Commercial Enzyme-linked Immunoassay Research Articles

Point-of-Care Detection of HER2 and CA 15-3 in Breast Cancer Patients: Dual-Channel Biosensor Implementation

Breast cancer remains a considerable health challenge, affecting numerous individuals annually. This research introduces an innovative method for detecting breast cancer utilizing dual-channel test strips capable of simultaneously assessing two key biomarkers—HER2 and CA 15-3. The test strip utilized in this study is not only cost-effective but also entirely non-invasive. The reusable device employs a printed circuit board with metal-oxide-semiconductor field-effect transistor amplification and Arduino-based control to convert voltage signals from test strips into digital readings efficiently. The device utilizes double-pulse measurement instead of direct current, effectively mitigating the screening effect. The detection limit for both biomarkers is exceptionally low at 10−15 g ml−1, surpassing commercial enzyme-linked immunoassay kits by four orders of magnitude. The sensor demonstrates remarkable sensitivity, with 78/dec for HER2 and 56/dec for CA 15-3. Human sample tests were conducted to validate the efficacy of the dual-channel strip, successfully distinguishing between healthy and cancerous groups. The results reveal significant p-values for both HER2 and CA 15-3 tests, underscoring the significance of this research. Note that this is a rapid testing process, completed in less than 2 s. These findings offer a promising avenue for swift and accurate breast cancer detection, furnishing crucial insights for early diagnosis and subsequent treatment.

Combining Bioorthogonal Chemistry with Fluorescent Silica Nanoparticles for the Ultrasensitive Detection of the HIV-1 p24 Antigen.

Early detection and viral concentration monitoring of human immunodeficiency virus in resource-poor settings are important to control disease spread and reduce mortality. Nucleic acid amplification tests are expensive for low-resource settings. Lateral flow antibody tests are not sensitive if testing is performed within 7-10 days, and these tests are not quantitative. We describe a signal enhancement technique based on fluorescent silica nanoparticles and bioorthogonal chemistries for the femtomolar detection of the HIV-1 p24 antigen. We developed a magnetic bead-based assay, wherein we used fluorescent-dye-encapsulated silica nanoparticles as reporters. The number of reporters was increased by using bioorthogonal chemistry to provide signal enhancement. The limit and range of detection of the sandwich immunoassay using alternating multiple layers for p24 in human serum were found to be 46 fg/mL (1.84 fM) and 46 fg/mL to 10 ng/mL, respectively. This simple assay was 217-fold higher in sensitivity compared to that of commercial enzyme-linked immunoassays (limit of detection of 10 pg/mL).

Colorimetric and photothermal dual-mode aptasensor with redox cycling amplification for the detection of ochratoxin A in corn samples

Ochratoxin A (OTA) detection is critical for public health safety. This study proposes a G-quadruplex-Hemin/iodide (G4-Hemin/I−)-mediated non-enzyme redox cycling amplification (RCA) system for dual-modal (colorimetric and photothermal thermometer) OTA analysis. The proposed aptasensor platform for point-of-care testing employs a common thermometer for quantitative signal readouts. The OTA aptamer folds into a G4 structure, which significantly enhances the catalytic activity in the presence of I− after RCA reaction. Moreover, a notable temperature enhancement causes color changes, providing an ultrasensitive and label-free platform for OTA detection. Further, the designed sensor was applied to OTA content determination in corn samples and achieved satisfactory results compared to a commercial enzyme-linked immunoassay kit. The proposed dual-mode aptasensor is simple, highly sensitive (1 pg/mL for colorimetric method, 0.8 pg/mL for photothermal method), selective, and suitable for low-cost instrument-free bioanalysis in low-resource settings.

Determining the Seroprevalence and the Knowledge of Viral Hepatitis B Infection among Beauticians in Yenagoa LGA, Yenagoa, Bayelsa State, Nigeria

Cosmetology is a rapidly growing field, resulting in increasing numbers of beauty centers and beauticians. Ear piercing is a common practice in Nigeria and, in recent years piercing of other body parts has greatly increased in popularity. Beauty treatments, such as piercing, tattooing, manicuring, and barbing are used by many people. Individuals working in barber shops, hairdressing and beauty centers are likely to have contact with blood through applications such as shaving, manicure, pedicure and skin care. The aim of this study was to determine hepatitis B virus (HBV) seroprevalence in a sample of beauticians in Yenagoa local government area, Bayelsa State (Nigeria) and to assess the level of knowledge of these professionals regarding viral hepatitis. This was a descriptive cross-sectional study involving a total of 120 beauticians (hairdressers and manicurists/pedicurists) that were selected by a multistage sampling method. Data was collected by an interviewer-administered questionnaire for knowledge assessment and serum samples were tested for HBsAg positivity using commercial enzyme-linked immunoassay (ELISA) kits. Data collected were analyzed using the statistical package for social science (SPSS), version 25 software. Of the total 120 participants 16 (13.3%) were males and 104 (86.7%) were females. The prevalence of HBV infections among the respondents was 7.5%. The knowledge of beauticians on awareness of viral hepatitis B was 5.8%, and their knowledge on ways of transmission was 61.7%. Conclusions: the findings indicate that, due to their low level of awareness of viral hepatitis B existence, beauticians working in Yenagoa Local Government Area are in a risk of HBV infection even though the seroprevalence of HBV was low.

An anti-fouling wearable molecular imprinting sensor based on semi-interpenetrating network hydrogel for the detection of tryptophan in sweat

The challenge of heavy biofouling in complex sweat environments limits the potential of electrochemical sweat sensors for noninvasive physiological assessment. In this study, a novel semi-interpenetrating hydrogel of PSBMA/PEDOT:PSS was engineered by interlacing PEDOT:PSS conductive polymer with zwitterionic PSBMA network. This versatile hydrogel served as the foundation for developing an anti-fouling wearable molecular imprinting sensor capable of sensitive and robust detection of tryptophan (Trp) in complex sweat. The incorporation of PEDOT:PSS conductive polymer into the semi-interpenetrating hydrogel introduced diverse physical crosslinks, including hydrogen bonding, electrostatic interactions, and chain entanglement. This incorporation considerably boosted the hydrogel's mechanical robustness and imparted commendable self-healing property. At the same time, the synergistic coupling between the well-balanced charge of the zwitterionic network and the high conductivity of the PEDOT:PSS polymer facilitated efficient charge transfer. The formation of the desired molecular imprinting membrane of semi-interpenetrating hydrogel was triggered by self-polymerization of dopamine (DA) in the presence of Trp. The designed biosensor demonstrated good sensitivity, selectivity and stability in detecting the target Trp. Notably, it also exhibited exceptional anti-fouling abilities, allowing for accurate Trp detection in complex real sweat samples, yielding results comparable to commercial enzyme-linked immunoassay (ELISA).

Impaired systemic nucleocapsid antigen clearance in severe COVID-19.

The circulating nucleocapsid (NCP) antigen of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is detectable in coronavirus disease-2019 (COVID-19) patients. To better understand the biology of disease severity, we investigated NCP clearance kinetics in hospitalized COVID-19 patients. Serum NCP was quantified using a commercial NCP-specific enzyme-linked immunoassay in hospitalized COVID-19 patients (n = 63) during their hospital stay. Results were correlated to COVID-19 disease severity, inflammation parameters, antibody response, and results of SARS-CoV-2 PCR from nasopharyngeal swabs. We demonstrate that NCP antigen levels in serum remained elevated in 21/45 (46.7%) samples from patients in intensive care units (ICU) after >8 days postdiagnosis. The proportion of ICU patients with detectable antigenemia declined only gradually from 84.6% to 25.0% over several weeks. This was in contrast to complete NCP clearance in all non-ICU patients after 8 days, and also in contrast to mucosal clearance of the virus as measured by PCR. Antigen clearance was associated with higher IgG against S1 but not NCP. Clearance of NCP antigenemia is delayed in >40% of severely ill COVID-19 patients. Thus, NCP antigenemia detected after 8 days post COVID-19 diagnosis is a characteristic of patients requiring intensive care. Prospective trials should further investigate NCP antigen clearance kinetics as a mechanistic biomarker.

P26-017-23 Comparing Plasma Phylloquinone Concentrations Measured Using Commercial Enzyme-linked Immunoassays to High Performance Liquid Chromatography

P26-017-23 Comparing Plasma Phylloquinone Concentrations Measured Using Commercial Enzyme-linked Immunoassays to High Performance Liquid Chromatography

Low serum level of 25-OH vitamin D relates to Th17 and treg changes in colorectal cancer patients.

BackgroundSerum 25‐hydroxyvitamin D [25(OH)D] level alters in colorectal cancer (CRC) development. Regulatory T (Treg) cells and T‐ helper type 17 (Th17) cells are involved in immune response. Th17‐mediated proinflammatory responses contribute to tumorigenesis, and Treg plays different roles in different periods of CRC. Vitamin D deficiency is associated with significant variations in peripheral immune cells. This study investigated the relationship between Th17 and Treg cells and 25(OH)D level in CRC.MethodsNinety‐five CRC patients were included, as well as 80 healthy controls during the same period at the Affiliated Hospital of Jiangnan University. 25(OH)D level was analyzed through electrochemiluminescence (ECLIA). Th17 and Treg levels were evaluated through flow cytometry. Serum levels of interleukin (IL)‐10, IL‐17, IL‐23, and transforming growth factor‐β (TGF‐β), were analyzed through commercial enzyme‐linked immunoassay (ELISA) kits.Results25(OH)D levels were downregulated in the serum of CRC patients. Decreased 25(OH)D level contributed to CRC pathogenesis. Decreased 25(OH)D level in CRC correlated with increased Treg and Th17 cell ratios and TGF‐β1, IL‐10, IL‐17, and IL‐23 levels in peripheral blood.ConclusionDecreased 25(OH)D level in the serum of CRC patients had negative correlation with Treg and Th17 ratios and relative cytokines levels.

Survey on the Presence of Equine Tick-Borne Rickettsial Infections in Southcentral United States

Although ticks are known vectors of pathogens across a range of hosts, there is limited research on emerging tick-borne diseases of horses in the United States. Tick surveys from other regions suggest Rickettsia spp. and Ehrlichia spp. may be clinically relevant in horses. To better understand the transmission risk of these tick-borne rickettsial disease agents to horses, ticks were collected from horses in Oklahoma. Ticks for the current study (306 Amblyomma americanum, 20 Dermacentor albipictus, 19 D. variabilis, and 7 A. maculatum) were evaluated for Rickettsia spp. and Ehrlichia spp. using polymerase chain reaction and sequence analysis. Serum samples from infested and noninfested horses were evaluated for antibodies to R. rickettsii using indirect fluorescence antibody testing and Ehrlichia spp. and Anaplasma spp. using a commercial enzyme-linked immunoassay. Of the horses with tick infestations, 71.4% hosted at least one tick with a rickettsial agent detected. Rickettsia spp. were identified in 25.9% (91/352) of the ticks tested with R. amblyommatis (80.2%; 73/91) most often detected. Ehrlichia spp. were identified in 2.8% (10/352) of the ticks tested with E. ewingii most often identified. Serologic screening revealed no horses with antibodies to R. rickettsii or Anaplasma spp., but 29.6% of the examined horses had circulating antibodies to Ehrlichia spp. Together, these results demonstrate the presence of Rickettsia spp. and Ehrlichia spp. in equine ticks and evidence of past or current infection with Ehrlichia spp. in Oklahoma horses which strongly suggests there is a need to explore the relationship between these agents and equine health.

A novel method for detection of ochratoxin A in foods—Co-MOFs based dual signal ratiometric electrochemical aptamer sensor coupled with DNA walker

Ochratoxin A (OTA) is a naturally occurring mycotoxin that poses serious threats, such as kidney damage, to human health. Therefore, we developed a DNA walker-based dual-signal electrochemical ratiometric platform for OTA detection, which could overlook the variations in environmental and instrumental factors and DNA load densities. Cobalt metal–organic frameworks (Co-MOFs) and toluidine blue were used as the electrochemical signal tag and internal reference probe, respectively. In the presence of OTA, this developed machine resulted in the DNA labelled-Co-MOFs far away from the electrode. Thus, Co-MOFs signal at −1.18 V decreased, while toluidine blue at −0.28 V increased. This proposed strategy has displayed superior sensitivity (limit of detection = 0.31 fg/mL, linear range = 1–50 ng/mL) and high reproducibility. The sensor was also applied for determining OTA content in red wine samples and the results were comparable to those of commercial enzyme-linked immunoassay kits with satisfactory results.

Tunable multiplexed fluorescence biosensing platform for simultaneous and selective detection of paraquat and carbendazim pesticides

The monitoring of multiple pesticides commonly used in food is a prerequisite for public health safety. Herein, a multiplexed biosensor based on fluorescence resonance energy transfer (FRET) from multicolor upconversion nanoparticles (UCNPs)to single black phosphorus nanosheets (BPNSs) was successfully developed for simultaneous and selective detection of paraquat and carbendazim pesticides. Due to the strong π-π stacking interactions, aptamers functionalized UCNPs may adsorb on the BPNSs surface, allowing strong upconversion fluorescence quenching. In the presence of paraquat and carbendazim, the aptamers preferentially integrated with their corresponding targets and altered the aptamer’s conformation, restoring the fluorescence. An excellent linear correlation was observed from 1.0 to 1.0 × 105 ng/mL, with a limit of detection of 0.18 ng/mL for paraquat and 0.45 ng/mL for carbendazim. The developed aptasensor was further validated by commercial enzyme-linked immunoassays without significant differences in practical detection. Additionally, this work offers new insights into monitoring multiple targets simultaneously.

Comparative performance of five recombinant and chimeric antigens in a time-resolved fluorescence immunoassay for detection of Toxoplasma gondii infection in cats

Felids are definitive hosts of Toxoplasma gondii, being the only hosts that can spread the infection through oocyst shedding in their feces. The elevated presence of this parasite in the domestic cat (Felis catus), and its close contact with humans, make it necessary to obtain reliable diagnostic methods to detect positive animals as a public health measure. For this reason, in this study, the diagnostic performance of five different recombinant antigen-based techniques was assessed to diagnose T. gondii infection in cat blood plasma samples. Specifically, four T. gondii recombinant antigens (GRA7, truncated GRA7, SAG2, and truncated SAG2) and a chimeric antigen (SAG1-GRA8) were used. A time-resolved fluorescence immunoassay (TRFIA) was developed for each antigen, and the results of each of these techniques were compared with those obtained by a commercial enzyme-linked immunoassay (ELISA) and a modified agglutination test (MAT) as reference techniques. The TRFIA based on SAG1-GRA8 antigen showed better discrimination between seropositive and seronegative cats (p < 0.001), as well as a better area under the curve (0.95), sensitivity (93.6%), and specificity (89.5%) values for the optimal cut-off, versus the other TRFIAs. In addition, SAG1-GRA8 TRFIA showed substantial agreement (kappa value = 0.78) and a moderate significant correlation (Spearman’s correlation: r = 0.62, p < 0.001) compared with the reference techniques. On the other hand, since plasma samples were obtained from 101 cats in Bangkok city and four of them were Neospora caninum seropositive by indirect immunofluorescence assay (IFAT), this is the first time that anti-N. caninum antibodies are detected in cats in Thailand. In conclusion, our study highlights that the TRFIA with TgSAG1-GRA8 antigen is an accurate and recommended diagnostic technique for detecting anti-T. gondii antibodies in cats.

Toward the calibration of serological assays using sera collected from cattle and sheep following a single dose of foot-and-mouth disease vaccine.

Background and Aim:Serological assays are widely used to monitor the performance of foot-and-mouth disease (FMD) vaccines to estimate vaccination coverage and to ensure that vaccinated animals generate adequate immune responses. This study aimed to measure the FMD virus (FMDV)-specific responses in cattle and sheep after a single dose of a trivalent FMD vaccine containing serotypes A, O, and Asia-1, and to use these sera to calibrate virus neutralization tests (VNTs) and serotype-specific serological enzyme-linked immunoassays (ELISAs) that can measure post-vaccination responses.Materials and Methods:Sera were collected from cattle (n=10) and sheep (n=10) on 0, 21, and 56 days after immunization with an imported aqueous formulated FMD vaccine. These samples were tested by VNT using field FMDV isolates that are representative of the epidemiological risks in Central Asia (A/ASIA/Iran-05, A/ASIA/GVII, O/ME-SA/Ind-2001, O/SEA/Mya-98, O/ME-SA/PanAsia, and Asia-1 Shamir). Heterologous VNT antibody responses were compared to those measured using commercial FMDV-specific ELISAs for serotypes O, A, and Asia 1.Results:Administration of the FMD vaccine increased FMDV-specific antibody titers for both species in sera collected on day 21, but these elevated titers were short-lived and were decreased by day 56.Conclusion:These results highlight the short duration of immunity with a single dose of this aqueous vaccine and motivate further studies to assess immune responses in cattle and small ruminants after a two-dose course vaccination schedule. Further comparative data for VNT and serotype-specific ELISAs are needed to define cutoffs that can be used to monitor post-vaccination immune responses in low-containment laboratories where it is not possible to handle live FMDVs.

Urinary CXCL10 specifically relates to HLA-DQ eplet mismatch load in kidney transplant recipients

BackgroundUrinary CXCL10 (uCXCL10) is associated with graft inflammation and graft survival, but the factors related to its excretion are not well known. HLA molecular matching at epitope level allow estimating the “dissimilarity” between donor and recipient HLA more precisely, being better related to further transplant outcomes. The relationship between uCXCL10 and HLA molecular mismatch has not been previously explored. MethodsHLA class I and class II typing of some 65 recipients and their donors was retrospectively performed by high resolution sequence-specific-primer (Life Technologies, Brown Deer, WI). The HLA-Matchmaker 3.1 software was used to assess eplet matching. Urine samples collected on the day of the 1-year surveillance biopsy were available of these 65 patients. uCXCL10 was measured using a commercial enzyme-linked immunoassay kit. Results1-year uCXCL10 was independently associated with HLA-DQB1 eplet mismatch load (β 0.300, 95%CI 0.010–0.058, p = 0.006). Kidney transplant recipients with a HLA-DQB1 eplet mismatch load >3 showed higher values of uCXCL10 at 1-year (p = 0.018) than those with ≤3. Patients with a HLA-DQB1 eplet mismatch load >3 with subclinical AbMR had significantly higher levels of the logarithm of 1-year uCXCL10 (No AbMR 0.88, IQR 0.37; AbMR 1.38, IQR 0.34, p = 0.002) than those without AbMR. ConclusionsuCXCL10 specifically relates to HLA-DQ eplet mismatch load. This relationship can partly explain the previously reported association between uCXCL10 excretion and graft inflammation. An adequate evaluation of any potential non-invasive biomarker, such as uCXCL10, must take into account the HLA molecular mismatch.

Prevalence and Genetic Diversity of Norovirus in Acute Gastroenteritis Cases in the Southwest Province of Turkey.

Aims:Noroviruses may cause both epidemic and sporadic acute gastroenteritis globally. Thus, this study evaluated the prevalence of norovirus in stool samples of hospitalized patients with acute gastroenteritis in Aydin, Turkey using enzyme-linked immunoassay (ELISA) and real-time reverse transcription-polymerase chain reaction (rRT-PCR) and genotyped positive samples to detect which genotypes have currently circulated.Methods:This retrospective descriptive study collected 92 stool samples from patients with acute gastroenteritis symptoms from Aydın Adnan Menderes University Hospital from September 2017 to May 2019. The samples were tested using the commercial Third Generation Ridascreen norovirus ELISA and rRT-PCR. Positive samples were genotyped by sequencing of conventional positive RT-PCR products followed by phylogenetic analysis.Results:Of the 92 samples, 5 (5.4%) using ELISA and 12 (13%) using rRT-PCR tested positive for norovirus. All positive samples were genogroup II (GII). Two norovirus positive samples were genotyped successfully using DNA sequencing of the nested conventional PCR products. One sample (GII/Hu/TR/2019/Aydin25) could be categorized as GII.3 and the other (GII/Hu/TR/2019/Aydin20) as GII.13.Conclusion:rRT-PCR testing of stool samples is more sensitive than Ridascreen ELISA. Data from our study provide protocols for how to study norovirus epidemiology.

Age-Related Value of Anti-Mullerian Hormone

Background: There is a correlation between anti-mullerian hormone (AMH) and the age when it becomes undetectable during menopause. The AMH immunoassay has been widely estimated in clinical practice to assist in reproduction and infertility treatment. Objective: To investigate the normal level of serum anti-mullerian hormone (AMH) in relation to women’s age in Basra. Patients and Methods: Cross-sectional study was carried out in Basra Maternity and Child Hospital from January 2018 to September 2019. Serum AMH levels were estimated for 975 women aged 15–50 years. They were classified into 7 age groups:15–20, 20–25, 25–30, 30–35, 35–40, 40–45 and 45–50 years. Serum AMH and FSH levels were determined by commercial enzyme-linked immunoassay. Results: Negative relationship was noticed between AMH concentration and age. The mean AMH levels for the age groups 1, 2, 3, 4, 5, 6 and 7 were 4.9 ng/ml, 4.25ng/ml, 3.27 ng/ml, 2.43ng/ml, 2.17ng/ml, 1.95ng/ml and 0.9ng/ml respectively. Conclusions: This study recorded normal levels of AMH in women in Basra. These levels can be considered for the medical treatment of infertile women. Keywords: age, anti-mullerian hormone, FSH.

Elevated Plasma X-Linked Neuroligin 4 Expression Is Associated with Autism Spectrum Disorder

Objectives: In this study, we compared plasma levels of neuroligin 4 (NLGN4) in children with autism versus matched healthy controls to examine a possible correlation between plasma NLGN4 and degree of autism severity as well as social impairment in autistic patients. Subjects and Methods: 88 autistic patients aged 3–12 years and 33 age- and sex-matched controls aged 3–9 years were recruited. Plasma levels of NLGN4 were determined using a commercial enzyme-linked immunoassay (ELISA). The Childhood Autism Rating Scale (CARS) and the Social Responsiveness Scale (SRS) were used to assess cognitive dysfunction and social impairment in autistic patients. Results: Plasma levels of NLGN4 were significantly higher (p = 0.001) in autistic children than in healthy controls. Despite alterations in the levels of NLGN4 in the subgroups of the autistic children, no correlation between plasma concentration of NLGN4 and cognitive problems or social impairment was observed (p> 0.05). Conclusion: Increased plasma concentrations of NLGN4 may play a role in the pathogenesis of autism, and it could be a valuable biomarker for autism. Further studies with larger sample sizes are warranted to validate this finding and also to explore the potential links between NLGN4 and the features of autism.

Effect of Coagulation Factor Concentrates on Markers of Endothelial Cell Damage in Experimental Hemorrhagic Shock.

Plasma-based resuscitation showed protective effects on the endothelial glycocalyx compared with crystalloid resuscitation. There is paucity of data regarding the effect of coagulation factor concentrates (CFC) on the glycocalyx in hemorrhagic shock (HS). We hypothesized that colloid-based resuscitation supplemented with CFCs offers a therapeutic value to treat endothelial damage following HS. Eighty-four rats were subjected to pressure-controlled (mean arterial pressure (MAP) 30-35 mm Hg) and lab-guided (targeted cutoff: lactate >2.2. mmol/L and base deficit > 5.5 mmol/L) HS. Animals were resuscitated with fresh frozen plasma (FFP), human albumin (HA) or Ringer's lactate (RL) and RL or HA supplemented with fibrinogen concentrate (FC) or prothrombin complex concentrate (PCC). Serum epinephrine and the following markers of endothelial damage were assessed at baseline and at the end-of-observation (120 min after shock was terminated): syndecan-1, heparan sulfate, and soluble vascular endothelial growth factor receptor 1 (sVEGFR 1). Resuscitation with FFP had no effect on sVEGFR1 compared with crystalloid-based resuscitation (FFP: 19.3 ng/mL vs. RL: 15.9 ng/mL; RL+FC: 19.7 ng/mL; RL+PCC: 18.9 ng/mL; n.s.). At the end-of-observation, syndecan-1 was similar among all groups. Interestingly, HA+FC treated animals displayed the highest syndecan-1 concentration (12.07 ng/mL). Resuscitation with FFP restored heparan sulfate back to baseline (baseline: 36 ng/mL vs. end-of-observation: 36 ng/mL). The current study revealed that plasma-based resuscitation normalized circulating heparan sulfate but not syndecan-1. Co-administration of CFC had no further effect on glycocalyx shedding suggesting a lack of its therapeutic potential. VExperimental in vivo study.

642. Higher Diagnostic Accuracy with Ultrasensitive Detection of Helicobacter pylori Stool Antigen Using Single-Molecule Counting Technology

BackgroundCurrent diagnostic methods for Helicobacter pylori infection include fecal antigen tests, 13C-urea breath test, and gastric biopsy. The breath test is limited by poor specificity and the fecal antigen tests by poor sensitivity. We have developed a prototype assay for detection of H. pylori antigen in human stool, powered by ultrasensitive Single Molecule Counting technology, and compared the analytical performance to a commercially available enzyme-linked immunoassay (EIA) antigen test.MethodsThe Singulex Clarity H. pylori antigen assay incubates diluted stool with capture and fluorescent-labeled detection antibodies. After incubation and wash steps, fluorescent molecules are eluted and single-molecule fluorescence measured by detected events (DE′). Analytical performance was compared with a commercial EIA (Premier Platinum HpSA® Plus, Meridian Bioscience, Inc.) using serial dilutions of H. pylori control (~37,500–1.7 ng/mL) and high positive stool (signal to noise ratio >2). Clinical performance was evaluated using two cohorts, one had 10 EIA-negative and 10 EIA-positive samples and the other 13 high positives (> 0.500 at 450/630) and 5 low positives near the EIA cutoff (0.100–0.500 at 450/630). One sample was excluded due to discordant EIA results, and three to reader flags.ResultsThe lower limit of detection of the Clarity H. pylori assay was 1.7 ng/mL and the EIA 1,250 ng/mL (IFU: LOD 4.67 ng/mL). A high positive stool sample was detectable by the Clarity H. pylori assay diluted 1:10,000,000 and by the EIA 1:10,000. The Clarity H. pylori assay showed a 729-fold increase in lower limit of detection and 1,000-fold increase in endogenous antigen lower limit of detection compared with the EIA. Clarity signal ranged from 46–665 DE’ for EIA-negative samples and 487,484–576,747 DE’ for EIA-positive samples.ConclusionThe Singulex Clarity H. pylori antigen assay may have orders of magnitude higher analytical sensitivity than the commercial EIA and demonstrated 100% positive agreement and 100% negative agreement on detection of H. pylori antigen in human stool samples. The ultrasensitive Clarity H. pylori assay has the potential for high sensitivity and specificity to improve current diagnostic options for H. pylori infection; however, additional multicenter studies are required.Disclosures All authors: No reported disclosures.

Diagnostic performance of commercial IgM and IgG enzyme-linked immunoassays (ELISAs) for diagnosis of Zika virus infection

BackgroundSerologic detection of Zika virus (ZIKV) infections is challenging because of antigenic similarities among flaviviruses.ObjectiveTo evaluate the sensitivity and specificity of commercial ZIKV IgM and IgG enzyme-linked immunoassay (ELISA) kits.MethodsWe used sera from febrile patients with RT-PCR-confirmed ZIKV infection to determine sensitivity and sera from RT-PCR-confirmed dengue cases and blood donors, both of which were collected before ZIKV epidemics in Brazil (2009–2011 and 2013, respectively) to determine specificity.ResultsThe ZIKV IgM-ELISA positivity among RT-PCR ZIKV confirmed cases was 0.0% (0/14) and 12.5% (1/8) for acute- and convalescent-phase sera, respectively, while its specificity was 100.0% (58/58) and 98.3% (58/59) for acute- and convalescent-phase sera of dengue patients, and 100.0% (23/23) for blood donors. The ZIKV IgG-ELISA sensitivity was 100.0% (6/6) on convalescent-phase sera from RT-PCR confirmed ZIKV patients, while its specificity was 27.3% (15/55) on convalescent-phase sera from dengue patients and 45.0% (9/20) on blood donors’ sera. The ZIKV IgG-ELISA specificity among dengue confirmed cases was much greater among patients with primary dengue (92.3%; 12/13), compared to secondary dengue (7.1%; 3/42).ConclusionsIn a setting of endemic dengue transmission, the ZIKV IgM-ELISA had high specificity, but poor sensitivity. In contrast, the ZIKV IgG-ELISA showed low specificity, particularly for patients previously exposed to dengue infections. This suggests that this ZIKV IgM-ELISA is not useful in confirming a diagnosis of ZIKV infection in suspected patients, whereas the IgG-ELISA is more suitable for ZIKV diagnosis among travelers, who reside in areas free of flavivirus transmission, rather than for serosurveys in dengue-endemic areas.