Fluorescence Immunochromatography Research Articles

Quantitative detection of mpox antigen using time-resolved fluorescence immunochromatography.

Recently, concern has been raised about the spread of human mpox virus, and the demand for rapid detection reagents for mpox virus has increased. This study aims to establish a time-resolved fluorescence immunochromatography (TRFICO) method for qualitative/quantitative detection of mpox virus. A double-antibody sandwich TRFICO method was optimized and established using mpox recombinant fusion antigen and its paired monoclonal antibody. The test performance of the method was evaluated using mpox fusion antigen and control serum, including sensitivity, linearity range, specificity, precision, and reference interval. We successfully established a TRFICO method for qualitative/quantitative detection of mpox antigen, its linearity range 0-100ng/mL, analytical sensitivity 0.017ng/mL, and reference intervals greater than 0.045ng/mL. No cross-reaction was detected with various poxvirus and clinical negative controls, with good specificity. All average recoveries of the intra- and inter-batch ranged from 81.33% to 97.83%, and all CVs were below 10%. Additionally, the TRFICO strips can be stably stored at 37°C for 7days without significant changes in the fluorescence intensity. This TRFICO method, with high sensitivity, linearity range, specificity, precision, and stability with 16-min detection time, provides a new option for qualitative/quantitative and convenient testing of mpox virus.

Development of time-resolved fluorescence immunochromatography and ic-ELISA based on monoclonal antibodies specifically recognizing fumonisin B1

Fumonisins (FBs) are mycotoxins primarily synthesized by Fusarium moniliformis. Among these, FB1 exhibits not only high toxicity towards humans and animals but also carcinogenic properties. The global prevalence of FB1 contamination in cereals and related products, particularly maize, is alarmingly significant. Consequently, the accurate determination of FB1 levels in cereals holds immense importance. In this study, highly sensitive monoclonal antibodies specifically targeting FB1 were prepared and utilized for the establishment of a time-resolved fluorescence immunochromatographic assay (TRFIC) to detect FB1. The parameters of antibody labeling with time-resolved fluorescent microspheres were optimized. The detection time was significantly reduced to 6 min. The limits of detection (LOD) for corn, rice, and feed were determined as 0.496–0.844 μg/kg, and the quantification (LOQ) was 0.788–1.322 μg/kg. In addition, an indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) was successfully developed. Under optimized conditions, the half inhibitory concentration (IC50) value for FB1 was determined as 2.137 μg/L. A strong correlation between the results obtained from these two methods and HPLC-MS/MS analysis was observed in the same samples tested. In conclusion, both immunological methods developed in this work are highly suitable for rapid FB1 detection in real field samples.

Designing a size exclusion-based hapten and the development of a quantitative and visual time-resolved fluorescence immunochromatography assay strip for detecting dimethomorph and flumorph in a group-specific manner

Based on the size and surface properties of dimethomorph and flumorph, we used a computer simulation-assisted size exclusion hapten design strategy to develop group-specific monoclonal antibodies that can simultaneously recognize dimethomorph and flumorph. For this, we performed quantitative and visual semi-quantitative time-resolved fluorescence immunochromatography (TRFICA) to simultaneously detect dimethomorph and flumorph in potatoes and apples. In potato samples, the visual limit of detection (vLOD) for dimethomorph and flumorph was 4 ng/mL and 8 ng/mL, respectively, whereas the quantitative limit of detection (qLOD) for dimethomorph and flumorph was 0.26 and 0.33 ng/mL, respectively. The vLOD of dimethomorph and flumorph in apple samples was 8 ng/mL, whereas the qLOD of dimethomorph and flumorph was 0.17 and 0.38 ng/mL, respectively. The average recovery of potato and apple samples ranged from 77.5% to 121.7%, which indicated that the method can be used to rapidly detect dimethomorph and flumorph in food samples.

Usefulness of a new immunochromatographic assay using fluorescent silica nanoparticles for serodiagnosis of Thai patients with amebiasis.

A fluorescence immunochromatography (FIC) kit was developed recently using fluorescent silica nanoparticles coated with a recombinant C-terminal fragment of the surface lectin intermediate subunit (C-Igl) of Entamoeba histolytica to establish rapid serodiagnosis of amebiasis. We further evaluated the system using serum samples from 52 Thai patients with amebiasis. Of the patients, 50 (96%) tested positive using FIC. The samples were also tested using enzyme-linked immunosorbent assay (ELISA) with C-Igl as the antigen. Two samples were negative on ELISA but positive on FIC. The correlation coefficient between the fluorescence intensity using FIC and the optical density value using ELISA was 0.5390, indicating a moderate correlation between the two tests. Serum samples from 20 patients with malaria and 22 patients with Clostridioides difficile infection were also tested using FIC. The false-positive rates were 4/20 (20%) and 1/22 (4%) in patients with malaria and C. difficile infection, respectively. Combining the data from the present study with our previous study, the sensitivity and specificity of FIC were determined to be 98.5% and 95.2%, respectively. The results of the 50 samples were studied using a fluorescence scope and a fluorescence intensity reader, and the findings were compared. Disagreements were found in only two samples showing near-borderline fluorescence intensity, indicating that the use of scope was adequate for judging the results. These results demonstrate that FIC is a simple and rapid test for the serodiagnosis of amebiasis.

Comparison of Plasma Concentration of Linezolid's Detection by FICA and LC-MS/MS.

Linezolid was the first totally synthetic oxazolidinone antibiotic that was approved for clinical use against Mycobacterium tuberculosis. Our study investigated the correlation and consistency of fluorescence immunochromatography assay (FICA) and high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) in measuring linezolid levels in the plasma. Plasma samples were collected from 80 to 100 tuberculosis patients. The samples were analyzed by FICA and LC-MS/MS, and linezolid levels measured by the two methods were compared by outlier test, correlation coefficient, Bland-Altman scatter plot, Deming regression analysis and bias evaluation. A total of 83 plasma samples were collected, all of which were non-outlier. The correlation coefficient of FICA and LC-MS/MS results was 0.9845. Deming regression analysis showed that the regression equation of FICA and LC-MS/MS was y = 0.2229 + 1.0076x. The medical decision levels of 2 and 7μg/mL were taken into the regression equation, and the 95% CI of 2- and 7-μg/mL bias were both within the allowed error range. The findings indicated a strong correlation between the results obtained from FICA and LC-MS/MS were consistent showed good correlation, demonstrating their equivalence in measurement.

Rapid determination of furazolidone residues in animal foods by time-resolved fluorescence immunochromatography

Although furazolidone (FZD) was completely banned from livestock production in many countries many years ago due to its mutagenicity and carcinogenicity, the abuse of FZD is still common today. Accurate and rapid detection of FZD residues in animal-derived food products is highly important for human health. Here, a time-resolved fluorescence immunochromatography (TRFI) test strip for rapid and quantitative detection of 3-amino-2-oxazolidinone (AOZ) residues in animal foods was developed and validated. Its limit of detection and limit of quantification were 0.05 and 0.14 μg/kg, respectively. The typical recovery rates were 95–105 % in chicken breast samples spiked with the AOZ standard substance at concentrations of 0.05–2 μg/kg, with a coefficient of variation value ≤8.5 %. The cross-reaction rates of the TRFI-AOZ test strips with 3-amino-5-morpholinomethyl-2-oxazolidone, semicarbazide, and 1-amino-imidazolidin-2,4-dione were less than 1 %. The newly developed TRFI test strip has high sensitivity, high specificity, cost effectiveness and user-friendly control, and is suitable for the rapid and large-scale screening of AOZ residues in animal foods.

Development of a fluorescence immunochromatography method for quantitative measurement of matrix metalloproteinase-9

ObjectiveAbnormal serum matrix metalloproteinase-9 (MMP-9) levels are closely related to the occurrence and development of many diseases. This study aimed to establish a fluorescence immunochromatography (FIC) method using the lanthanide fluorescent element europium(III) (Eu3+) for the quantitative measurement of MMP-9 in serum. Design & MethodsThe FIC method for quantifying MMP-9 was optimized and established, and the FIC test strips (FICTS) were assembled and subsequently evaluated for sensitivity, specificity and precision. Furthermore, the reference interval and clinical sensitivity/specificity were estimated using clinical healthy/positive serum samples, and a commercial ELISA was used for comparison. ResultsWe successfully established an FIC method and prepared FICTS. The analytical sensitivity of the FICTS was 0.92 ng/mL, with a linearity range of 0–1000 ng/mL. The cross-reactivity of the 7 common serum interferents was less than 1.56%. All recoveries of the intra-array and inter-array samples ranged from 102.50% to 110.99%, and all CVs were less than 5%. The reference interval of the FICTS was >161.15 ng/mL. The clinical sensitivity was 96.00%, and the specificity was 97.5%. The results of 270 clinical serum samples were highly coincident with the clinical diagnostic results. Pearson correlation analysis and Bland‒Altman plots indicated that the FICTS and commercial ELISA results were consistent with the quantitative MMP-9 concentration. ConclusionsThe designed FIC method and test strips may be suitable for point-of-care quantitative measurement of MMP-9, which provides a new method for screening for atherosclerosis, xerophthalmia, etc.

Determination of serum CA724 levels using fluorescence immunochromatography

BackgroundCarbohydrate antigen 724 (CA724) is a sensitive and specific indicator for multiple malignant tumors. The aim of this study was to establish a Eu-time resolved fluorescence immunochromatography (Eu-TRFICO) method for quantitative detection of CA724 in serum.MethodsEu-TRFICO strips were optimized and assembled. The sensitivity, specificity and precision were evaluated using CA724 standard dilutions and matrix serum. Meanwhile, the reference interval, comparison, and sensitivity/specificity were performed using clinical negative/positive gastric cancer serum samples.ResultsThe standard curve equation was y = 9.869 x − 154.12 (R2 = 0.993), and the sensitivity was 0.42 U/mL. The common interferents in serum could not affect the quantitative results with low cross-reactivities (all no more than 1.09%). All average recoveries of the intra- and interbatch ranged from 102.38 to 106.40%, and all CVs were below 10%. The reference interval of the healthy subjects was < 4.68 U/mL and the reference interval of the subjects with grade I/II gastric cancer was > 9.54 U/mL. Additionally, a high Pearson r (0.9503) and sensitivity/specificity (92.86%/94.20%) were obtained.ConclusionThis study prepared Eu-TRFICO strips with high sensitivity, specificity, precision and satisfactory clinical testing performance, which provides more options for clinical quantitative and convenient testing of CA724.

Performance evaluation of SARS-CoV-2 antigen detection in the post-pandemic era: multi-laboratory assessment.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antigen detection is an indispensable tool for epidemic surveillance in the post-pandemic era. Faced with irregular performance, a comprehensive external quality assessment (EQA) scheme was conducted by the National Center for Clinical Laboratories (NCCL) to evaluate the analytical performance and status of SARS-CoV-2 antigen tests. The EQA panel included ten lyophilized samples containing serial 5-fold dilutions of inactivated SARS-CoV-2-positive supernatants of the Omicron BA.1 and BA.5 strains and negative samples, which were classified into "validating" samples and "educational" samples. Data were analyzed according to qualitative results for each sample. A total of 339 laboratories in China participated in this EQA scheme, and 378 effective results were collected. All validating samples were correctly reported by 90.56 % (307/339) of the participants and 90.21 % (341/378) of the datasets. The positive percent agreement (PPA) was >99 % for samples with concentrations of 2×107 copies/mL but was 92.20 % (697/756) for 4×106 copies/mL and 25.26 % (382/1,512) for 8×105 copies/mL samples. Colloidal gold was the most frequently used (84.66 %, 320/378) but showed the lowest PPAs (57.11 %, 1,462/2,560) for positive samples compared with fluorescence immunochromatography (90 %, 36/40) and latex chromatography (79.01 %, 335/424). Among 11 assays used in more than 10 clinical laboratories, ACON showed a higher sensitivity than other assays. The EQA study can help to validate whether it's necessary to update antigen detection assays for manufacturers and provide participants with information about the performance of assays to take the first step toward routine post-market surveillance.

Paper-based biosensors relying on core biological immune scaffolds for the detection of procymidone in vegetables

In order to achieve a highly sensitive detection of procymidone in vegetables, three paper-based biosensors based on a core biological immune scaffold (CBIS) were developed, which were time-resolved fluorescence immunochromatography strips with Europium (III) oxide (Eu-TRFICS). Goat anti-mouse IgG and europium oxide time-resolved fluorescent microspheres formed secondary fluorescent probes. CBIS was formed by secondary fluorescent probes and procymidone monoclonal antibody (PCM-Ab). The first type of Eu-TRFICS (Eu-TRFICS-(1)) fixed secondary fluorescent probes on a conjugate pad, and PCM-Ab was mixed with a sample solution. The second type of Eu-TRFICS (Eu-TRFICS-(2)) fixed CBIS on the conjugate pad. The third type of Eu-TRFICS (Eu-TRFICS-(3)) was directly mixed CBIS with the sample solution. They solved the problems of steric hindrance of antibody labeling, insufficient exposure of antigen recognition region and easy loss of activity in traditional methods. They realized multi-dimensional labeling and directional coupling. They replaced the loss of antibody activity. And the three types of Eu-TRFICS were compared, among which Eu-TRFICS-(1) was the best detection choice. Antibody usage was reduced by 25% and sensitivity was increased by 3 times. Its detection range was 1–800 ng/mL, the limit of detection (LOD) was 0.12 ng/mL with the visible LOD (vLOD) of 5 ng/mL.

Fluorescent Immunochromatography of Vancomycin in Plasma: A Rapid and Sensitive Quantitative Analysis.

Vancomycin (VAN) has a narrow therapeutic window and variable pharmacokinetic properties, which require timely monitoring of plasma concentration to adjust the dosage for better effectiveness. A sensitive and quantitative immunochromatographic method was developed to detect vancomycin in plasma. The linear response range of the method to detect plasma vancomycin was 1.25-50 μg/mL. The intra-assay and inter-assay coefficients were 4.68% and 8.81%, respectively, while the recovery was 89.10-98.32%. The clinical comparative experiment results demonstrated a good correlation (r>0.90) between the fluorescent immunochromatographic strip test and the mass spectrum. In this study, a simple, rapid, and high-sensitivity immunochromatographic method was established for detecting vancomycin, which helped establish the basis for further application of monitoring plasma concentration.

A helper antibody based competitive fluorescence immunochromatographic assay for quantitative detection of florfenicol in poultry eggs.

Florfenicol (FF) is a chloramphenicol analogue used in animals, and florfenicol amine (FFA) is the main metabolite of FF. However, their residues in agricultural products are harmful to human health. A highly specific and sensitive assay for FF/FFA detection needs to be developed since the traditional detection methods are low sensitive. In this study, a new method for rapid quantification of FF/FFA in poultry eggs by fluorescent immunochromatographic assay (HAFIA) was established. The triple antibodies including a primary monoclonal antibody (mAb) specific to the targets FF and FFA, a secondary polyclonal antibody (pAb) labeled with Europium nanoparticles (EuNPs) and a helper monoclonal antibody (hAb) reacting with pAb but not react with mAb or target antigen are designed, which can form structural aggregation complexes in microwells with a single step of reactions. By loading the reaction sample solution, the triple-antibodies (mAb-pAb-hAb)-EuNPs complexes migrate to the test (T) line on nitrocellulose membrane of testing strip, which are competitively captured by the immobilized FF-BSA conjugates on the membrane and the FF/FFA targets in sample solution. Fluorescence on T line is read by a portable fluorescent strip reader in 10 min, and the result is given by the ratio of fluorescent intensity on T line than control (C) line. This new fluorescent testing strip with triple-antibody complexes' amplification signal has 50-fold higher sensitivity than conventional CG-LFIAs, and can detect as low as 0.01 ng/mL florfenicol and 0.1 ng/mL florfenicol amine targets from egg samples. The developed competitive fluorescent immunochromatography method based on auxiliary antibodies has the advantages of high sensitivity and specificity for the rapid and quantitative detection of FF/FFA in poultry eggs.

Comparison of a rapid fluorescence immunochromatographic test with an enzyme-linked immunosorbent assay for measurement of SARS-CoV-2 spike protein antibody neutralizing activity

BackgroundSARS-CoV-2 Spike protein Receptor Binding Domain neutralizing antibodies (NAbs-RBD) inhibit the viral binding to angiotensin-converting enzyme 2 (ACE2) receptors. We compared an ELISA and a fluorescence immunochromatography (FIC) method in NAbs-RBD detection after COVID-19 immunization. MethodSerum samples from healthcare workers (HCWs) vaccinated with BNT162b2 were collected one and four months after the second dose. NAbs-RBD (%) detection was performed using ELISA cPass™ (FDA approved) and FIC n-AbCOVID-19® assays. ResultsSamples from 200 HCWs [median age (IQR): 45(35−53)] were tested with both assays. There was a good qualitative agreement between the two methods [AUC: 0.92(95%C.I.: 0.89–0.94, P-value:0.007)]. NAbs-RBD (%), one and four months after immunization, were significantly lower with FIC compared to ELISA for all age groups (P-value<0.0001). The quantitative comparison between FIC and ELISA detected slight agreement one month after the second dose [(Lin’s Concordance Correlation Coefficient (CCC): 0.21(95%CI: 0.15–0.27)] which improved four months after the second dose [CCC: 0.6(95%CI: 0.54–0.66)]. ConclusionFIC had good qualitative agreement with ELISA in the detection of positive NAbs-RBD (%) and could be an alternative for rapid NAbs-RBD (%) testing.

Deep learning on lateral flow immunoassay for the analysis of detection data.

Lateral flow immunoassay (LFIA) is an important detection method in vitro diagnosis, which has been widely used in medical industry. It is difficult to analyze all peak shapes through classical methods due to the complexity of LFIA. Classical methods are generally some peak-finding methods, which cannot distinguish the difference between normal peak and interference or noise peak, and it is also difficult for them to find the weak peak. Here, a novel method based on deep learning was proposed, which can effectively solve these problems. The method had two steps. The first was to classify the data by a classification model and screen out double-peaks data, and second was to realize segmentation of the integral regions through an improved U-Net segmentation model. After training, the accuracy of the classification model for validation set was 99.59%, and using combined loss function (WBCE + DSC), intersection over union (IoU) value of segmentation model for validation set was 0.9680. This method was used in a hand-held fluorescence immunochromatography analyzer designed independently by our team. A Ferritin standard curve was created, and the T/C value correlated well with standard concentrations in the range of 0-500 ng/ml (R 2 = 0.9986). The coefficients of variation (CVs) were ≤ 1.37%. The recovery rate ranged from 96.37 to 105.07%. Interference or noise peaks are the biggest obstacle in the use of hand-held instruments, and often lead to peak-finding errors. Due to the changeable and flexible use environment of hand-held devices, it is not convenient to provide any technical support. This method greatly reduced the failure rate of peak finding, which can reduce the customer's need for instrument technical support. This study provided a new direction for the data-processing of point-of-care testing (POCT) instruments based on LFIA.

A highly sensitive fluorescence immunochromatography strip for thiacloprid in fruits and vegetables using recombinant antibodies

Thiacloprid (TCL) is a neonicotinoid insecticide. Its widespread use has led to high levels of residue in fruits and vegetables. Hence, it is important to detect TCL rapidly, accurately, and sensitively in fruits and vegetables. Recombinant antibodies (rAbs) can be synthesized rapidly with little batch-to-batch variation. In this study, recombinant single-chain variable fragment (scFv) antibody and full-length recombinant antibody against TCL were produced using three different expression systems (E. coli, yeast, and mammalian cell). The results of SDS-PAGE and non - competitive enzyme-linked immunosorbent assay (ELISA) indicated that the full-length rAb exhibited promising characteristics, and the IC50 value of indirect competitive ELISA (ic-ELISA) was 2.63 μg L−1. However, recombinant scFv antibody had little affinity for the antigen. To understand antibody recognition, the three-dimensional (3D) model of the variable fragment (Fv) was built via homologous modeling. The interaction between Fv and TCL was analyzed via molecular docking and the results of molecular docking showed that VAL-158, ALA-211, PHE-220, TRP-218, TRP-49, and ILE-100 were mainly responsible for antibody recognition. In addition, a time-resolved fluorescent microsphere-immunochromatographic test strip (TRFM-ICTS) was developed with a linear range and limit of detection of 0.01–10 ng mL−1 and 0.003 ng mL−1 within 15 min under optimal conditions. The IC50 value was 4.268 ng mL−1, and the recovery ranged between 79.4% and 118.6%, which was consistent with HPLC-MS. The TRFM-ICTS has great advantages in sensitivity and applicability.

Design and development of a lanthanide-labeled immunochromatographic strip for simultaneous detection of morphine, methamphetamine and ketamine in hair.

Colloidal gold immunoassay is the most widely used method in the field of drug detection. However, this method often has poor quantitative identification ability and low analytical sensitivity, which is not suitable for the analysis of hair poisoning ingredients. In order to solve these limitations, we developed an immunochromatographic test strip for simultaneously screening multiple drugs in this study. This hand-held test strip used fluorescent nanoparticles loaded with lanthanide chelates as the signal carrier of fluorescence reading, and conducted quantitative testing of various drugs based on the competitive immune reaction between the analyte and antigen. Under the optimal conditions, the competition curves of morphine (MOP), methamphetamine (MET) and ketamine (KET) were obtained on a single band. The detection limit (LOD) of this analytical method was 100-1000 times lower than that of colloidal gold test strips. The detection limits of MOP, MET and KET were 0.06 ng mL-1, 0.1 ng mL-1 and 1.0 ng mL-1, respectively. No cross-reaction was observed when morphine, methamphetamine and ketamine were tested simultaneously with this method. And 184 hair samples were tested simultaneously, and the detected amount was very close to the results of LC-MS. The immunochromatographic strip showed good stability in repeated tests, and the coefficient of variation was less than 15%. Fluorescence immunochromatography strips and handheld strip readers have the characteristics of portability, speed, ease of operation and high sensitivity, and may become powerful tools for screening drug abuse in hair in forensic medicine.

Recombinase Polymerase Amplification Combined with Fluorescence Immunochromatography Assay for On-Site and Ultrasensitive Detection of SARS-CoV-2

This study established a portable and ultrasensitive detection method based on recombinase polymerase amplification (RPA) combined with high-sensitivity multilayer quantum dot (MQD)-based immunochromatographic assay (ICA) to detect the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The RPA-MQD-based ICA method is reported for the first time and has the following advantages: (i) RPA is free from the constraints of instruments and can be promoted in point-of-care testing (POCT) scenarios, (ii) fluorescence ICA enhances the portability of detection operation so that the entire operation time is controlled within 1 h, and (iii) compared with common colorimetric-based RPA-ICA, the proposed assay used MQD to provide strong and quantifiable fluorescence signal, thus enhancing the detection sensitivity. With this strategy, the proposed RPA-MQD-based ICA can amplify and detect the SARS-CoV-2 nucleic acid on-site with a sensitivity of 2 copies/reaction, which is comparable to the sensitivity of commercial reverse transcription quantitative polymerase chain reaction (RT-qPCR) kits. Moreover, the designed primers did not cross-react with other common respiratory viruses, including adenovirus, influenza virus A, and influenza virus B, suggesting high specificity. Thus, the established portable method can sensitively detect SARS-CoV-2 nucleic acid without relying on equipment, having good application prospects in SARS-CoV-2 detection scenarios under non-lab conditions.

Ratiometric fluorescent immunochromatography for simultaneously detection of two nitrofuran metabolites in seafoods

Competitive immunochromatographic assay (ICA) has been widely used in food safety on-site monitoring. However, traditional competitive ICA relies on the change of single-signal intensity to discriminate the results, leading to limited sensitivity and accuracy of naked-eye visual inspection. In this study, we developed a sensitive ratiometric fluorescent immunochromatographic assay (RFICA) judging results based on the color changes of fluorescence. Two different color quantum dot nanobeads (QBs) were introduced as signal labels for rapid and accurate detection of 3-amino-2-oxazolidinone (AOZ) and semicarbazide (SEM) in seafoods. Under the optimal conditions, the visual detection limit for 2-NPAOZ and 2-NPSEM reached up to 1 and 0.5 ng/mL, which were 5- and 14-fold lower than that of traditional single-signal response fluorescent ICA strips. In addition, the RFICA strips were applied to real samples with acceptable recoveries of 81.33 ∼ 99.23 %. These results demonstrate that the developed RFICA platform possesses considerable potential in the on-site detection.

P412 QuicGM Aspergillus Galactomannan Ag lateral flow assay as a practical aid to diagnose invasive Aspergillosis in high-risk hematology patients

Poster session 3, September 23, 2022, 12:30 PM - 1:30 PMBackgroundEarly diagnosis of invasive aspergillosis (IA) is an important factor to improve survival, but it remains challenging. QuicGM Aspergillus Galactomannan Ag Lateral Flow Assay (LFA) is based on a fluorescence immunochromatography test using a monoclonal antibody to identify Aspergillus galactomannan antigen in serum and bronchoalveolar lavage fluid.MethodsIn this study, we analyzed the diagnostic performance of QuicGM in 120 serum samples of high-risk hematology patients [41 cases of proven (n = 4) and probable (n = 37) IA and 79 equally high-risk controls] and compared it to performance of the galactomannan (GM) [Platelia Aspergillus enzyme immunoassay (ELISA) (Bio-Rad, Marnes-la-Coquette, France)]. Probable cases defined by a positive Biorad GM in serum were also included in the cohort.ResultsUsing the same cut-off of 0.5, QuicGM was positive in 22 cases versus GM in 21 cases. However, QuicGM was false positive in 11 controls with GM only in 1 control. These false positive samples remained positive upon repeated testing with the QuicGM. The test results of QuicGM and GM correlated well with a Spearman's correlation coefficient of 0.80 (P <.001). McNemar test showed no significant difference between both tests (P = 1) and Cohen's kappa coefficient was 0.65 (CI 0.49-0.81), suggesting a substantial strength of agreement.QuicGM sensitivity (using 0.5 cutoff) was 54% versus 51% for GM. Specificity was 86% for QuicGM versus 99% for GM. Positive predictive value (PPV) was only 67% for QuicGM versus 95% for GM. Combining GM and QuicGM in serum increased sensitivity to 59%. Youden index of QuicGM in the cohort was 0.39. Using this cutoff, sensitivity was 66% and specificity was 80%. When using a higher cutoff of 0.6 for the QuicGM, specificity increased to 94% and PPV to 78%, at the cost of a decrease in sensitivity to 44%.DiscussionIncluding probable cases defined by a positive Biorad GM in serum could have led to a bias in favor of the GM.With the cutoff suggested by the company, there was a notable decrease in specificity and PPV for the QuicGM. The need to adjust this cut-off must be questioned. With the implementation of LFAs in the EORTC-MSGERG criteria, one usually strives for the same cutoff of 0.5, to assure a practical approach. However, we must remain thoughtful about slight differences in these tests. They all have their own IgG and IgM built. Caution is needed more in the setting of diagnosis than in screening.More knowledge must be obtained regarding how different hospital laboratories have implemented the LFAs.ConclusionDiagnostic performances of QuicGM and Biorad GM correlate well.Further research is necessary regarding the optimal cutoff index.

Development of a fluorescence immunochromatography for quantitative detection of cartilage oligomeric matrix protein

The purpose of this study was to develop a fluorescence chromatography method for the detection of cartilage oligomeric matrix protein (COMP) in the auxiliary diagnosis of rheumatoid arthritis (RA). The principle of double antibody sandwich method was used to prepare immunochromatographic test strips, and the performance evaluation and methodological comparison were carried out. Through the detection of clinical samples, a receiver operating characteristic (ROC) curve was obtained, and the sensitivity, specificity, positive and negative predictive values of the test strip were calculated. The linear range was 0.39-50.00 ng/mL. The coefficients of variation inter and intra batches were less than 15%. The test strip was stable at 37 ℃ for 20 days, and the variation range of fluorescence signal intensity was within 15%. There was no cross reaction with rheumatoid factor (RF) and anti-cyclic citrulline peptide (anti-CCP) antibody. Forty-eight clinical serum samples were detected in parallel with ELISA kit, and the correlation was good. The test strip prepared in this study was used to detect the sample, the cut-off value of COMP between RA patients and healthy people was 22.55 ng/mL (sensitivity 0.821, specificity 0.842, positive predictive value 0.741, negative predictive value 0.895). At the same time, the same sample was tested with ELISA kit, the sensitivity and specificity of the two methods reached more than 80%. A quantitative COMP fluorescence chromatography test strip was developed, which has the advantages of celerity, simplicity and sensitivity, and may provide rapid auxiliary diagnosis for RA patients.