and cheaper immunoassay-based procedures. It is anticipated that these findings will lead to significant advances in a number of important issues related to the role of specific proteins in cardiovascular disease. The availability of a new generation of high-resolution high-sensitivity mass spectrometers will greatly facilitate these studies so that in the future it will be possible to analyze serum proteins of relevance to cardiovascular disease with levels of specificity and/or sensitivity that cannot be attained by immunoassay-based procedures.

In vivo porcine lipopolysaccharide inflammation models to study immunomodulation of drugs

Lipopolysaccharide (LPS), a structural part of the outer membrane of Gram-negative bacteria, is one of the most effective stimulators of the immune system and has been widely applied in pigs as an experimental model for bacterial infection. For this purpose, a variety of Escherichia coli serotypes, LPS doses, routes and duration of administration have been used. LPS administration induces the acute phase response (APR) and is associated with dramatic hemodynamic, clinical and behavioral changes in pigs. Pro-inflammatory cytokines, including tumor necrosis factor α (TNF-α), interleukin (IL)-1 and IL-6 are involved in the induction of the eicosanoid pathway and the hepatic production of acute phase proteins, including C-reactive protein (CRP), haptoglobin (Hp) and pig major acute phase protein (pig-MAP). Prostaglandin E2 (PGE2) and thromboxane A2 (TXA2) play a major role in the development of fever and pulmonary hypertension in LPS-challenged pigs, respectively. The LPS-induced APR can be modulated by drugs. Steroidal and nonsteroidal anti-inflammatory drugs ((N)SAIDs) possess anti-inflammatory, antipyretic and analgesic properties through (non)-selective central and peripheral cyclooxygenase (COX) inhibition. Antimicrobial drugs, especially macrolide antibiotics, which are commonly used in veterinary medicine for the treatment of bacterial respiratory diseases, have been recurrently reported to exert clinically important immunomodulatory effects in human and murine research. To investigate the influence of these drugs on the clinical response, production of pro-inflammatory cytokines, acute phase proteins (APP) and the course of the febrile response in pigs, in vivo LPS inflammation models can be applied. Yet, to date, in vivo research on the immunomodulatory properties of antimicrobial drugs in these models in pigs is largely lacking. This review provides acritical overview of the use of in vivo porcine E. coli LPS inflammation models for the study of the APR, as well as the potential immunomodulatory properties of anti-inflammatory and antimicrobial drugs in pigs.

Surface plasmon resonance-based immunoassay for human C-reactive protein

A rapid and highly-sensitive surface plasmon resonance (SPR)-based immunoassay (IA) has been developed and validated for detecting human C-reactive protein (CRP), a specific biomarker for inflammatory and metabolic disorders, and infections.

Magnetic chemiluminescent immunoassay for human C-reactive protein on the centrifugal microfluidics platform

Schematic of the LabDisk-based hCRP MCIA. The antibody-coated dynabeads are sequentially transported through the immunoassay buffers by magnetic actuation. Finally the chemiluminescence signal is acquired from a detection cavity.