A B S T R A C T S   N U M E R O   3 / 1998

Measurement of bile acids in serum: comparison of an automatic with a manual method.

*Galli L, Cappellini A, Berni R, Giordani R
*Laboratorio di Analisi Cliniche - Clinica medica II - Università degli Studi di Pisa - Via Roma, 55 - 56100 Pisa

Biochimica Clinica 1998; 22(3): 113-115 [Article in italian]

ABSTRACT. The measurement of bile acids in serum is a sensitive and specific test for liver function. We compared a manual and a mechanized (Hithachi 911 analyzer) method for such a measurement. Both methods were based on the same principle, including action of 3-a-hydroxysteroid dehydrogenase with NADH formation, followed by photometric measurement by coupled NBT-based indicator reaction. Duplicate measurements on 46 normal and pathological serum samples showed good correlation, and equal classification power of the two methods, the automated method's results showing about - 8% proportional systematic error in comparison with the manual measurement procedure.

Plasma instead of serum: a comparison of results for 25 analytes measured on the Ektachem E550.

*Frezzotti A, Margarucci Gambini AM, Coppa G, De Sio G
*Laboratorio di Analisi Chimico Cliniche e Microbiologiche, Ospedale Regionale, 60100 Ancona

Biochimica Clinica 1998; 22(3): 116-121 [Article in english]

ABSTRACT. The aim of our study was to evaluate heparinized plasma as an alternative to serum sample for the determination of the most common analytes and to investigate the potential interfering effect of heparin on Ektachem tests. We compared the results from the measurement of 25 analytes in plasma/serum pairs from 110 blood samples, with the Ektachem E500 analyzer. We also measured the 25 analytes in 10 pooled sera supplemented with heparin to up three times the usual concentration (32 U.S.P. units/mL). The plasma-serum differences were statistically significant (Student's paired t-test, p < 0.01) but clinically negligible (i.e.lower than the critical difference) for alanine amino transferase, albumin, aspartate aminotransferase* ("new" visible method), total bilirubin, cholinesterase, glucose, lactate dehydrogenase, potassium, and uric acid. Statistically and clinically significant differences were observed for amylase and total protein (critical difference at p=0.95), for lipase (critical difference at p=0.90), and for aspartate aminotransferase** ("old" UV method at) (critical difference at p=0.80). Heparin interfered with the amylase and aspartate amino transferase** tests at the usual concentration: in the case of aspartate aminotransferase** such interference depended on the heparin concentration. In conclusion, with the tested analytical system, plasma and serum can be used interchangeably for most tests; only for amylase, aspartate aminotransferase**, lipase and total protein a correction for the analytical bias may be needed; for the aspartate aminotransferase** test the tubes incompletely filled, with a higher than usual heparin concentration, may require a specific correction.

Glycated haemoglobin (Hb A1c): reference values in HbS heterozygosis?

*Sall ND, Toure M, Sarr NG, Sall PL, Seck I
*Laboratoire de Biochimie Médicale, Faculté de Médecine de Dakar UCAD-SENEGAL

Biochimica Clinica 1998; 22(3): 122-123 [Article in french]

ABSTRACT. The blood content of HbA1c has been measured by ion exchange chromatography in a control group of 36 non-diabetic normal subjects, and in 18 non-diabetic subjets heterozygous for HbS. In all cases the blood haemoglobin pattern was confirmed by haemoglobin electrophoresis at alkaline and acid pH. In accordance with previous observations, the HbA1c content measured in the HbS carriers (3,33 æ 0,47%) was significantly higher than that observed in the control group (5,83 æ 0.54%). These results are discussed in relation to the correct interpretation of the HbA1c values measured in haemoglobinopathic subjects.

Antiphospholipid antibodies in elderly with ischemic stroke

*Berni I, Conforti G, Costantini A, Marinello E, Pagani R
*Laboratorio analisi e reparto di riabilitazione motoria - Casa di Cura "Villa Immacolata" - San Martino Al Cimino (VT)

Biochimica Clinica 1998; 22(3): 124-127 [Article in italian]

ABSTRACT. In order to evaluate the prevalence of antiphospholipid antibodies in elderly patients with a diagnosis of estabilished ischaemic stroke, we selected 100 subjects (aged 64-88 years) with cerebral ischaemia who underwent a comprehensive clinical and instrumental assessment for the cerebrovascular event, and 175 age-matched subjects, representing the control group. In all cases we tested for the presence of lupus anticoagulants and anticardiolipin antibodies. We found that the presence of antiphospholipid antibodies in stroke patients is higher (33%) than controls (21.7%), but the difference is not statistically significant (chi square test p > 0.5). More over while no significant difference we found in anticardiolipin antibodies (14% in stroke patients, 20% in controls), lupus anticoagulants were positive 23 out of 100 patients, but only in 6 our of 175 controls. This difference was statistically significant (chi square test p=0,01). These findings suggest that in elderly subjects with cerebral ischaemia, only lupus anticoagulants are statistically significant.

Neural network and laboratory medicine.

*Ognibene A, Messeri G
*Laboratorio di Endocrinologia e Farmaco-Tossicologia, Azienda Ospedaliera Careggi, Firenze

Biochimica Clinica 1998; 22(3): 128-132 [Article in italian]

ABSTRACT. Artificial neural network (NN) are computer programs which can be used to discover complex relations within data sets. Structurally, they are very similar to a biological neural network, such as the human brain. They consist of a set of processing units (nodes) which simulate neurons and are interconnected via a set of synapses. They behave similarly to human brain: they first undergo a training phase and later on solve a problem thank to the acquired experience. NN are presently used in several fields such as simultaneous translation, marketing forecast, protein structure etc. The main features, pattern recognition and sample classification, make them particularly attractive in the bio-medical field. Finally, in laboratory medicine, NN are expected to provide substantial contributes as a support to medical decisions.

Evaluation of an immunoseparation method for the direct measurement of plasm low density lipoprotein cholesterol.

*Trombini W, Bonora R, Pagani F, Panteghini M
*1° Laboratorio Analisi Chimico-Cliniche, Spedali Civili, 25125 Brescia

Biochimica Clinica 1998; 22(3): 133-139 [Article in italian]

ABSTRACT. We evaluated the performance of a direct, immunoseparation-based method for determination of cholesterol contained in serum low-density lipoproteins (LDL-C). The reagent utilizes polyclonal antibodies to human apolipoproteins A-I and E that selectively remove the other lipoproteins from sample, while LDL remains in the filtrate to be measured. Specificity studies showed that approximately â10% of HDL cholesterol in plasma remained in the filtrate with LDL-C. Furthermore, a negative interference on the method was demonstrated with plasma triglycerides > 700 mg/dL. Plasma lipoprotein(a) was collected entirely in the filtrate and computed as LDL-C. Total assay imprecision (CV) was between 2.6% and 4.3%. Considering the different analytic approach of the methods evaluated (direct method vs Friedewald formula or quantitative electrophoresis), the comparison studies showed good correlations with r > 0.9. However, the comparison between direct method and electrophoresis resulted in a significant proportional bias, that was reduced when in LDL-C electrophoresis results was computed also lipoprotein(a) cholesterol, determined separately in this method. To conclude, the major advantage of the direct immunoseparation method is the possibility to determine accurately LDL-C in sera with a hypertriglyceridemia of intermediate grade, thus overcoming the well-known pitfall of the Friedewald equation.

Evaluation of the analytical characteristics and assessment of the praticability of the LIASION system.

*Stefani A, Brigato L, Masiero M, Plebani M
*Centro di Ricerca Biomedica della Regione Veneto (Castelfranco Veneto)

Biochimica Clinica 1998; 22(3): 140-144 [Article in italian]

ABSTRACT. Aim of this work was to evaluate the analytical performance and the praticability of a new diagnostic system for immunoassays, the LIAISON. In particular we assessed the performance of the system in the assay of two tumor markers, CEA and CA125. The linearity, carry-over and agreement of the methods evaluated in comparison to those commonly used in our laboratory were found to be satisfactory. The intra-assay analytical imprecision of CA 125 ranged from 4.5 to 4.8%; the inter-assays coefficient of variation ranged from 5.5 to 6.6%. The intra-assay coefficient of variation for CEA ranged from 4.2 to 5.7% and the inter-assay between 3.4 and 5.4%. These coefficients of variation might be improved in order to reduce the total variability of this marker, making more effective the utilization of the CEA in the clinical follow-up of patients. Finally, the praticability of the LIAISON was found to be excellent.

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