Developments in the HCV Screening Technologies Based on the Detection of Antigens and Antibodies

From viruses to cancer: exploring the role of the hepatitis C virus NS3 protein in carcinogenesis

Hepatitis C virus (HCV) chronically infects approximately 170 million people worldwide and is a known etiological agent of hepatocellular carcinoma (HCC). The molecular mechanisms of HCV-mediated carcinogenesis are not fully understood. This review article focuses on the oncogenic potential of NS3, a viral protein with transformative effects on cells, although the precise mechanisms remain elusive. Unlike the more extensively studied Core and NS5A proteins, NS3's roles in cancer development are less defined but critical. Research indicates that NS3 is implicated in several carcinogenic processes such as proliferative signaling, cell death resistance, genomic instability and mutations, invasion and metastasis, tumor-related inflammation, immune evasion, and replicative immortality. Understanding the direct impact of viral proteins such as NS3 on cellular transformation is crucial for elucidating HCV's role in HCC development. Overall, this review sheds light on the molecular mechanisms used by NS3 to contribute to hepatocarcinogenesis, and highlights its significance in the context of HCV-associated HCC, underscoring the need for further investigation into its specific molecular and cellular actions.

Contemporary Insights into Hepatitis C Virus: A Comprehensive Review

Hepatitis C virus (HCV) remains a significant global health challenge. Approximately 50 million people were living with chronic hepatitis C based on the World Health Organization as of 2024, contributing extensively to global morbidity and mortality. The advent and approval of several direct-acting antiviral (DAA) regimens significantly improved HCV treatment, offering potentially high rates of cure for chronic hepatitis C. However, the promising aim of eventual HCV eradication remains challenging. Key challenges include the variability in DAA access across different regions, slightly variable response rates to DAAs across diverse patient populations and HCV genotypes/subtypes, and the emergence of resistance-associated substitutions (RASs), potentially conferring resistance to DAAs. Therefore, periodic reassessment of current HCV knowledge is needed. An up-to-date review on HCV is also necessitated based on the observed shifts in HCV epidemiological trends, continuous development and approval of therapeutic strategies, and changes in public health policies. Thus, the current comprehensive review aimed to integrate the latest knowledge on the epidemiology, pathophysiology, diagnostic approaches, treatment options and preventive strategies for HCV, with a particular focus on the current challenges associated with RASs and ongoing efforts in vaccine development. This review sought to provide healthcare professionals, researchers, and policymakers with the necessary insights to address the HCV burden more effectively. We aimed to highlight the progress made in managing and preventing HCV infection and to highlight the persistent barriers challenging the prevention of HCV infection. The overarching goal was to align with global health objectives towards reducing the burden of chronic hepatitis, aiming for its eventual elimination as a public health threat by 2030.

A potential new way to facilitate HCV elimination: The prediction of viremia in anti-HCV seropositive patients using machine learning algorithms

BACKGROUND AND STUDY AIMS

The present study was undertaken to design a new machine learning (ML) model that can predict the presence of viremia in hepatitis C virus (HCV) antibody (anti-HCV) seropositive cases.

PATIENTS AND METHODS

This retrospective study was conducted between January 2012-January 2022 with 812 patients who were referred for anti-HCV positivity and were examined for HCV ribonucleic acid (HCV RNA). Models were constructed with 11 features with a predictor (presence and absence of viremia) to predict HCV viremia. To build an optimal model, this current study also examined and compared the three classifier data mining approaches: RF, SVM and XGBoost.

RESULTS

The highest performance was achieved with XGBoost (90%), which was followed by RF (89%), SVM Linear (85%) and SVM Radial (83%) algorithms, respectively. The four most important key features contributing to the models were: alanine aminotransferase (ALT), aspartate aminotransferase (AST), albumin (ALB) and anti-HCV levels, respectively, while "ALB" was replaced by the "AGE" only in the XGBoost model.

CONCLUSION

This study has shown that XGBoost and RF based ML models, incorporating anti-HCV levels and routine laboratory tests (ALT, AST, ALB), and age are capable of providing HCV viremia diagnosis with 90% and 89% accuracy, respectively. These findings highlight the potential of ML models in the early diagnosis of HCV viremia, which may be helpful in optimizing HCV elimination programs.

Establishment and methodological evaluation of a chemiluminescence assay for detection of anti-envelope protein (E1, E2) antibodies in the serum of hepatitis C virus-infected patients

BACKGROUND

To establish a chemiluminescence method for detecting anti-E1 and anti-E2 antibodies in the serum of patients with hepatitis C virus (HCV) infection.

METHODS

The microplate was coated with recombinant envelope proteins E1 and E2 by indirect method, respectively, and the kits for detecting anti-E1 and anti-E2 antibodies were prepared. The methodological indexes were evaluated.

RESULTS

The methodological indexes of the kits were as follows: precision test (the variation coefficient of anti-E1 antibody 6.71%-8.95% for within run and 9.91%-12.16% for between run, the variation coefficient of anti-E2 antibody 6.06%-8.44% for within run and 10.77%-13.98% for between run, respectively). The blank limit and detection limit were 1.18 RLIR and 3.16 RLIR for the anti-E1 antibody, and 1.26 RLIR and 3.32 RLIR for the anti-E2 antibody, respectively. The correlation coefficients (r) of anti-E1 and anti-E2 were 0.9963 and 0.9828, the analysis and measurement ranges (AMR) were 1.66-41.28 RLIR and 1.55-19.46 RLIR, and the average recovery was 96.4% and 93.7%, respectively. The rheumatoid factor and other positive serum samples had no interference or cross-reaction to the test, and the kits were stable within 15 months. The positive rates of anti-E1 and anti-E2 antibodies in 45 patients with HCV infection were 35.6% (16/45) and 44.4% (20/45), respectively.

CONCLUSIONS

The kits for detecting anti-E1 and anti-E2 meet the requirements of methodology, and can be used in screening diagnosis, disease monitoring, prognosis evaluation, disease mechanism, and epidemiological studies of HCV infection. The HCV envelope proteins E1 and E2 have an immune response in HCV-infected patients.

A new double-antigen sandwich test based on the light-initiated chemiluminescent assay for detecting anti-hepatitis C virus antibodies with high sensitivity and specificity

Objectives

The aim of this study was to evaluate the performance of a new double-antigen sandwich test that is based on the light-initiated chemiluminescent assay (LiCA®) for detecting anti-hepatitis C virus antibodies (anti-HCV) in comparison to Architect®.

Methods

Analytical characteristics and diagnostic performance were tested using seroconversion panels and large pools of clinical samples. Positive results were validated by the strip immunoblot assay (RIBA) and HCV RNA.

Results

Repeatability and within-lab imprecision of LiCA® anti-HCV were 1.31%-3.27%. The C5-C95 interval was -5.44%-5.03% away from C50. LiCA® detected seroconversion in an average of 28.9 days and showed a mean of 3.7 (p = 0.0056) days earlier than Architect®. In a pool of 239 samples with known HCV genotypes 1 to 6, both assays correctly detected all subjects. In 16,305 clinical patient sera, LiCA® detected 4 false-negative (0.25‰) and 14 false-positive (0.86‰) anti-HCV cases, while Architect® recorded 6 false-negative (0.37‰) and 138 false-positive (8.46‰) subjects, respectively. Compared to Architect®, LiCA® presented a significantly better performance in specificity (99.91% vs. 99.14%, n = 16,018, p < 0.0001), positive predictive value (95.29% vs. 67.06%, n = 419, p < 0.0001), and overall accuracy (99.89% vs. 99.12%, n = 16,305, p < 0.0001), while no significant difference in sensitivity (98.61% vs. 97.91%, n = 287, p = 0.5217) and negative predictive value (99.98% vs. 99.96%, n = 15,886, p = 0.3021) was seen. An S/Co value of 3.28 was predicted to be the threshold with a positivity ≥95% for the LiCA® anti-HCV assay.

Conclusion

LiCA® anti-HCV is a precise and fully automatic chemiluminescent assay with superior sensitivity and specificity. The assay can be used as a valuable tool to supplement the diagnosis of HCV infection.

Establishment and Evaluation of Recombinant Expression of HCV Transmembrane Protein (p7) and Detection of Anti-p7 Antibody in Serum of HCV-Infected Patients by Chemiluminescence

Objective

Our aim was to establish a chemiluminescence method for detecting anti-transmembrane protein (p7) antibody in the serum of patients with hepatitis C virus (HCV) infection.

Methods

The p7 gene was amplified by polymerase chain reaction using the plasmid PUC-p7 containing the p7 nucleic acid sequence of the HCV 1b genotype as the template, and recombinant plasmid pGEX-KG-p7 was constructed. After p7 fusion, the protein was induced and expressed in the prokaryote, extracted, and purified; the anti-p7 antibody detection kit was prepared, and its efficacy was evaluated.

Results

The plasmid pGEX-KG-p7 was constructed correctly, and p7 fusion protein was obtained. The methodological indexes of the kit, the precision test, blank limit and detection limit, etc, met the requirements. The positive rate of serum anti-p7 antibody in 45 patients with HCV infection was 20%.

Conclusions

The kit can be used in screening diagnosis, condition monitoring, prognosis, and disease mechanism and epidemiological study of HCV infection. The p7 protein has immune response in HCV-infected patients.

RT-LAMP-Based Molecular Diagnostic Set-Up for Rapid Hepatitis C Virus Testing

Hepatitis C virus (HCV) infections occur in approximately 3% of the world population. The development of an enhanced and extensive-scale screening is required to accomplish the World Health Organization's (WHO) goal of eliminating HCV as a public health problem by 2030. However, standard testing methods are time-consuming, expensive, and challenging to deploy in remote and underdeveloped areas. Therefore, a cost-effective, rapid, and accurate point-of-care (POC) diagnostic test is needed to properly manage the disease and reduce the economic burden caused by high case numbers. Herein, we present a fully automated reverse-transcription loop-mediated isothermal amplification (RT-LAMP)-based molecular diagnostic set-up for rapid HCV detection. The set-up consists of an automated disposable microfluidic chip, a small surface heater, and a reusable magnetic actuation platform. The microfluidic chip contains multiple chambers in which the plasma sample is processed. The system utilizes SYBR green dye to detect the amplification product with the naked eye. The efficiency of the microfluidic chip was tested with human plasma samples spiked with HCV virions, and the limit of detection observed was 500 virions/mL within 45 min. The entire virus detection process was executed inside a uniquely designed, inexpensive, disposable, and self-driven microfluidic chip with high sensitivity and specificity.

Revolution in the diagnosis and management of hepatitis C virus infection in current era

Chronic hepatitis C virus (HCV) infection is a major global public health problem, particularly in developing part of the world. Significant advances have been made in the early diagnosis and treatment of the disease. Its management has been particularly revolutionized during the past two decades. In this review, we summarize the major advances in the diagnostic and management armamentarium for chronic HCV infection. The focus of the present review is on the newer directly acting anti-viral agents, which have revolutionized the management of chronic HCV infection. Management of uncomplicated chronic HCV infection and of specific complications and special at-risk populations of patients will be covered in detail. Despite the advent and approval of highly effective and well tolerable oral agents, still many challenges remain, particularly the affordability, the equitable distribution and access to later drugs. The World Health Organization aims to eliminate viral hepatitis including HCV by 2030 since its poses a major public health threat. There is an urgent need to ensure uniform and early access to diagnostic and therapeutic facilities throughout the world if the later goal has to be realized.

Prevalence, diagnosis, and treatment of hepatitis C in Mainland China

Infection with the hepatitis C virus (HCV) is a major cause of liver disease and hepatocellular carcinoma in China. Rapid economic development has had an enormous impact on the epidemiology and treatment of hepatitis C. The prevalence of anti-HCV antibodies in Mainland China is approximately 0.91%, and use of injected drugs has become the main route of HCV transmission in China. Reimbursement for 3 direct-acting antivirals (DAAs) has been approved by the National Medical Insurance scheme in China, which ensures the accessibility of treatment for an HCV infection. To improve the awareness of treatments for hepatitis C among medical personnel and the rate of in-hospital screening for HCV, the Chinese Medical Association has formulated guidelines for the diagnosis and treatment of hepatitis C and a process of in-hospital screening for hepatitis C in China. These efforts have standardized the screening, diagnosis, treatment, and management of hepatitis C. Based on the international strategy for micro-elimination of hepatitis C, China has also screened and treated groups at risk of hepatitis C infection, and this has reduced the number of the infected. The current review describes the status of and issues with the prevalence, diagnosis, and treatment of hepatitis C in Mainland China as part of the global effort to eliminate viral hepatitis by 2030.

Hepatitis C Diagnosis: Simplified Solutions, Predictive Barriers, and Future Promises

The simplification of current hepatitis C diagnostic algorithms and the emergence of digital diagnostic devices will be very crucial to achieving the WHO's set goals of hepatitis C diagnosis (i.e., 90%) by 2030. From the last decade, hepatitis C diagnosis has been revolutionized by the advent and approval of state-of-the-art HCV diagnostic platforms which have been efficiently implemented in high-risk HCV populations in developed nations as well as in some low-to-middle income countries (LMICs) to identify millions of undiagnosed hepatitis C-infected individuals. Point-of-care (POC) rapid diagnostic tests (RDTs; POC-RDTs), RNA reflex testing, hepatitis C self-test assays, and dried blood spot (DBS) sample analysis have been proven their diagnostic worth in real-world clinical experiences both at centralized and decentralized diagnostic settings, in mass hepatitis C screening campaigns, and hard-to-reach aboriginal hepatitis C populations in remote areas. The present review article overviews the significance of current and emerging hepatitis C diagnostic packages to subvert the public health care burden of this 'silent epidemic' worldwide. We also highlight the challenges that remain to be met about the affordability, accessibility, and health system-related barriers to overcome while modulating the hepatitis C care cascade to adopt a 'test and treat' strategy for every hepatitis C-affected individual. We also elaborate some key measures and strategies in terms of policy and progress to be part of hepatitis C care plans to effectively link diagnosis to care cascade for rapid treatment uptake and, consequently, hepatitis C cure.

A study based on four immunoassays: Hepatitis C virus antibody against different antigens may have unequal contributions to detection

Background

All commercial Hepatitis C virus antibody (anti-HCV) assays use a combination of recombinant antigens to detect antibody response. Antibody responses to individual antigenic regions (core, NS3/4 and NS5) used in assays have not been investigated.

Methods

In this study, we quantified HCV viral load, tested anti-HCV with four commercial assays (Ortho-ELISA, Murex-ELISA, Architect-CMIA and Elecsys-ECLIA) in 682 plasma specimens. In antigenic region ELISA platform, microwells were coated with three antigens: core (c22-3), NS3/4 (c200) and NS5 individually. The signal-to-cutoff (S/Co) values of different assays, and antibody responses to individual antigens were compared. The specimens were divided into HCV RNA positive group, anti-HCV consistent group, and anti-HCV discrepant group.

Results

Anti-core and anti-NS3/4 were simultaneously detected in 99.2% of HCV RNA positive specimens and showed great consistency with total anti-HCV signals. Responses to the core region were more robust than those to the NS3/4 region in anti-HCV consistent group (p < 0.001). Anti-NS5 only occurred in companying with responses to the core and NS3/4 antigens, and failed to affect the final anti-HCV positive signals. In anti-HCV discrepant group, 39.0% of positive signals could not be traced back to any single antigenic region.

Conclusion

Antibody responses to the core and NS3/4 antigens were stronger, whereas responses to the NS5 antigen were the weakest, indicating that individual antigenic regions played different roles in total anti-HCV signals. This study provides an impetus for optimizing commercial anti-HCV assays.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12985-021-01608-x.

Evaluation of seven rapid diagnostic tests for detection of hepatitis C virus antibodies in China

Rapid diagnostic tests as an attractive alternative to enzyme immunoassay could identify hepatitis C virus (HCV) infected persons more expeditiously. The availability of high performing and quality-assured rapid diagnostic tests are essential to scale-up HCV screening. The study was undertaken to evaluate the performance of seven domestic HCV rapid diagnostic tests kits. The kits were evaluated by using HCV serum panels, including HCV basic panel, analytical specificity panel, mixed titre performance panel, characteristic panel, seroconversion panel, and genotype qualification panel. The results showed that clinical sensitivity, clinical specificity and analytical specificity of seven rapid diagnostic tests kits ranged from 94% (95% CI: 83.2-98.6) to 100% (95% CI: 91.5-100). Furthermore, specimens with HCV genotypes 1b, 2a, 3a, 4a, 5a, 6 could be detected by HCV rapid diagnostic tests kits, whereas specimens with genotypes 1a and 2b could not be detected. Additionally, most HCV rapid diagnostic tests kits had great performance in diagnosing different titres and/or different bands samples, but some low S/CO value specimens may not be fully detected by few rapid diagnostic test kits. In conclusion, seven HCV rapid diagnostic tests reagents presented high sensitivity, specificity, good anti-interference and detection ability of early infection, which could meet the requirements of clinical HCV antibody screening.

Hepatitis C virus (HCV) diagnosis via microfluidics

Humans are subjected to various diseases; hence, proper diagnosis helps avoid further disease consequences. One such severe issue that could cause significant damage to the human liver is the hepatitis C virus (HCV). Several techniques are available to detect HCV under various categories, such as detection through antibodies, antigens, and RNA. Although immunoassays play a significant role in discovering hepatitis viruses, there is a need for point-of-care tests (POCT). Some developing strategies are required to ensure the appropriate selection of POCT for HCV detection, initiate appropriate antiviral therapy, and define associated risks, which will be critical in achieving optimal outcomes. Though molecular assays are precise, reproducible, sensitive, and specific, alternative strategies are required to enhance HCV diagnosis among the infected population. Herein, we described and assessed the potential of various microfluidic detection techniques and confirmatory approaches used in present communities. In addition, current key market players in HCV chip-based diagnosis and the future perspectives on the basis of which the diagnosis can be made easier are presented in the present review.

Comparison of double antigen sandwich and indirect enzyme-linked immunosorbent assay for the diagnosis of hepatitis C virus antibodies

BACKGROUND

The aim of this study is to compare double-antigen sandwich enzyme-linked immunosorbent assay (ELISA) and indirect ELISA in the diagnosis of hepatitis C virus（HCV）infection.

METHODS AND MATERIALS

A total of 176 samples from the Tumor Hospital Affiliated to Xin Jiang Medical University were utilized to comparison. All serum samples were tested using double-antigen sandwich ELISA and indirect ELISA. Cohen's kappa statistics were used to assess the agreement between the two assays, and multivariate analysis was used to evaluate risk factors for the discordance between the double-antigen ELISA and indirect ELISA.

RESULTS

The positivities of indirect ELISA (Beijing Wantai), double-antigen sandwich ELISA (Beijing Wantai), and indirect ELISA (Beijing Jinhao) were 74.43%, 68.75%, and 73.30%, respectively. The agreement between the indirect ELISA (Beijing Wantai) and double-antigen sandwich ELISA (Beijing Wantai) was high (κ = 0.829;P < .001), and the agreement between the double-antigen sandwich ELISA (Beijing Wantai) and indirect ELISA (Beijing Jinhao) was high (κ = 0.847;P < .001). Variables associated with discordant results between the double-antigen sandwich and indirect ELISA in multivariate analysis were as follows: female (OR:1.462; P < .05), age (<35 years old; OR:3.667; P < .05), and cancer (suffer from malignant tumor; OR:3.621; P < .05).

CONCLUSION

In detection of HCV, high agreement was found between the double-antigen sandwich ELISA and indirect ELISA. Female, younger age, and suffer from malignant tumor were significant risk factors for the discordance. Based on double-antigen sandwich ELISA has distinct methodological advantages over indirect ELISA. It is recommended for the diagnosis of HCV infection.

Evaluation of a Novel Enzyme-Linked Immuno Assay Model to Detect E2 Antigen and Antibodies Against Core, NS3, NS4, and NS5 Antigens of Hepatitis C Virus

Background: The serological measurement of the anti‐hepatitis C virus antibody is a widely used tool in the first-line diagnosis of HCV infection. Therefore, increasing the testing criteria of these tests is of crucial importance for screening HCV infection. Objectives: The current study aimed to optimize a novel enzyme-linked immuno assay model to detect E2 antigen with or without sample pretreatment in combination with antibodies against core, NS3, NS4, and NS5 antigens of the hepatitis C virus and to compare the performances of these assays with indirect antigen (Ag), biotin/HRP labeled Antigen Sandwich and methods of enzyme-linked immunosorbent assay (ELISA) for their ability to detect HCV. Methods: A total of 107 positive and 415 negative controls from volunteer whole blood donors in Blood Transfusion Organization and 204 blood samples from patients under hemodialysis treatment in Tehran and Bandar Abbas hemodialysis centers are investigated. Six different methods of ELISA test were used to detect anti-HCV antibodies and/or HCV antigens in serum samples. Results: Regarding sensitivity, specificity, and accuracy, E2 Antigen detection alone or combined with antibody detection have the highest accuracy value (99% and 98%, respectively) compared to other methods for antibodies detection. The results of the combined Ag/Ab ELISA test were closer to the results of real-time PCR. Conclusions: This new approach to the detection of antigen and antigen/antibody has better performance criteria concerning the serologic detection of HCV, especially in HD patients who might experience a longer window period.

Comparison of serologic and molecular SARS-CoV 2 results in a large cohort in Southern Tuscany demonstrates a role for serologic testing to increase diagnostic sensitivity

Background

Since February 2020, Italian hospitals registered COVID-19 (COronaVIrus Disease 19) cases more often than the rest of the Europe. During this epidemic, health authorities requested swab tests, while seeking new patient paths.

Methods

A dual laboratory approach was evaluated, consisting of patient care reports for viral RNA detection on swabs and rapid serological tests in 516 patients (192 symptomatic or paucisymptomatic and 324 asymptomatic).

Results

We found the molecular positive fraction equal to 12% (23/192) among symptomatic/paucisymptomatic (S/P) and 15.4% (50/324) in asymptomatic (As) sets. Among subsets, we observed serologically positive results, corresponding to 35% (8/23) for S/P and 38% (19/50) for As. Among molecular negative cases, we detected specific Immunoglobulin G or M (Ig G or Ig M) positivity in the S/P cohort equal to 6.6% (11/167) and 6% (15/246) in As cases. For indeterminate molecular results, we found S/P serological positivity equal to 100% (1/1) and 54% (13/24) in As patients. We found higher (p < 0.05) seropositivity in older patients (n = 8) among symptomatic and positives for viral RNA (n.23).

Conclusions

It has been observed that a dual approach of serological and molecular tests detects a higher absolute number of disease cases in a pandemic context,which could improve monitoring and health surveillance efficacy. The age-related seropositivity frequency in this study, if confirmed, could enhance the validity of serological tests, especially in older patients.In these subjects, molecular positivity accompanied by serological positivity (distinct for M and G immunoglobulins) should help determine disease status and support decisions related to patient management.

Towards the Development of a 3-D Biochip for the Detection of Hepatitis C Virus

The early diagnostics of hepatitis C virus (HCV) infections is currently one of the most highly demanded medical tasks. This study is devoted to the development of biochips (microarrays) that can be applied for the detection of HCV. The analytical platforms of suggested devices were based on macroporous poly(glycidyl methacrylate-co-di(ethylene glycol) dimethacrylate) monolithic material. The biochips were obtained by the covalent immobilization of specific probes spotted onto the surface of macroporous monolithic platforms. Using the developed biochips, different variants of bioassay were investigated. This study was carried out using hepatitis C virus-mimetic particles (VMPs) representing polymer nanoparticles with a size close to HCV and bearing surface virus antigen (E2 protein). At the first step, the main parameters of bioassay were optimized. Additionally, the dissociation constants were calculated for the pairs “ligand–receptor” and “antigen–antibody” formed at the surface of biochips. As a result of this study, the analysis of VMPs in model buffer solution and human blood plasma was carried out in a format of direct and “sandwich” approaches. It was found that bioassay efficacy appeared to be similar for both the model medium and real biological fluid. Finally, limit of detection (LOD), limit of quantification (LOQ), spot-to-spot and biochip-to-biochip reproducibility for the developed systems were evaluated.

Does a change in quality control results influence the sensitivity of an anti-HCV test?

Background

Laboratories use quality control (QC) testing to monitor the extent of normal variation. Assay lot number changes contribute the greatest amount of variation in infectious disease serology testing. An unexpected change in six lots of an anti-HCV assay allowed the determination of the effect these lot changes made to the assay’s clinical sensitivity.

Methods

Two sets of seroconversion samples comprising of 44 individual samples and 9 external quality assessment scheme (EQAS) samples, all positive to anti-HCV, were tested in affected and unaffected assay lots, and the difference in the quantitative and qualitative results of the samples was analyzed.

Results

Of 44 low-positive seroconversion samples tested in affected and unaffected assay lots, only three samples had results reported below the assay cutoff when tested on two of the six affected assay lot. A further sample had results below the cutoff for only one affected lot. None of the EQAS samples reported false-negative results. Samples having a signal to cutoff value of less than 6.0 generally had lower results in the affected lots compared with the unaffected lots.

Conclusions

Unexpected changes in QC reactivity related to variation, in particular assay lot changes, may affect patient results. This study demonstrated that QConnect Limits facilitated the detection of an unexpectedly large variation in QC test results, allowed for the identification of the root cause of the change, and showed that the risk associated with the change was low but credible. The use of evidence-based QC program is essential to detect changes in test systems.