La Medicina di Laboratorio basata sull'evidenza: gli strumenti utili per una valutazione razionale degli esami di laboratorio

Claudia Canali, Tommaso Trenti
Dipartimento di Patologia Clinica, Nuovo Ospedale S. Agostino Estense, Modena

Biochimica Clinica: 2008; 32(4): 243-250 [Article in italian]

ABSTRACT
Evidence-based Laboratory Medicine-A guide for critical evaluation of laboratory tests. Evidence-based Laboratory Medicine (EBLM) is an essential part of the modern Laboratory Medicine practice. The EBLM process begins with the development of a clinically relevant question. Tools for assisting in question formulation include the Patient Intervention Comparator and Outcome (PICO) and Case Assay Predicate and Outcome (CAPO) strategies. Systematic reviews that have objectively collated evidence addressing the question are useful. The evidence collected must be critically evaluated using checklists developed for this purpose. Diagnostic performance of tests is frequently expressed in term of sensitivity, specificity, negative and positive predictive values, and diagnostic odds ratio. Tools such as receiver operator characteristic (ROC) curves and Fagan's diagram are important aids. Laboratorians must give thoughtful attention to convey information to clinicians in a useful format. Evidence-based guidelines and collaboration with clinicians are important for development of local care maps. Auditing the effectiveness of implemented care paths is an important part of quality management.

La determinazione dell'emoglobina A₂ nel sangue: attualità e prospettive
Olfat Shaker*, Ahmed Hashem, Lamia Mansour, Osama Taha
Centro Interdipartimentale per la Riferibilità Metrologica in Medicina di Laboratorio (CIRME) e Dipartimento di Scienze e Tecnologie Biomediche, Università degli Studi di Milano

Biochimica Clinica: 2008; 32(4): 251-259 [Article in italian]

ABSTRACT
The determination of hemoglobin A₂ in human blood: current perspectives. The increase of hemoglobin A2 (HbA2) in blood is the most important feature for the identification of b-thalassemia carriers. However, some carriers are difficult to identify because the results of HbA2 are not in the typical carrier range. The test has, therefore, to be performed with high accuracy. This review provides an update on the analytical and clinical aspects related to this measurement, as well summarizes the status of the international process of standardization of HbA2 measurement using a candidate reference measurement procedure based on quantitative peptide mapping.

Criteri per la selezione dei limiti di accettabilità dei risultati nei programmi di Valutazione Esterna della Qualità
Maurizio Borsotti, Massimo Quercioli, Carlo Franzini
Centro Regionale di Riferimento per il Controllo di Qualità, Azienda Ospedaliero-Universitaria Careggi, Firenze

Biochimica Clinica: 2008; 32(4): 260-268 [Article in italian]

ABSTRACT
Criteria for selecting limits for the acceptability of results in EQA schemes.Clinical biochemists are strongly concerned with the quality of the analytical results they produce: in principle, the overall quality is satisfactory if it allows advantageous application of the results to patients care. The analytical quality is monitored by appropriate assessment procedures, but it may appear cumbersome to assess the suitability of an observed quality level to the expected (medical) use of results. To this aim, quality goals (or quality specifications) need to be set. Biological variation-based quality specifications are frequently accepted for this purpose, but some drawbacks are observed in the generalized application of the concept. The alternative approach to the generation of reliable quality specifications is the “state-of-the-art”. We have considered as an acceptable estimate of the current state-of-the-art total error, the value corresponding to the 70th percentile of the distribution of the percent total errors obtained by the group of participants in an EQA scheme. The different concentrations of control materials assayed during one year operations of our EQA scheme made it possible to observe that the analytical state-of-the-art variability was correlated to concentrations for some components, while it was not for others. Accordingly, the biological variation-based quality specifications for total error, calculated at three quality level (minimum, desirable and optimum), were modulated following the state-of-the-art total error values observed at different concentrations. A new set of quality specifications for total error was thus selected and applied to the management of EQA schemes organized by our centre.

Valutazione di un metodo preparativo per la tipizzazione delle crioglobuline
Gabriella Passerini, Mladen Trbos, Andrea Motta, Massimo Locatelli, Fernanda Dorigatti
Diagnostica e Ricerca San Raffaele S.p.A., IRCCS San Raffaele, Milano

Biochimica Clinica: 2008; 32(4): 269-272 [Article in italian]

ABSTRACT
Evaluation of a preparative method for cryoglobulin characterizationWe evaluated a preparative method for cryoglobulin characterization (Cryokit, Alfa Wassermann) that allows samples to be managed without dedicated methods needing time and additional resources. The Cryokit consists of two solutions: solution A for washing cryoglobulins and solution B for dissolving them. The latter is a protein solution, which irreversibly disaggregate immunocomplexes allowing both quantitative and qualitative evaluation of cryoglobulins. During a first step of the work, 27 cryoprecipitates obtained with Cryokit were characterized by immunofixation electrophoresis (IFE) using the standard serum protein method on SAS3 (Alfa Wassermann). Results were compared with those obtained through the standard preparative treatment (saline washing and dissolving) and IFE with a dedicated method at 37° C on Hydrasis system (Sebia). The ability of the new method in reducing artifacts caused by physico-chemical cryoglobulin characteristics was specifically evaluated. After this step some modifications to the standard procedure were introduced. The stability of Cryokit precipitates was tested after 7 and 10 days of storage at 4 °C performing the IFE at room temperature. Afterwards, 36 additional samples (cryocrit range, <1%-29%) were analysed with Cryokit following the modified procedure (increased washing cycles and quantification of the total protein in the precipitate). Protein quantification and electrophoresis of the dissolved cryoglobulins were helpful to optimize sample dilution before IFE. The Cryokit allowed us to perform cryoglobulin IFE on routine electrophoresis analyzers with some advantages in the la-boratory organization. The procedure was reproducible and showed a clearer interpretation of immunoelectrophoretic patterns by reducing artifacts.

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