Traceability, reference systems and result comparability

M. Panteghini
Centro per la Riferibilità Metrologica in Medicina di Laboratorio (CIRME), Università di Milano

Biochimica Clinica: 2007; 31(4): 247-253 [Article in english]

ABSTRACT. The standardization of measurements is of high priority in Laboratory Medicine. At present, the international cooperation is involved in developing reference measurement systems (reference methods, reference materials, and reference laboratory networks) for measurands of clinical significance to reduce whenever possible uncertainty and to promote comparability of results for a better reliability of the information obtained from routine procedures. The implementation of the measurement traceability to the reference system actually provides one of the most important tools to support standardization in Laboratory Medicine aiming at result comparability regardless of the measurement procedure (test kit) and the clinical laboratory where analyses are carried out. The aim of this review is to discuss some concepts related to the achievement of standardization by the implementation of a metrologically correct measurement system, providing some examples to illustrate the complexity of this approach and the impact of these activities on patient care.

Gli intervalli di riferimento nel nuovo millennio

F. Cerotti
Coordinatore IFCC Committee on Reference Intervals and Decision Limits (C-RIDL), Diagnostica e Ricerca San Raffaele S.p.A., Milano

Biochimica Clinica: 2007; 31(4): 254-266 [Article in italian]

ABSTRACT. Reference intervals in the new millenium. The review presents an update on the reference intervals subject. The theoretical aspects are presented and the most critical issues are discussed. New facts are contributing to enhance the interest on this relatively old topic. Particularly, the requirements of ISO 15189, requesting that “biological reference intervals shall be periodically reviewed”, and the in vitro diagnostic (IVD) directive asking the manufactures to provide detailed information on reference intervals, drew renewed attention to it. The traditional approach to the definition of reference intervals, proposed by the IFCC documents remains valid. The use of data mining to obtain reference data from existing databases is discussed and essentially rejected as a mean to develop new reference intervals. New statistical approaches to discard outliers and to compute the reference limits are briefly introduced. The perspectives opened by the improvement in standardization through the implementation of the traceability concept are discussed and a model to define common reference intervals via multicenter experiments is presented and described in detail. The development of common reference intervals, obtained with traceable methods, that can be easily transferred and adopted by different clinical laboratories, can be an effective solution for the improvement of the present situation of proliferation of reference intervals not justified by differences in population characteristics or in analytical methodology.

Determinazione fotometrica della cistinuria

G. Cangiano*, A. Latte, M. Russo, F. Forte, E. Di Maina, M. D’Amora, M. Terribile, D Scognamiglio, R. Di Napoli, A. Risitano
*Laboratorio Patologia Clinica e 3U.O. Nefrologia, P.O. “Pellegrini”, ASL NA 1, Napoli

Biochimica Clinica: 2007; 31(4): 267-271 [Article in italian]

ABSTRACT. Photometric measurement of cystinuria. The monitoring of cystine excretion in the 24 h urine collection is of primary importance for the medical treatment of cystinuria.This paper describes the characteristics and the performance of a new photometric method for the urinary cystine determination. The method is fully automatized and replaces the old sodium nitroprusside Brand test. The reference interval, obtained on 230 healthy adults, was 21-148 mg/24h.

Valutazione di una nuova applicazione strumentale per la determinazione della ciclosporina con metodica CEDIA

G. Cangiano*, M. Russo, F. Forte, E. Di Maina, A. Latte, A. Sessa, M. D’Amora, A. Risitano
*Laboratorio Patologia Clinica e 2U.O. Nefrologia, Ospedale dei Pellegrini, ASL Napoli 1, Napoli

Biochimica Clinica: 2007; 31(4): 272-275 [Article in italian]

ABSTRACT. Evaluation of a new instrumental application for cyclosporine determination by CEDIA technology. The CEDIA method used for cyclosporine determination in our laboratory is based on two different system applications for low (25-450 mg/L) and high (450-2000 mg/L) range of analyte, respectively. In this paper, we suggest that on the Olympus AU400 analyzer the CEDIA assay should be modified to reach in a single application the analytical range of 75-1000 mg/L, really convenient for clinical purposes, enabling the determination of cyclosporine concentrations both before administration (basal value) and two hours later (peak value) in a single run.

Variabilità delle frazioni emoglobiniche dalla nascita all’età adulta in condizioni fisiologiche e patologiche

G. Ivaldi, D. Leone, C. Viaggi, D. Pascotto
Laboratorio di Genetica, Settore Microcitemia, Ospedali Galliera, Genova

Biochimica Clinica: 2007; 31(4): 276-279 [Article in italian]

ABSTRACT. Variability of the hemoglobin fractions from birth to the adult age under physiological and pathological conditions. Many investigations have been carried out in the past with the aim of determining the fractional concentrations of hemoglobin (Hb) A and Hb F in neonates. Neonatal identification and quantification of various hemoglobins may be required to confirm or to exclude formulated diagnosis during the fetal development, to predict serious disorders of globin chain synthesis, to identify an abnormality in a presymptomatic phase, to explain a hematological abnormality or to know the hemoglobin composition in relationship to the presence of remarkable clinical symptoms. We have determined at birth and in several ages during the switching from fetal to adult hemoglobin synthesis the percentages of Hb F, Hb A and Hb A2 in physiological conditions and in individuals with beta-thalassemia trait or Hb S, Hb C, Hb E or alpha Hb variants. More than 7000 subjects were examined by HPLC and in selected cases the hemoglobin fractions were also quantificated by elution after cellulose acetate electrophoresis. Diagnoses were confirmed with biochemical or molecular methods as suggested by hemoglobinopathy guidelines.

Valutazione della specificita’ di un metodo HPLC nella determinazione della transferrina carboidrato-carente

V. Bianchi, A. Roveta, C. Arfini
Laboratorio di Tossicologia, Dipartimento di Patologia Clinica, Azienda Ospedaliera SS Antonio e Biagio e C. Arrigo, Alessandria

Biochimica Clinica: 2007; 31(4): 280-285 [Article in italian]

ABSTRACT. Evaluation of the specificity of a HPLC method for determination of the carbohydrate-deficient transferrin. Carbohydrate-deficient transferrin (CDT), and more specifically its disialo isoform, is considered the most reliable marker for detection of chronic alcohol abuse and it is widely used both in clinical monitoring of the alcoholic patient treatment and in forensic toxicology, mainly when legal aspects of driving license reapplication are considered. In clinical laboratories, CDT is quantified by different techniques, some of which are known to be subjected to inaccuracy due to either inefficient isoform separation or high concentrations of interfering serum proteins. The aim of this work is to evaluate a commercial HPLC method by verifying the efficiency in the disialo isoform separation even in presence of high amount of trisialotransferrin and to investigate HPLC specificity in serum samples containing potentially interfering proteins by comparison to the transferrin immunosubtraction technique.

Toward standardization of carbohydrate-deficient transferrin (CDT) measurements: I. Analyte definition and proposal of a candidate reference method

Jan-Olof Jeppsson*, T. Arndt, F. Schellenberg, J. P.M. Wielders, R. F. Anton, J. B. Whitfield,
A. Helander

*Malmö University Hospital, Malmö, Sweden

Biochimica Clinica: 2007; 31(4): 286-289 [Article in english]

ABSTRACT. An alcohol-associated change in the serum transferrin glycoform pattern, carbohydrate-deficient transferrin (CDT), is used as a biomarker for chronic moderate to heavy alcohol consumption. A current limitation in CDT analysis is the lack of standardization, which hampers clinical and analytical comparison between studies. This situation prompted initiation of a Working Group (WG) on CDT standardization under the auspices of the IFCC. The standardization work aims to define and validate the analyte, select a reference method, work out procedures for the production of reference materials, and make suggestions for the clinical usage of CDT. The first recommendation of the WG is that disialotransferrin should be the primary target molecule for CDT measurement and the single analyte on which the CDT standardization is based. It is further recommended that HPLC should be the analytical principle considered as the basis of an interim reference method until a suitable mass spectrometric reference method is established. In clinical use, CDT should be expressed in a relative amount (% CDT) to compensate for variations in the total transferrin concentration.

Indagine conoscitiva sulla determinazione quantitativa della albumina nelle urine nei laboratori italiani

M.S. Graziani, C. Lo Cascio, A.L. Caldini, F. Ghiara, B. Salvadori, S. Secchiero, R. Testa,
A. Mosca per il Gruppo di Studio Intersocietario Diabete Mellito
Laboratorio di Analisi Chimico Cliniche ed Ematologiche, Ospedale Civile Maggiore, Azienda Ospedaliera di Verona

Biochimica Clinica: 2007; 31(4): 290-296 [Article in italian]

ABSTRACT. National survey on quantitative measurement of albumin in urine. The quantitative measurement of urinary albumin is a key-point in the management of diabetic patients. However, standardization of this assay is still lacking. In order to investigate this aspect, a survey has been performed among Italian laboratories. A questionnaire with 21 questions has been distributed to the members of two Italian Societies (SIBioC and SIMeL) and to the participants to an EQAS. Questions concerned the main preanalytical, analytical and postanalytical aspects. We collected 153 questionnaires. The mostly used specimen to measure albumin in urine was the 24 h sample (56%), followed by the spot sample (18%), and the timely-collected sample (8%). The turbidimetric methods were used by the majority of laboratories (55%) followed by the nephelometric ones (39%). IQC procedures are adopted by 85% of laboratories, while EQAS are perfomed only by a minority (28%). A great variety of units were used. 37% of the participants reported 24 h excretion mass, 32% concentration in terms of mass per volume of urine, 22% ratio to urinary creatinine and 11% excretion mass per min. Different units such as mg, mg, dL, L, mol were reported within the same category of report. Only for 36% of the participants the decision limits for urinary albumin were found in agreement with the recommendations of the American Diabetes Association. From the data we have collected it is evident that only a minority of laboratories follow the current recommendations on the measurement of urinary albumin. An information and education campaign is strongly needed.

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