AVariabilità biologica dell’emoglobina glicata: un’analisi sistematica della letteratura

F. Braga*, A. Dolci, A. Mosca, M. Panteghini

*Centro Interdipartimentale per la Riferibilità Metrologica in Medicina di Laboratorio (CIRME), Università degli Studi, Milano
Biochimica Clinica: 2009;33(5):297-302 [Article in italian]

ABSTRACT
Biological variability of glycated hemoglobin: a systematic review of the literature. Glycated hemoglobin (HbA1c) is the product of the nonenzymatic reaction between glucose and the free amino group of the valine of hemoglobin A0 -chain. HbA1c is the most important marker for monitoring of the glycemic state in diabetic patients. Different analytical techniques are available for HbA1c determination. The lack of comparability between data from different methods resulted in the need to develop a uniform, scientifically sound, international reference system for HbA1c, i.e. the IFCC reference system. Today, the standardisation of the HbA1c measurement is finally in place, but a clear definition of the clinically allowable total error of measurements is still lacking. Information from biological variation of the analyte can be used to derive these goals. In this study, we systematically reviewed the published studies defining the biological variation of HbA1c to check consistency of available data in order to accurately define analytical goals. All the eight recruited studies showed limitations on the employed analytical methodology, on selected population, and in applying the correct protocol and statistical analyses. In conclusion, there is an urgent need of an accurately designed study to determine biological variability of HbA1c using a traceable and specific assay, appropriate protocol and right statistical derivation of data.

Screening delle infezioni delle vie urinarie mediante un algoritmo decisionale derivato dall’esame chimico-fisico delle urine e dall’analisi automatizzata del sedimento urinario.

T. Suppa*, G. Lobreglio, D. Turco, L. Leo, P. Colazzo, A. Maurantonio

*U.O. Medicina di Laboratorio, Azienda Ospedaliera “Cardinal Panico”, Tricase (LE)

Biochimica Clinica: 2009;33(5):303-05 [Article in italian]

ABSTRACT
Screening of urinary tract infections through a decisional algorithm derived from urinalysis and examination of urinary sediment by an automated imaging system. Many laboratories use urinalysis and microscopic examination of sediment as preventive screening test for bacteriuria and urinary tract infection (UTI). Particularly, an urine sample clinically significant for UTI at the microscopic examination of sediment is characterized by bacteriuria, leucocyturia or leucocytic aggregates, pyuria, and presence of nonsquamous epithelial cells. In our study we evaluated 750 urine samples by an automated digital imaging system for urine sediment examination (IRIS IQ200) and carried out a decisional algorithm through the Logical Analitical Microbiological Flow (FLAM) to show a pathophysiological correlation among different elements identified, i.e. leucocyturia, pyuria, bacteriuria and cellular elements, and to introduce the approach of “clinically significant specimen”, meaning specimen eligible to be appropriately addressed to the urine culture with an effective suspicion of UTI. Comparing FLAM report with urine culture as reference method, we found that 658 (87.7%) samples were concordantly negative, 59 (7.9%) concordantly positive, 8 (1.1%) samples were falsely positive and 25 (3.3%) falsely negative. The screening of UTI through FLAM can decrease microbiological examinations, shorten turnaround time, and reduce work and costs, even if a number of incorrect results was obtained, including 3.3% of false negative results corresponding to a 70.2% sensitivity for the screening test.

Determinazione della olotranscobalamina sierica: valutazione analitica e ruolo in soggetti fumatori asintomatici

R. De Giuseppe, V. Uva, C. Novembrino, R. Accinni, C. Della Noce, D. Gregori, S. Lonati, R. Maiavacca, G. Schiraldi, P. Bonara, F. Bamonti*

*Dipartimento Scienze Mediche, Università degli Studi di Milano, Ospedale Maggiore Policlinico, Mangiagalli e Regina Elena, Fondazione IRCCS, Milano

Biochimica Clinica: 2009;33(5):306-10 [Article in italian]

ABSTRACT
Determination of serum holotranscobalamin: analytical evaluation and role in asymptomatic heavy smokers. Prevalence of subclinical cobalamin (B12) deficiency is higher than expected. Holotranscobalamin (Holo-TC) reflects the actual vitamin status better than total B12. Cobalamin and/or folate deficiency leads to hyperhomocysteinemia, which, like cigarette smoking, is an independent cardiovascular risk factor. We aimed to evaluate a new Holo-TC immunoenzymatic assay (Active B12, Abbott Diagnostics) carried out on an automated analyser (AxSYM, Abbott) and to verify diagnostic utility of Holo-TC in healthy smokers. Analytical performance was assessed by standard procedures. In 61 (35 males, aged 51±10 years) healthy heavy (>20 cigarettes/day) smokers, homocysteine metabolism (homocysteine, folate, B12, Holo-TC) was evaluated using relevant commercial kits on AxSYM analyser. All subjects followed mediterranean diet. Measuring Holo-TC, the inter-assay imprecision (CV) ranged from 3.0% to 7.7%. Mean recovery was 100% (range 93-111%); a good linearity was shown between 8.8 and 143 pmol/L (r2=0.99). The studied subjects showed an altered homocysteine metabolism: mild hyperhomocysteinemia (>10.5 mol/L) was present in 56% (significantly higher in men than in women, P <0.05); serum and erythrocyte folate concentrations were below reference intervals in 15% and 56% of cases, respectively; a decreased B12 was found in 16.4% (significantly lower in men than in women, P <0.05) and Holo-TC was below the cut-off in 29.5% of cases. The AxSYM Holo-TC assay is suitable for routine use. Preliminary data confirm the role of Holo-TC in early detection of B12 deficiency in healthy heavy smokers.

Accuratezza diagnostica di un metodo in chimica secca per la misura della albumina nelle urine nella popolazione generale

M.S. Graziani*, G. Gambaro, L. Mantovani, A. Sorio, T. Yabarek, C. Abaterusso, A. Lupo, P. Rizzotti

*Laboratorio di Analisi Chimico Cliniche ed Ematologiche, Ospedale Civile Maggiore, Azienda Ospedaliera di Verona

Biochimica Clinica: 2009;33(5):311-14 [Article in italian]

ABSTRACT
Diagnostic accuracy of a reagent strip device for assessing urinary albumin excretion in the general population. Albuminuria is a sensitive marker of renal impairment and has been included in a number of studies investigating chronic kidney diseases. This paper is aimed to evaluate the diagnostic performance of a strip test for albumin to creatinine ratio in urine in an epidemiological setting and to compare it with that found in a diabetic population. Urine samples were obtained from 201 consecutive subjects enrolled in a epidemiological study and from 259 type 2 diabetic patients. Urines were examined by the strip test (Clinitek Microalbumin, Siemens Diagnostics) and laboratory methods. Samples were stored under various conditions to assess the analyte stability. When used in the general population, the strip test showed 90% sensitivity and 91% specificity, considering the laboratory method as “gold standard”, saving >80% of subjects from the laboratory measurement, at the expense of 1% rate of false negative and 8% of false positive results. The strip test performed similarly in the general population and in the diabetics. The stability study demonstrated that storage at -20 °C causes a significant decrease in the urinary albumin concentrations. Clinitek Microalbumin strips can be used as screening test in epidemiological settings, since they correctly classify the majority of subjects. Screening with the strip and by confirming positive results with a wet chemistry method can be an efficient strategy for detecting albuminuria in the general population. The recommended temperature for storing urine samples is -80 °C.

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