Serological diagnostic for SARS-CoV-2: an experimental External Quality Assessment Scheme

Objectives Numerous analytical systems, rapidly made available on the market throughout the SARS-CoV-2 pandemic, aim to detect COVID-19, and to continuously update and improve the same systems. Medical laboratory professionals have also developed in-house analytical procedures in order to satisfy the enormous volume of requests for tests. These developments have highlighted the need control the analytical procedures used in order to guarantee patient safety. The External Quality Assessment (EQA) Scheme, an important quality assurance tool, aims to guarantee high standard performance for laboratory and analytical procedures. The aim of the present study was to report on the results collected in an experimental EQA scheme for the serological diagnosis of SARS-CoV-2. Methods All qualitative results collected in the different EQA surveys were summarized in order to identify the percentage of laboratory results in relation to typology of antibodies, results and samples. Results A total of 4,867 data sets were collected. The analysis of EQA data made, demonstrates a better agreement among laboratories results for total Ig than single immunoglobulins (IgG, IgM, IgA) in the case samples positive for SARS-CoV-2, and a wide divergence between IgM results for positive samples (only 34.9% were correct). Results for negative controls and specificity controls demonstrated a better overall agreement than results for positive samples. Conclusions Working in collaboration with the IVD manufacturers, laboratory professionals must strive to achieve harmonization of results, and to develop well-defined protocols complying with the ISO 15189 requirements.

The assessment of microbiological diagnostics’ credibility in Poland on the basis of the POLMICRO 2019 Program results

Introduction: This article describes the course and results of the 26th edition of the Polish National External Quality Assessment Scheme in Microbiology (POLMICRO). Aim: The aim is to assess the credibility of diagnostics conducted by microbiological laboratories in Poland, as well as the results and organization of the POLMICRO/ MIKOLOGIA (MYCOLOGY) and POLMICRO/SSE programs. Material and methods: The POLMICRO 2019 edition, according to the schedule, consisted of six rounds: five practical rounds and one theoretical round of an educational nature. The number of POLMICRO 2019 participants varied, depending on the round, from 430 to 438. In total, 443 laboratories took part in the program. The most (n = 438) laboratories took part in round I, and the least (n = 430) in round VI. Results: The shape and color of all test objects in the round devoted to microscopic preparations (4th round of POLMICRO 2019) were correctly assessed by 97.0% of laboratories (n = 419). Gram-negative rod strains belonging to the species Escherichia coli (PM-366, PM-367) and Klebsiella pneumoniae (PM-368, PM-369), from infection of the blood bed without a palpable site of infection, which were the subjects of the second round of POLMICRO 2019 studies, all participants correctly identified (100%; n = 433). While in the case of the MBL (metallo-β-lactamase) mechanism all participants (n = 439) correctly interpreted the presented picture, in the case of ESBL (β-lactamase with an extended substrate spectrum), seven laboratories (1.6%) misinterpreted the attached photos of phenotypic tests. Conclusions: In 2019, the Central Center for Quality Research in Microbiological Diagnostics, as previously planned, expanded its activity in the field of POLMICRO external laboratory control to include programs for mycological diagnostics (POLMICRO/ MIKOLOGIA) and diagnostics of etiological factors of gastrointestinal infections (POLMICRO/ SSE). Both the plan and the educational goals of the program have been achieved.

Variability of cycle threshold values in an external quality assessment scheme for detection of the SARS-CoV-2 virus genome by RT-PCR

ObjectivesThe qualitative results of SARS-CoV-2 specific real-time reverse transcription (RT) PCR are used for initial diagnosis and follow-up of Covid-19 patients and asymptomatic virus carriers. However, clinical decision-making and health management policies often are based additionally on cycle threshold (Ct) values (i.e., quantitative results) to guide patient care, segregation and discharge management of individuals testing positive. Therefore, an analysis of inter-protocol variability is needed to assess the comparability of the quantitative results.MethodsCt values reported in a SARS-CoV-2 virus genome detection external quality assessment challenge were analyzed. Three positive and two negative samples were distributed to participating test laboratories. Qualitative results (positive/negative) and quantitative results (Ct values) were assessed.ResultsA total of 66 laboratories participated, contributing results from 101 distinct test systems and reporting Ct values for a total of 92 different protocols. In all three positive samples, the means of the Ct values for the E-, N-, S-, RdRp-, and ORF1ab-genes varied by less than two cycles. However, 7.7% of reported results deviated by more than ±4.0 (maximum 18.0) cycles from the respective individual means. These larger deviations appear to be systematic errors.ConclusionsIn an attempt to use PCR diagnostics beyond the identification of infected individuals, laboratories are frequently requested to report Ct values along with a qualitative result. This study highlights the limitations of interpreting Ct values from the various SARS-CoV genome detection protocols and suggests that standardization is necessary in the reporting of Ct values with respect to the target gene.

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

BackgroundLaboratories 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.MethodsTwo 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.ResultsOf 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.ConclusionsUnexpected 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.