Graziella Bonetti

Association between Apolipoprotein(a) phenotypes and coronary heart disease at a young age

OBJECTIVES The purpose of this study was to investigate lipoprotein(a) [Lp(a)] levels and apolipoprotein(a) [apo(a)] phenotypes in relation to age of onset of coronary heart disease (CHD). BACKGROUND Although Lp(a) levels have been extensively analyzed in relation to age of CHD, apo(a) phenotypes have not. METHODS Three hundred and thirty-five consecutive CHD patients were enrolled and grouped according to their age of CHD onset (<45 years; 45 to 54 years; > or = 55 years). RESULTS In each patient group Lp(a) levels were higher than in an age-matched control group, but among the patient groups no differences in Lp(a) levels were observed. Apolipoprotein(a) phenotype distributions showed significant differences between patients and age-matched control subjects. Among the patient groups the difference in percentage of subjects with two apo(a) isoforms of low molecular weight (MW) was highly significant (p < 0.001). Multivariate analysis showed that apo(a) phenotypes were the best predictors of early CHD (p < 0.000001). The age-specific odds ratios (ORs) of the presence of at least one apo(a) isoform of low MW for CHD declined with age; in particular apo(a) phenotypes had their highest predictive value in younger persons (OR: 14.62). The OR for the presence of two isoforms of low MW/presence of only isoforms of high MW was 40.88 in the younger age group, 27.17 in age group of 45 to 54 years and 15.83 in the older age group. CONCLUSIONS The present article reports the first evidence of a strong independent association of apo(a) phenotypes with the age of onset of CHD. Thus, if our data are confirmed by larger studies, apo(a) phenotypes might be used together with Lp(a) levels as powerful genetic markers in assessing the actual risk of developing CHD at a young age.

Association of lipoprotein(a) levels and apolipoprotein(a) phenotypes with coronary heart disease in patients with essential hypertension

Background Besides hypertension, several cardiovascular risk factors can play a role in the development of coronary heart disease (CHD) in hypertensive patients. Lipoprotein(a) [Lp(a)] is an important and independent cardiovascular risk factor, but its role in the development of CHD in hypertensives has not been studied. Objective To investigate whether or not Lp(a) levels and isoforms of apolipoprotein(a) [apo(a)] are predictors of CHD in patients with essential hypertension. Methods Lp(a) levels and apo(a) polymorphism were evaluated in 249 patients with essential hypertension, in 142 non-hypertensive patients with CHD and in 264 healthy controls. Results Hypertensives with CHD (n = 61) had Lp(a) levels [19 (range 0.5–73.5) versus 7 mg/dl (range 0–83.5), P < 0.001] and a percentage of apo(a) isoforms of low (< 655 kDa) relative molecular mass (RMM, 59.2 versus 25.9%, P < 0.001) higher than did those without CHD (n = 188). Moreover, there were more subjects with at least one apo(a) isoform of low RMM in the subgroup of patients with CHD than there were in that of those without CHD (80.3 versus 30.8%, P < 0.001). Lp(a) levels and apo(a) polymorphism did not differ significantly between hypertensive and non-hypertensive patients with CHD. Stepwise regression analysis indicated that high Lp(a) levels (P = 0.002073) and particularly the presence of at least one apo(a) isoform of low RMM (P < 0.000001) are strong predictors of CHD in hypertensive patients. Conclusions Our data show that high Lp(a) levels and the presence of at least one apo(a) isoform of low RMM are strong and independent genetic risk factors for CHD in hypertensive patients. These findings suggest that Lp(a) and apo(a) isoforms should be assessed together with other cardiovascular risk factors to establish the overall CHD risk status of each hypertensive patient.

Apolipoprotein(a) Phenotypes and Their Predictive Value for Coronary Heart Disease: Identification of an Operative Cut-Off of Apolipoprotein(a) Polymorphism

Background Apolipoprotein(a) isoforms of low-molecular weight are associated with coronary heart disease. However, because of the high number of apolipoprotein(a) isoforms, it is difficult to assess the cardiovascular risk linked to the apolipoprotein(a) gene of a subject; indeed a cut-off of apolipoprotein(a) polymorphism has not been established. The aim of this investigation was to identify an ‘operative’ cut-off that discriminates apolipoprotein(a) isoforms associated with high genetic risk for coronary heart disease. Methods Two hundred and fifty-one patients with coronary heart disease and 284 controls were recruited. Apolipoprotein(a) isoforms were detected using a high-resolution phenotyping method. Results Twenty-seven apolipoprotein(a) isoforms with apparent molecular weight varying from 280 to 820 kDa were identified. Several cut-offs of apolipoprotein(a) polymorphism were used in order to compare the frequencies of apolipoprotein(a) isoforms of low and high molecular weight between patients and controls: The cut-off between 640 and 655 kDa had the highest χ2 (130.40). Even when possible differences in apolipoprotein(a) phenotypes (subjects with at least one isoform of low molecular weight and subjects with only isoforms of high molecular weight) were assessed, the same cut-off showed the highest χ2 (122.47). Multivariate analysis showed that apolipoprotein (a) isoforms had the greatest predictive value for coronary heart disease (F value= 107.0720), when the cut-off between 640 and 655 kDa was used. Conclusions The cut-off between 640 and 655 kDa appears to be the most efficient in identifying subjects at high cardiovascular risk linked to apolipoprotein(a) gene, since this cut-off discriminates apolipoprotein(a) isoforms expressing a greater risk for coronary heart disease. J Cardiovasc Risk 5: 37-42

Lipoprotein(a) plasma concentrations, apolipoprotein (a) polymorphism and family history of coronary heart disease in patients with essential hypertension.

Aim The purpose of the study was to investigate lipoprotein (a) (Lp(a)) levels and apolipoprotein (a) (apo(a)) phenotypes, and their relationship with a family history of coronary heart disease (CHD) in patients with essential hypertension (EH). Methods One hundred and eight newly diagnosed patients with mild to moderate EH and 159 controls were studied. Lp(a) levels were determined with an ELISA method. Apo(a) isoforms were identified by a capillary immunoblotting technique. Results Lp(a) levels and frequency distribution of apo(a) isoforms did not show significant differences between patients and controls. Lp(a) levels in hypertensives with a family history of CHD were significantly higher than in those without a family history of CHD (P <0.01). Hypertensives with a family history of CHD showed significantly different frequencies of apo(a) isoforms to those without a family history of CHD (P <0.05). In EH patients with a family history of CHD, apo(a) isoforms of low molecular weight (MW) had a higher prevalence (62.6%), while in hypertensives without a family history of CHD, apo(a) isoforms of high MW were prevalent (81.6%); the difference between the two subgroups was significant (P <0.001). Multivariate analysis showed that both Lp(a) levels and apo(a) isoforms of low MW are significant variables in distinguishing between the subgroups. Conclusions Lp(a) levels and apo(a) phenotypes do not differ between hypertensives and controls. High Lp(a) levels and apo(a) isoforms of low MW are strongly associated with a family history of CHD in hypertensives. The quantification of Lp(a) levels and the characterization of apo(a) phenotypes may be used for assessment of familial predisposition to CHD in hypertensives.

Which sample tube should be used for routine glucose determination

BACKGROUND Glucose is one of the most frequently requested analytes in clinical laboratory. Blood glucose analysis is affected from in vitro glycolysis. In order to determine the most suitable blood collection tube for this purpose we have compared different tubes: sodium fluoride, lithium heparin, sodium fluoride/citrate buffer containing tubes and serum with clot activator tube for the measurement of glucose when the tube has been kept at room temperature (RT) for up to 4h. METHODS Venous blood was collected from 49 healthy volunteers into Sarstedt S-Monovettes for glucose analysis. Reference plasma glucose was determined in a lithium heparin tube and immediately placed in an ice/water slurry. Within 10min it was centrifuged at 4°C and plasma was separated from the blood cells. Samples have been preserved at RT for 1, 2 and 4h after drawing. Glucose has been determined using a hexokinase method. RESULTS Glucose levels tested in a serum with clot activator tube, in lithium heparin and in sodium fluoride/sodium EDTA tubes when compared with lithium-heparin reference plasma did not meet the desirable bias for glucose (±1.8%) when kept at RT for up to 4h. GlucoEXACT tubes, when corrected by the Sarsted recommended factor of 1.16, showed a mean (95% CI) bias of +0.96% (0.45-1.47) at 1h, +1.40% (0.88-1.93) at 2h and +0.95% (0.44-1.46) at 4h, reaching the analytical goal for the desirable bias. CONCLUSIONS Samples collected into GlucoEXACT tubes containing sodium fluoride/citrate buffer liquid mixture are equivalent to those collected in reference plasma tubes avoiding glycolysis completely and within a 4h delay in plasma separation.

Lipoprotein(a), Apolipoprotein(a) Polymorphism, and Insulin Treatment in Type II Diabetic Patients

et al. that this problem does not concern pumps in general. We also agree that the new adaptor for the H-Tron V-100, which is equipped with two small holes and can be closed with a red plug, should eliminate these problems as long as the pump is used according to the manufacturers specific instructions. We also fully support the recommendation suggested by Prendergast et al. to use the plug for the adaptor holes only when watertightness is needed (in the bath or shower) instead of removing it only when pressure problems are expected. When such instructions are followed, the H-Tron V-100 is at least an equal alternative to other pumps in the market.

Glucose sampling: importance of citrate.

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The new Greiner FC-Mix tubes equal the old Terumo ones and are useful as glucose stabilizer after prolonged storage of samples

Introduction The aim of our study is to compare new Greiner tubes containing granulated citrate buffer with the Terumo ones and to verify if they are suitable for glucose stabilization after prolonged storage. Materials and methods In Study 1, blood was collected in two Terumo and two Greiner tubes from 40 healthy volunteers. Samples were stored at room temperature (RT) for 1 and 2 hours, respectively. Comparison was made by Deming regression. In Study 2, glucose was measured in a reference tube (N = 50), according to the ADA-NACB guidelines and in aliquots of Greiner samples maintained un-centrifuged at RT for 1, 2, 4 (N = 50) and 24, 48, 72 hours (N = 35). Results There were insignificant mixed biases between the Terumo and Greiner tubes. Compared to reference (5.3 mmol/L), glucose concentration in the new tubes was 5.4 (P < 0.05), 5.4 (P < 0.05), 5.3 (P = 0.265), 5.2 (P = 0.156), 5.3 (P < 0.05) and 5.2 (P < 0.05) mmol/L after 1, 2, 4, 24, 48 and 72 hours at RT, respectively. There was no biological difference between any of the time points up to 48 h (bias < ± 1.95%). Conclusions The study shows that the new tubes perform equally well as the Terumo ones and ensure glucose stabilization up to 48 h as well as permit to create a link between the previous studies demonstrating the clinical utility of granulated citrate buffer and the future ones.

Multicenter evaluation of an enzymatic method for glycated albumin

BACKGROUND The use of glycated albumin (GA) has been proposed as an additional glycemic control marker particularly useful in intermediate-term monitoring and in situation when HbA1c test is not reliable. METHODS We have performed the first multicenter evaluation of the analytical performance of the enzymatic method quantILab Glycated Albumin assay implemented on the most widely used clinical chemistry analyzers (i.e. Abbott Architect C8000, Beckman Coulter AU 480 and 680, Roche Cobas C6000, Siemens ADVIA 2400 and 2400 XPT). RESULTS The repeatability of the GA measurement (expressed as CV, %) implemented in the participating centers ranged between 0.9% and 1.2%. The within-laboratory CVs ranged between 1.2% and 1.6%. A good alignment between laboratories was found, with correlation coefficients from 0.996 to 0.998. Linearity was confirmed in the range from 7.6 to 84.7%. CONCLUSION The new enzymatic method for glycated albumin evaluated by our investigation is suitable for clinical use.

Raccomandazioni per l’ottimizzazione della fase pre-analitica per una corretta determinazione della glicemia in ambito diabetologico

RiassuntoLa diminuzione del glucosio nelle provette è tempo-dipendente dopo il prelievo e può causare artificialmente bassi valori di glicemia se la glicolisi non è appropriatamente inibita dall’ uso corretto dell’anticoagulante. In questo lavoro abbiamo fatto una accurata revisione della letteratura sul possibile uso del citrato assieme al sodio EDTA e al sodio fluoruro. Noi concludiamo che, per lo screening e la diagnosi del diabete mellito, incluso il diabete gestazionale, il glucosio dovrebbe essere determinato nel plasma usando la sopra menzionata mistura sia allo stato solido che allo stato liquido (in questo caso deve essere applicato il corretto fattore di conversione numerico). Per la misura del glucosio in pazienti con diabete già diagnosticato per il monitoraggio in follow up, provette con litio eparina possono essere usate ma la separazione del plasma delle essere rapidamente condotta. In alternativa possono essere usate provette per siero con acceleratore della coagulazione e gel separatore.SummaryThe time-dependent decrease of glucose in tubes after venipuncture may cause artificially lower values, if glycolysis is not appropriately inhibited by the correct anticoagulant. In this work we have extensively reviewed the current literature about the possible use of citrate buffer together with sodium EDTA and sodium fluoride. We conclude that, for screening and diagnosis of diabetes mellitus, including gestational diabetes, glucose has to be determined in plasma by using the above mentioned ternary mixture either as solid than in liquid state (in this case the correct numerical conversion factor has to be employed). For the measurement of glucose in patients with already known diabetes and following monitoring, lithium heparin tubes may be used providing that plasma separation should be rapidly performed. Alternatively, serum-separating tubes with particles promoting rapid clotting could also be employed.