Ilenia Infusino

Soluble Transferrin Receptor (sTfR) and sTfR/log Ferritin Index for the Diagnosis of Iron-Deficiency Anemia A Meta-Analysis

Determination of serum soluble transferrin receptor (sTfR) is proposed to distinguish between iron-deficiency anemia and anemia of chronic disease. Here we conducted a meta-analysis of the literature to evaluate the diagnostic efficacy of sTfR and sTfR/log ferritin index. The meta-analysis included 18 sTfR and 10 sTfR index studies. Three sTfR index studies were, however, eliminated as outliers. The odds ratio was significant for both sTfR (22.9, 95% confidence interval [CI], 9.6-55.0) and sTfR index (9.5, 95% CI, 5.0-18.1) in a heterogeneous set of studies. Meta-analysis for sensitivity, specificity, and likelihood ratios (LRs) was performed only in a subset of 10 sTfR studies. The overall sensitivity, specificity, and positive and negative LRs were 86%, 75%, 3.85, and 0.19, respectively, with an area under summary receiver operating characteristic curve of 0.912 (standard error, 0.039). Additional studies are needed to define the overall diagnostic accuracy of sTfR.

Standardization in clinical enzymology: a challenge for the theory of metrological traceability.

Abstract The goal of standardization for measurement of the catalytic concentration of enzymes is to achieve comparable results in human samples, independent of the reagent kits, instruments, and laboratory where the assay is performed. To pursue this objective, the IFCC has established reference systems for the most important clinical enzymes. These systems are based on the following requirements: a) reference methods, well described and evaluated extensively; b) suitable reference materials; and c) reference laboratories operating in a highly controlled manner. When these reference systems are used appropriately, the diagnostic industry can assign traceable values to commercial calibrators. Clinical laboratories that use procedures with validated calibrators to measure human specimens can now obtain values that are traceable to higher-order reference procedures. These reference systems constitute the structure of the traceability chain to which the routine methods can be linked via an appropriate calibration process, provided that they have a comparable specificity (i.e., they are measuring the same catalytic quantity). Clin Chem Lab Med 2010;48:301–7.

Performance criteria for combined uncertainty budget in the implementation of metrological traceability

Abstract The measurement uncertainty budget should combine the uncertainty of higher order references, the uncertainty of commercial system calibration, the system imprecision and individual laboratory performance in terms of variability. Here we recommend that no more than one third of the total uncertainty budget, established by appropriate analytical performance specifications, is consumed by the uncertainty of references and approximately 50% of the total budget consumed by the manufacturer’s calibration and value transfer protocol. The remaining 50% should be available for the commercial system imprecision (including the batch to batch variation of the reagents) and individual laboratory performance in order to fulfil the uncertainty goal. For commercial systems to work properly, in vitro diagnostics (IVD) manufacturers will need to take more responsibility and ensure the traceability of the combination of platform, reagents, calibrators and control materials for system alignment verification that only as such (as a whole) are certified (“CE marked”) by the manufacturer itself in terms of traceability to the selected reference measurement system. Particularly, IVD manufacturers should report the combined (expanded) uncertainty associated with their calibrators when used in conjunction with other components of their analytical system (platform and reagents). This is more than what they are currently providing as traceability and uncertainty information.

Serum albumin: accuracy and clinical use.

Albumin is the major plasma protein and its determination is used for the prognostic assessment of several diseases. Clinical guidelines call for monitoring of serum albumin with specific target cut-offs that are independent of the assay used. This requires accurate and equivalent results among different commercially available methods (i.e., result standardization) through a consistent definition and application of a reference measurement system. This should be associated with the definition of measurement uncertainty goals based on medical relevance of serum albumin to make results reliable for patient management. In this paper, we show that, in the current situation, if one applies analytical goals for serum albumin measurement derived from its biologic variation, the uncertainty budget derived from each step of the albumin traceability chain is probably too high to fulfil established quality levels for albumin measurement and to guarantee the accuracy needed for clinical usefulness of the test. The situation is further worsened if non-specific colorimetric methods are used for albumin measurement as they represent an additional random source of uncertainty.

How to assess the quality of your analytical method

Abstract Laboratory medicine is amongst the fastest growing fields in medicine, crucial in diagnosis, support of prevention and in the monitoring of disease for individual patients and for the evaluation of treatment for populations of patients. Therefore, high quality and safety in laboratory testing has a prominent role in high-quality healthcare. Applied knowledge and competencies of professionals in laboratory medicine increases the clinical value of laboratory results by decreasing laboratory errors, increasing appropriate utilization of tests, and increasing cost effectiveness. This collective paper provides insights into how to validate the laboratory assays and assess the quality of methods. It is a synopsis of the lectures at the 15th European Federation of Clinical Chemistry and Laboratory Medicine (EFLM) Continuing Postgraduate Course in Clinical Chemistry and Laboratory Medicine entitled “How to assess the quality of your method?” (Zagreb, Croatia, 24–25 October 2015). The leading topics to be discussed include who, what and when to do in validation/verification of methods, verification of imprecision and bias, verification of reference intervals, verification of qualitative test procedures, verification of blood collection systems, comparability of results among methods and analytical systems, limit of detection, limit of quantification and limit of decision, how to assess the measurement uncertainty, the optimal use of Internal Quality Control and External Quality Assessment data, Six Sigma metrics, performance specifications, as well as biological variation. This article, which continues the annual tradition of collective papers from the EFLM continuing postgraduate courses in clinical chemistry and laboratory medicine, aims to provide further contributions by discussing the quality of laboratory methods and measurements and, at the same time, to offer continuing professional development to the attendees.

Soluble transferrin receptor in complicated anemia.

Determination of serum soluble transferrin receptor (sTfR) has been proposed to identify iron-deficiency anemia (IDA) in patients affected by concurrent inflammatory disease that may spuriously increase ferritin concentration. The aim of this study was to critically review the available literature to assess the diagnostic efficacy of sTfR in complicated anemia. The criteria for study selection were: enrolment of patients with complicated anemia; bone marrow examination used as diagnostic gold standard for IDA; evaluation of sTfR vs. ferritin and binary data presentation. Six published studies met the criteria. However, the small size and wide heterogeneity of the studies did not allow us to conduct a meta-analysis. sTfR was overall more sensitive, even though it was evident that the ferritin sensitivity was influenced by selected cut-offs. Well-designed studies are still needed to define the added value, if any, of sTfR to ferritin for IDA detection in complicated anemia.

Role and Responsibilities of Laboratory Medicine Specialists in the Verification of Metrological Traceability of in Vitro Medical Diagnostics / Uloga I Odgovornosti Specijalista Laboratorijske Medicine U Verifikaciji Metrološke Sledljivosti In Vitro Medicinske Dijagnostike

Summary To be accurate and equivalent, laboratory results should be traceable to higher-order references. Furthermore, their quality should fulfill acceptable measurement uncertainty as defined to fit the intended clinical use. With this aim, in vitro diagnostics (IVD) manufacturers should define a calibration hierarchy to assign traceable values to their system calibrators and to fulfill during this process uncertainty limits for calibrators, which should represent a proportion of the uncertainty budget allowed for clinical laboratory results. It is therefore important that, on one hand, the laboratory profession clearly defines the clinically acceptable uncertainty for relevant tests and, on the other hand, endusers may know and verify how manufacturers have implemented the traceability of their calibrators and estimated the corresponding uncertainty. Important tools for IVD traceability surveillance are quality control programmes through the daily verification by clinical laboratories that control materials of analytical systems are in the manufacturer’s declared validation range [Internal Quality Control (IQC) component I] and the organization of Exter nal Quality Assessment Schemes meeting metrological criteria. In a separate way, clinical laboratories should also monitor the reliability of employed commercial systems through the IQC component II, devoted to estimation of the measurement uncertainty due to random effects, which includes analytical system imprecision together with individual laboratory performance in terms of variability. Krotak sadrzaj Da bi bili tacni i ekvivalentni, laboratorijski rezultati treba da budu sledljivi do referenci viseg reda. Stavise, njihov kvalitet treba da ispostuje prihvatljivu mernu nesigurnost definisanu tako da odgovara planiranoj klinickoj upotrebi. Sa ovim ciIjem, proizvodaci in vitro dijagnostickih sredstava treba da definisu hijerarhiju kalibracije kako bi dodelili sledljive vrednosti kalibratorima svojih sistema i kako bi u toku ovog procesa ispostovali granice nesigurnosti za kalibratore, sto bi trebalo da predstavlja srazmeran deo budzeta za nesigurnost odobrenog za rezultate klinicke laboratorije. Stoga je vazno da, s jedne strane, laboratorijski strucnjaci jasno definisu klinicki prihvatljivu nesigurnost za relevantne testove, a da, s druge strane, krajnji korisnici mogu da znaju i verifikuju na koji su nacin proizvodaci implementirali sledljivost svojih kali- bratora i procenili odgovarajucu nesigurnost. Vazne alatk|e za nadzor sledljivosti in vitro dijagnostickih sredstava su progra- mi za kontrolu kvaliteta putem dnevne verifikacije od strane klinickih laboratorija da su kontrolni materijali analitickih sistema u okviru validacionog opsega koji je deklarisao proizvodac (I komponenta programa Internal Quality Control, IQC) i organizacija sema za eksternu procenu kvaliteta (External Quality Assessment Schemes) koje ispunjavaju metroloske kriterijume. Klinicke laboratorije takode treba zasebno da prate pouzdanost primenjenih komercijalnih sistema kroz II komponentu programa IQC, posvecenu proceni merne nesigurnosti usled nasumicnih efekata, koja obuhva- ta nepreciznost analitickih sistema kao i performanse pojedinacnih laboratorija u pogledu varijabilnosti

Plasma or serum samples: measurements of cardiac troponin T and of other analytes compared

Abstract Conflicting data in the literature concern possible differences in the immunochemical measurement of cardiac troponins, either in plasma or in serum. In order to address this specific point, 96 serum and heparin-plasma pairs were obtained for cardiac marker measurement [cardiac troponin T (cTnT); myoglobin (Myo) and creatine kinase-MB isoenzyme (CK-MB)]; 29 additional “common” analytes were measured in 77 such samples. The cardiac markers were measured by electrochemiluminescence (Elecsys 2010, Roche); the other analytes by established automated methods (Modular, Roche). Mean plasma/serum ratios for cTnT (0.95), creatine kinase-MB (1.01) and myoglobin (0.99) were comparable with those of the 29 common analytes (interval of means 0.83–1.05). The distribution of the plasma-serum differences also showed similarities between cardiac markers and other analytes. A few outlier plasma-serum differences (3–5%) were measured for both categories of analytes. Addition of heparin to serum (51 samples) caused decreased cTnT (mean ratio 0.92). In 3 of 51 such samples the cTnT decrease was more marked, but in a second sample from the same subjects (1 week later) such a prominent, heparin-induced loss of cTnT no longer appeared. In conclusion, plasma-serum differences in immuno-reactive cTnT compare with those observed for other analytes. In occasional heparin-plasma samples immunochemical measurement of cTnT may give exceptionally low values. However, in our sample group of 96 patients (cTnT lower or higher than the cut-off in, respectively, 24 and 72 patients), no misclassification occurred if plasma instead of serum cTnT values were considered.

Precision and long-term stability of capillary electrophoresis measurement of serum protein zones.

BACKGROUND Analytical evaluations of an available system for capillary zone electrophoresis (CZE) of serum protein have been reported. However, data concerning long-term precision and stability of the system, operated under routine conditions, are lacking. We report data from an internal quality control (QC) scheme, obtained over a 1-year period. METHODS Measurements were done with a pair of instruments (Beckman Paragon CZE 2000 system), each equipped with seven capillaries. After preliminary (1 month) assessment of possible inter-capillary and inter-instrument variations, the QC material (a home prepared serum pool stored in the frozen state) was assayed daily over a 1-year period. RESULTS Maximum inter-capillary and inter-instrument differences were 3.1% and 2.4%. No significant trend was observed for daily values (205 measurements over 1 year); in the same period overall imprecision values (CV) were in the interval 1.2% (albumin) to 3.2-6.1% (globulin zones). Mean monthly imprecision (CV) values were in the interval 1.1% (albumin) to 5.2% (globulin zones). There was no significant trend of monthly means with time. The observed imprecision values were within the biological variation-derived goals for imprecision. CONCLUSIONS It is concluded that the assessed analytical instruments, operated in routine conditions, show long-term stability and imprecision consistent with the clinical use of the results produced.

Progress and impact of enzyme measurement standardization.

Abstract International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) has established reference measurement procedures (RMPs) for the most popular enzymes. Manufacturers should assign values to commercial calibrators traceable to these RMPs to achieve equivalent results in clinical samples, independent of reagent kits, instruments, and laboratory where the measurement is carried out. The situation is, however, far from acceptable. Some manufacturers continue to market assays giving results that are not traceable to internationally accepted RMPs. Meanwhile, end-users often do not abandon assays with demonstrated insufficient quality. Of the enzyme measurements, creatine kinase (CK) is satisfactorily standardized and a substantial improvement in performance of marketed γ-glutamyltranspeptidase (GGT) assays has been demonstrated. Conversely, aminotransferase measurements often exceed the desirable analytical performance because of the lack of pyridoxal-5-phosphate addition in the commercial reagents. Measurements of lactate dehydrogenase (LDH), alkaline phosphatase (ALP), and α-amylase (AMY) still show major disagreement, suggesting the need for improvement in implementing traceability to higher-order references. This is mainly the result of using assays with different analytical selectivities for these enzymes. The definition by laboratory professionals of the clinically acceptable measurement uncertainty for each enzyme together with the adoption by EQAS of commutable materials and use of an evaluation approach based on trueness represent the way forward for reaching standardization in clinical enzymology.