External quality assessment schemes for glucose measurements in Germany: factors for successful participation, analytical performance and medical impact.

BACKGROUND: Determination of blood glucose concentration is one of the most important measurements in clinical chemistry worldwide. Analyzers in central laboratories (CL) and point-of-care tests (POCT) are both frequently used. In Germany, regular participation in external quality assessment (EQA) schemes is mandatory for laboratories performing glucose testing. METHODS: Glucose testing data from the two German EQAs "Reference Institute for Bioanalytics" (RfB) and "INSTAND - Gesellschaft zur Förderung der Qualitätssicherung in medizinischen Laboratorien" (Instand) were analyzed from 2012 to 2016. Multivariable odds ratios (OR) for the probability to reach a "good" result were calculated. Imprecision and bias were determined and clinical risk of measurement errors estimated. RESULTS: The device employed was the most important variable required for a "good" performance in all EQAs. Additional participation in an EQA for CL automated analyzers improved performance in POCT EQAs. The reciprocal effect was less pronounced. New participants performed worse than experienced participants especially in CL EQAs. Imprecision was generally smaller for CL, but some POCT devices reached a comparable performance. Large lot-to-lot differences occurred in over 10% of analyzed cases. We propose the "bias budget" as a new metric to express the maximum allowable bias that still carries acceptable medical risk. Bias budgets were smallest and clinical risks of errors greatest in the low range of measurement 60-115 mg/dL (3.3-6.4 mmol/L) for most devices. CONCLUSIONS: EQAs help to maintain high analytical performances. They generate important data that serve as the foundation for learning and improvement in the laboratory healthcare system.

Results of the first external quality assessment scheme (EQA) for isolation and analysis of circulating tumour DNA (ctDNA).

BACKGROUND: Circulating tumour DNA (ctDNA) is considered to have a high potential for future management of malignancies. This pilot external quality assessment (EQA) scheme aimed to address issues of analytical quality in this new area of laboratory diagnostics. METHODS: The EQA scheme consisted of three 2-mL EDTA-plasma samples spiked with fragmented genomic DNA with a mutant allele frequency ranging from 0% to 10% dedicated to the analysis of nine known sequence variations in KRAS codon 12/13 and of BRAF V600E. Laboratories reported: (1) time elapsed for processing, (2) storage temperatures, (3) methods for extraction and quantification, (4) genotyping methodologies and (5) results. RESULTS: Specimens were sent to 42 laboratories from 10 European countries; 72.3% reported to isolate cell-free DNA (cfDNA) manually, 62.5% used the entire plasma volume for cfDNA isolation and 38.5% used >10% of cfDNA extracted for downstream genotyping. Of the methods used for quantification, PicoGreen demonstrated the lowest coefficient of variation (33.7%). For genotyping, 11 different methods were reported with the highest error rate observed for Sanger sequencing and the lowest for highly sensitive approaches like digital PCR. In total, 197 genotypes were determined with an overall error rate of 6.09%. CONCLUSIONS: This pilot EQA scheme illustrates the current variability in multiple phases of cfDNA processing and analysis of ctDNA resulting in an overall error rate of 6.09%. The areas with the greatest variance and clinical impact included specimen volume, cfDNA quantification method, and preference of genotyping platform. Regarding quality assurance, there is an urgent need for harmonisation of procedures and workflows.

EGFR immunohistochemistry as biomarker for antibody-based therapy of squamous NSCLC - Experience from the first ring trial of the German Quality Assurance Initiative for Pathology (QuIP®).

BACKGROUND: EGFR and its downstream signaling pathway are important targets for cancer therapy. Recently, the monoclonal anti-EGFR antibody Necitumumab in combination with gemcitabine and cisplatin was approved (EMA/14106/2016) for first-line treatment of squamous non-small cell carcinoma (SqNSCLC). Eligibility was restricted to cases with positive EGFR expression. In this context, a ring trial of the Quality Assurance Initiative for Pathology (QuIP®) was launched to prepare the German pathology community for a reliable and reproducible, immunohistochemically based biomarker test. MATERIALS AND METHODS: The trial was set up by a three-step approach. Two lead institutes were nominated to organize the trial process and to select appropriate cancer samples. These were first tested by the H-score (range 0-300) to identify positive and negative cases. Seven additional pathology institutes with experience in EGFR immunohistochemistry each tested the selected panel of identical cases (internal ring trial) to confirm the suitability of samples and scoring criteria. Then the open ring trial for all institutes of pathology in German speaking countries was announced. RESULTS: For the internal trial 8 EGFR-positive and 2 negative lung sqNSCLC samples were selected. A cut-off value of cell membranous staining in≥1% of tumor cells was introduced to define a case as EGFR negative or positive. Two points were attainable per correctly assessed sample leading to a maximum of 20 points,≥18 points were required for a successful participation. All 7 panel institute passed this barrier, 5 with the maximum of 20 points and two with one error (18 points) being related to one case with incorrect interpretation of cytoplasmic versus membranous staining and one case with an H-score of 2 as being considered EGFR positive. A second cut-off value (H-score≥3) was therefore introduced. In the open ring trial, 34 institutions participated of which 28 were successful according to the above criteria. The trial revealed a high reproducibility despite the use of different EGFR antibodies and detection systems. There was no association between technical parameters and trial failure. Again, one participant misinterpreted the subcellular EGFR localization. CONCLUSIONS: The first nationwide ring test for determination of EGFR IHC expression in sqNSCLC could be successfully performed in a very tight time frame. By this, the national pathology community was prepared to incorporate this marker in the panel of predictive cancer tests in a quality assessed manner and to initiate and accompany future studies on EGFR pathway pathology.

Thirteen Years of an International External Quality Assessment Scheme for Genotyping: Results and Recommendations.

BACKGROUND: Suboptimal laboratory procedures resulting in genotyping errors, misdiagnosis, or incorrect reporting bear greatly on a patient's health management, therapeutic decisions made on their behalf, and ultimate outcome. Participation in external quality assessment (EQA) is a key element of quality assurance in molecular genetic diagnostics. Therefore, the Reference Institute for Bioanalytics has tried for 13 years to improve the quality of genetic testing by offering an EQA for different clinically relevant sequence variations. METHODS: Within each of the biannual EQA schemes offered, up to 18 samples of lyophilized human genomic DNA were provided for up to 50 different molecular genetic tests. Laboratories were asked to use their routine procedures for genotyping. At least 2 expert peer assessors reviewed the final returns. Data from 2002 to 2014 were evaluated. RESULTS: In total, 82 462 reported results from 812 characterized samples were evaluated. Globally, the number of participants increased each year along with the number of sequence variations offered. The error rate decreased significantly over the years with an overall error rate of 1.44%. Additionally, a decreased error rate for samples repeated over time was noted. Interestingly, the error rate showed a high difference depending on the locus analyzed and the method used. CONCLUSIONS: Based on the evaluation of this long-term EQA scheme, various recommendations can be given to improve the quality of molecular genetic testing, such as the use of 2 different methods for genotyping. Furthermore, some methods are inappropriate for analysis of certain sequence variations.