Confrontabilità dei risultati di due metodi per la determinazione della lattato deidrogenasi del siero dopo ricalibrazione al sistema di riferimento: impatto della commutabilità del calibratore

Giampaolo Cattozzo*, Elena Guerra, Ferruccio Ceriotti, Carlo Franzini per il Gruppo di Studio Enzimi SIBioC

*Azienda Ospedaliera Ospedale di Circolo e Fondazione Macchi, Varese

Biochimica Clinica: 2008; 32(5): 311-317 [Article in italian]

ABSTRACT
Comparability of results by two methods for measuring lactate dehydrogenase activity concentrations in serum after recalibration to the reference system: impact of commutability of calibration materials. Two main methodological principles are currently used in clinical laboratories to measure lactate dehydrogenase (LDH) activity concentrations in serum. They are based on measuring the LDH-catalyzed rate of transformation either of lactate into pyruvate (method LP) or of pyruvate into lactate (method PL). An IFCC reference procedure is also available, based on the former principle. When applied to patient sera, results from the LP method are about one half of those from the PL method. Scope of this work was to verify if recalibration with a commutable calibrator with value assigned by the reference method lead to comparability of the results from these two methods. The study included 109 serum samples and 26 candidate calibrator materials (22 stabilized materials and 4 serum pools); 5 additional serum pools surrogated patient sera in assessing the commutability of the candidate calibrators in the LP/IFCC, PL/IFCC and PL/LP pairs of methods. The frequencies of non-commutability of candidate calibrators were 0/26, 7/26 and 24/26 in the methods' pair LP/IFCC, PL/IFCC and PL/LP, respectively. Recalibration with a commutable material greatly improved the median PL-LP difference and median PL/LP ratio in the assay of 109 patient sera; with a non-commutable calibrator the improvement was less marked. In conclusion, commutable calibrators are useful in harmonizing LDH results from different methods. As the lack of commutability is an unpredictable event, it must be checked for every calibrator material.

Validazione di una metodica di screening per buprenorfina mediante confronto con metodo HPLC

Immacolata Amoroso, Daniela Giardiello, Rita Fiore, Agnese Morani, Patrizia Padulano, Vincenzo Vitulano, Luigi Vrenna

Polo Tossicologico di Riferimento Territoriale per le Farmacodipendenze e le Patologie Correlate "S.M. Loreto Crispi", A.S.L. Napoli 1

Biochimica Clinica: 2008; 32(5): 318-322 [Article in italian]

ABSTRACT
Validation of a screening method for buprenorphine in comparison with HPLC. The recent introduction of buprenorphine use by the drug addiction services has induced toxicology laboratories to develop new qualitative or semiquantitative urinary screening assays, which could be useful for both the patients and the physicians overseeing the treatment of drug dependence. The aim of this study was to verify whether the new Immunoanalysis EIA-Buprenorfina kit fits both the requirements of the physicians who follows drug-dependent subjects and those of the laboratory by validating it by comparison with HPLC. Results indicate that both method sensitivity and specificity are >90%.

La demonizzazione dei cosiddetti "test genetici"

Francesco Salvatore

Dipartimento di Biochimica e Biotecnologie Mediche, Università degli Studi di Napoli Federico II e CEINGE-Biotecnologie Avanzate, s.c. a. r.l., Napoli

Biochimica Clinica: 2008; 32(5): 323-325 [Article in italian]

ABSTRACT
The demonization of the so-called "genetic tests".The so-called "genetic tests" are often viewed as being different from other clinical laboratory tests, particularly because of their real or presumed predictivity regarding the development of a disease. Along the same line, just because of their very high predictivity, genetic tests have been "demonized" not only by the public, but even by people working in the area. This unwarranted attitude risks hampering research in this field. It is certainly true that genetic tests will become more popular, and even more effective, in revealing the possibility of contracting a disease. Consequently, they will contribute to the possibility of initiating preventive/prophylactic measures, and, moreover, individuals will be able to diminish their exposure to risk factors that can accelerate the onset or development of a given disease. Obviously, the genetic test should be performed in a laboratory with high expertise and where personnel can be trained at various levels, avoiding the spread to laboratories where competence is scarce and not yet well developed. This article lists some advantages of genetic testing and stresses the importance of the physician/patient relationship, particularly in view of genetic counselling and the implications of test results for the patient and for his family. Counselling is necessary before and after the test and must be multidisciplinary, including when necessary a psychologist. Another factor that contributes to the demonization of genetic tests is the assumption that they may adversely reflect on insurance policy premiums and also cause discrimination at work.

Il teorema di Bayes nella diagnostica di laboratorio

Marco Besozzi

Dipartimento di Medicina di Laboratorio, IRCCS Istituto Auxologico Italiano, Milano

Biochimica Clinica: 2008; 32(5): 326-329 [Article in italian]

ABSTRACT
Bayes' theorem in laboratory diagnostics.The work of the clinical laboratory consists in applying to a biological sample a measurement procedure to obtain data needed to produce a laboratory information useful to patients' care. In the probability theory, the Bayes' theorem relates conditional and marginal probabilities of two random events to compute posterior probabilities given the observations. If a patient is observed to suffer from a certain symptom, Bayes' theorem can be used to compute the probability that a proposed diagnosis is correct, given that observation. Single observations can furthermore be combined in sequence to obtain the probability of the clinical diagnosis. In this paper, an example concerning a nearly-perfect laboratory test for the detection of serum anti-HIV antibodies (test sensitivity 100%, test specificity 99.7%, with a disease prevalence of 0.3%) is proposed, from which two main conclusions can be drawn: 1) Bayes' theorem is a useful tool giving a quantitative measurement of the information added to the clinical diagnosis by a laboratory test; 2) Bayes' theorem is a useful tool giving a measurement of the cost/effectivenes ratio of screening and diagnostic strategies. For the clinical laboratory, understanding the bayesian basis of laboratory diagnostics and of the medical reasoning will be the challenge for the next future.

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