Multicentre evaluation of a new point-of-care test for the determination of CK-MB in whole blood

BACKGROUND: The point-of-care (POC) test Roche CARDIAC CK-MB is a new assay which has been developed for the existing Roche Cardiac reader system. METHODS: We performed a multicentre evaluation at six sites to assess the analytical performance of the POC CK-MB assay and to compare it with a quantitative laboratory CK-MB assay. RESULTS: Within-series coefficients of variation (CV) resulting from 34 ten-fold measurements with patient samples ranged from 4.3% to 16.4%. Using quality control material, the mean CV values for day-to-day imprecision were 6.5% for the low level control and 8.4% for the high level control. Based upon 847 pairs of values, the mean relative bias of three independently calibrated lots of the POC CK-MB assay ranged from -6% to -11% in method comparisons with the lab CK-MB assay. The mean relative lot-to-lot differences of POC CK-MB were between -2% and +1%. No interference was observed with lipaemic blood (triglyceride concentrations up to 8.1 mmol/L), icteric blood (bilirubin concentrations up to 513 micromol/L), haemolytic blood (haemoglobin concentrations up to 0.12 mmol/L), biotin (up to 30 mg/L) and rheumatoid factor (up to 119 IU/mL), or with 53 standard or cardiological drugs even in toxic concentrations. There was no influence on the results by varying haematocrit values in the range from 21% to 54%. A slight interference with human anti-mouse antibodies type 2 was found. No significant influence on the results with POC CK-MB was found by using sample volumes between 135 and 165 microL. High CK-MB concentrations above the measuring range of POC CK-MB (1-40 microg/L) did not lead to false low results due to potential high-dose hook effect. No significant effect of sample age on recovery occurred up to a sample age of 24 h. No cross-reactivity was found between the POC CK-MB assay and either CK-MM or CK-BB. A substudy with healthy individuals confirmed the reference limits of 3.8 microg/L for females and 6.7 microg/L for males. CONCLUSIONS: The POC CK-MB assay showed a very good analytical performance with an excellent concordance with the calibration and reference laboratory method. It should be therefore suitable for its intended use in POC settings. Clin Chem Lab Med 2008;46:630-8.     

Analytical evaluation of the Dade Behring Dimension RxL automated N-Terminal proBNP (NT-proBNP) method and comparison with the Roche Elecsys 2010.

Methods to quantify B-type natriuretic peptide (BNP) and N-terminal-propeptide (NT-proBNP) in plasma or serum samples are well established. We assessed the analytical performance of the Dimension RxL NT-proBNP method (Dade-Behring). Evaluation of different sample types was carried out. Controls and heparin plasma pools were used to determine the detection limit, precision, and linearity. Sample stability and the effect of interfering substances on the NT-proBNP concentrations were evaluated. Agreement between Dimension RxL and Elecsys 2010 (Roche Diagnostics) NT-proBNP methods was assessed. The influence of age and sex on NT-proBNP concentrations was evaluated in healthy subjects. Heparin plasma should be the matrix of choice. The detection limit was 2.0 ng/L. The total imprecision was 2.6-3.6% for concentrations from 231 to 9471 ng/L; mean NT-proBNP concentrations of 21 and 15 ng/L were associated with coefficients of variation of 9.9% and 14.7%, respectively. The method was linear up to 32,650 ng/L. There was no effect of temperature, freeze-thaw cycles and interfering substances. A bias was detected when Dimension RxL and Elecsys 2010 NT-proBNP methods were compared. Age and sex were significantly and independently related to NT-proBNP concentrations. The Dimension RxL NT-proBNP method, like the Elecsys 2010, is suitable for routine use in the diagnosis of heart failure.     

The brain natriuretic peptide (BNP) precursor is the major immunoreactive form of BNP in patients with heart failure

BACKGROUND: Peptides derived from brain natriuretic peptide (BNP) precursor (proBNP), BNP, and the N-terminal fragment of proBNP (NT-proBNP) are used as biomarkers of heart failure. It remains unclear which forms of these peptides circulate in blood and which forms are measured by assays for these natriuretic peptides. METHODS: To design assays for immunodetection of proBNP, NT-proBNP, and BNP, we used a panel of BNP- and NT-proBNP-specific monoclonal antibodies (MAbs). All MAbs were tested in 2-site combinations in time-resolved fluoroimmunoassays with recombinant or synthetic antigens and plasma from heart failure (HF) patients. ProBNP and related molecules were assayed in HF plasma samples and plasma extracts by means of gel filtration fast protein liquid chromatography (FPLC) before and after protein fractionation on Sep-Pak C18 cartridges. RESULTS: The limits of detection for BNP, proBNP, and NT-proBNP assays were 0.4, 3, and 10 ng/L, respectively. Gel filtration-FPLC studies revealed 1 peak of NT-proBNP (approximately 25 kDa), 1 peak of proBNP (approximately 37 kDa), and 2 peaks of BNP immunoreactivity, a major peak (approximately 37 kDa) for proBNP, and a minor peak (approximately 4 kDa) for BNP. In patient plasma, the molar concentration of NT-proBNP was almost 10 times that of proBNP. The mean proBNP:BNP ratio in patient plasma was 6.3, ranging from 1.8 to 10.8. CONCLUSIONS: ProBNP is the major BNP-immunoreactive form in human blood. The proBNP:BNP ratio in plasma samples is dependent on the methods used for sample handling and for the measurement of the peptides.     

Development and calibration of a new point-of-care test for the determination of NT-proBNP in whole blood

A new point-of-care test for the determination of NT-proBNP in whole blood was developed based on the existing gold-label rapid immunoassay technology of the Roche Cardiac reader system. The novel gold-labelled monoclonal antibody recognizes NT-proBNP at amino acid sequence 27 to 31, the biotinylated polyclonal antibody recognizes sequence 39 to 50. In a model assay based upon the reference method Elecsys proBNP and with an R & D lot of the point-of-care test, this newly selected and developed combination of antibodies showed a very good correlation with the standard Elecsys proBNP assay with correlations of 0.96 or 0.94, respectively. The test was calibrated according to the existing masterlot concept of the Roche CARDIAC tests with Elecsys proBNP as a reference. In a preliminary method comparison with Elecsys proBNP the accuracy of the calibration was confirmed; the bias was between 1 and 6%. Possible reasons of approximately 1% outliers (> +/- 100%) were discussed.     

Head to head comparison of N-terminal pro-B-type natriuretic peptide and B-type natriuretic peptide in patients with/without left ventricular systolic dysfunction

BACKGROUND: Human pro-B-type natriuretic peptide is cleaved into the active B-type natriuretic peptide (BNP) and the inactive fragment NT-proBNP. It is unclear if, similar to BNP, NT-proBNP can be used as a marker of impaired left ventricular (LV) ejection fraction (EF). This study evaluated the analytical performance of both assays to detect LV systolic dysfunction. METHODS: In 72 patients with various degrees of left ventricular systolic dysfunction (LVSD), blood analysis for BNP and NT-proBNP was performed prior to cardiac catheterization, using a point-of-care analyzer (Biosite) and a fully automated laboratory analyzer (Roche-Elecsys), respectively. The within-run and between-run imprecision for BNP and NT-proBNP was calculated. RESULTS: Both markers were able to detect impaired LV EF with the largest area under the receiver-operating-characteristic curve for NT-proBNP (NT-proBNP: 0.851 (0.747-0.924); BNP: 0.803 (0.692-0.887) 95% confidence interval; P = 0.07). A significant correlation was observed between BNP and NT-proBNP (r = 0.9; P < 0.0001). Estimating the within-run imprecision, the coefficient of variance for BNP was 3.14% (n = 20, mean 316 ng/L) to 3.32% (n = 20, mean 820 ng/L) and for NT-proBNP 0.9% (n = 20, mean 4390.8 ng/L) to 1.4% (n = 20, mean 225 ng/L). The between-run imprecision for NT-proBNP ranged between 2.1% (n = 20, mean 224.6 ng/L) and 2% (n = 20, mean 4391 ng/L). Optimal discriminator values for BNP and NT-proBNP were 139 ng/L and 358 ng/L, respectively. However, adjusting the BNP cut-off value to 54 ng/L improved the negative predictive value and sensitivity of the assay. CONCLUSION: Similar to BNP, NT-proBNP is a promising marker in identifying LVSD. Although both assays are reliable and have good analytical performance, their diagnostic cut-off value is dynamic and population-dependent. The slightly wider detection range and the more stable structure of NT-proBNP compared to the BNP assay suggest that NT-proBNP could play an additional role in the evaluation of patients with LV systolic dysfunction.     

Prohormone brain natriuretic peptide (proBNP), BNP and N-terminal-proBNP circulating levels in chronic hemodialysis patients. Correlation with ventricular function, fluid removal and effect of hemodiafiltration

BACKGROUND: Brain natriuretic peptide (BNP), N-terminal proBNP (NT-proBNP) and to a lesser extent prohormone proBNP are recognized as biochemical markers of left ventricular dysfunction. In renal failure, interpretation of natriuretic peptide remains unclear, as natriuretic peptide levels may be not only be dependent on cardiac function and dimensions but also on renal function, fluid volume and removal by dialysis procedure including hemodiafiltration (HDF). The purpose of this study was (i) to assess BNP, NT-proBNP and proBNP levels and their correlation with clinical and echocardiographic data in chronic hemodialysis patients, and (ii) to investigate basal level alteration following HDF. METHODS: Baseline clinical and echocardiographic parameters were collected in 31 dialysis patients without evidence of cardiac failure. Pre- and post-HDF BNP, NT-proBNP and proBNP concentrations were measured. Correlations between echocardiographic measurements and basal circulating peptides, between changes in peptide values and changes in fluid volume after HDF were investigated. RESULTS: Baseline plasmatic levels were elevated (BNP=517+/-840 pg/mL, NT-proBNP=5340+/-6132 pg/mL and proBNP=3569+/-4683 pg/mL) and correlated with left auricular diameter and left ventricular mass index. HDF session induced a significant decrease of 39%, 59% and 36% for BNP, NT-proBNP and proBNP levels, respectively. This decrease was not correlated to post-HDF fluid removal or weight decrease. Correlation between BNP and proBNP was stronger (r(2)=0.88) than between NT-proBNP and proBNP (r(2)=0.54). CONCLUSIONS: Despite their elimination, BNP, NT-proBNP and proBNP could be potential markers of left ventricular remodeling in chronic renal failure patients on hemodialysis. According to these results, their cut-off values, however, need to be re-evaluated.     

Multicenter analytical performance evaluation of the Elecsys proBNP assay.

The purpose of this multicenter study was to evaluate the technical performance of the automated Elecsys proBNP (brain natriuretic peptide) assay, which is indicated as an aid in the diagnosis of individuals suspected of having congestive heart failure. The Elecsys proBNP assay is an electrochemiluminescent immunoassay employing two polyclonal NT-proBNP-specific antibodies in a sandwich test format. The study was performed on the three Elecsys analyzers (E 1010, E 2010, and E 170) at eight different sites world-wide. Within- and total precision were < or = 3%, with total precision slightly higher on the Elecsys E 170 instrument with multiple modules. Reproducibility among sites and platforms was < 5%. Precision at particularly low NT-proBNP concentrations was assessed down to approximately 25 pg/ml with CVs of 12.6% at 29.2 pg/ml and 9.6% at 38.5 pg/ml for the Elecsys 1010/2010 and E 170, respectively. Linearity was evaluated up to 25,000 pg/ml with a sample-based non-linear response observed with recoveries of < 90% for proBNP concentrations < 10,000 pg/ml. Slopes ranged between 0.92 and 1.02 and intercepts from -5.3 to 10.4 pg/ml (r > or = 0.998) among the three types of analyzers. Slopes were 4.95 and 4.53 in comparison to the Biosite Triage and Shionogi BNP assays. There was no assay interference, and no effect of barrier gels, tube composition, or freeze-thaw. NT-proBNP concentrations in EDTA plasma were up to 10% lower than in serum or heparinized plasma and the analyte was stable at 4 degrees C for up to 72 hours (the maximum time tested). There was no circadian rhythm in normal subjects or congestive heart failure patients and there was no effect of drawing position. In summary, the Elecsys proBNP assay exhibits good technical performance and is suitable for use in routine clinical laboratories to aid in the diagnosis of congestive heart failure.     

Large-scale performance evaluation of Accu-Chek inform II point-of-care glucose meters

Background: The aim of this study was to report the experience of large-scale performance evaluation of 238 Accu-Chek Inform II point-of-care (POC) glucose meters in a single medical setting.

Methods: The repeatability of 238 POC devices, the within-site imprecision of 12 devices, and the linearity of 49 devices were evaluated using glucose control solutions. The glucose results of 24 POC devices and central laboratory were compared using patient samples.

Results: Mean concentration of control solutions was 2.39?mmol/L for Level 1 and 16.52?mmol/L for Level 2. The pooled repeatability coefficient of variation (CV) of the 238 devices was 2.0% for Level 1 and 1.6% for Level 2. The pooled within-site imprecision CV and reproducibility CV of the 12 devices were 2.7% and 2.7% for Level 1, and 1.9%, and 1.9% for Level 2, respectively. The test results of all 49 devices were linear within analytical measurement range from 1.55–31.02?mmol/L. The correlation coefficient for individual POC devices ranged from 0.9967–0.9985. The total correlation coefficient for the 24 devices was 0.998.

Conclusions: The Accu-Chek Inform II POC blood glucose meters performed well in terms of precision, linearity, and correlation evaluations. Consensus guidelines for the large-scale performance evaluations of POC devices are required.     

健康人群血清NT-proBNP浓度水平评估

目的对健康人群N端-前脑钠索（NT-proBNP）度水平进行评估。方法采集103个健康受试者的血清标本，应用罗氏2010电化学发光免疫分析仪测定血清NT-proBNP浓度，采用SPSS11．5软件进行分析，探讨20—40岁年龄段健康人群中的NT-proBNP参考值范围。结果研究结果显示在该年龄段参考值的范围：男性组为〈50．7ng／L，女性组为〈79．3ng／L.男性组中位数为17．5ng／L，女性组中位数为35．6ng／L。女性组明显高于男性组（P〈0．05）。结论建立20-40岁年龄段健康受试者的NT-proBNP正常参考值范围。     

N末端B型脑钠肽前体在心力衰竭中的诊断和预后价值

【目的】探讨N末端B型脑钠肽前体（NT-proBNP）对心力衰竭（简称心衰）的诊断意义以及对心衰的预后价值。【方法】设心衰组65例,对照组92例,测定血浆NT—ProBNP、左室射血分数（LVEF）,左室舒张末内径（LVDd）及评价NYHA心功能分级。出院复查一次,随访病人3个月内的再入院率。【结果】①心衰组NYHAⅡ、Ⅲ、Ⅳ级与对照组的血浆lnNT-proBNP水平两两比较有统计学差异（P〈0．01）,心功能越差血浆lnNT—proBNP水平显著升高。②lnNT—proBNP（取自然对数ln）与LVDd呈正相关（r=0．423,P〈0．01）,lnNT—proBNP与LVEF呈负相关（r=-0．407,P〈0．01）。③NT—proBNP诊断心衰的ROC曲线显示,当cut—Off值定为459pg／mL时,正确诊断指数最高（0．578）,此时敏感度76．7％,特异度100％。④心衰患者出院时NT—proBNP升高组45例,正常组20例。升高组3个月内因心衰再住院者20例（44．4％）,正常组2例（10％）。【结论】NT—proBNP是诊断心衰的可靠指标,与心衰的严重程度密切相关,动态观察NT—proBNP变化水平可有效地判断心衰患者的预后。     

胸水及血浆NT—proBNP对老年患者心源性胸腔积液的诊断价值

目的：研究老年心力衰竭（HF）急性加重期合并胸水患者的胸水与血浆NT—proBNP相关性和诊断价值。方法：选择2007年1月-2008年12月入住本院的老年胸腔积水患者60例,平均年龄（81．0±8．03）岁。取胸腔积水行生化、细菌学、细胞学检查NT—proBNP水平测定。分析老年患者胸腔积水和血浆NT—proBNP水平对诊断心源性胸腔积液的应用价值。结果：老年患者胸腔积水和血浆NT—proBNP水平无显著差异[（6537．1±10299．6）：（6085．6±10147．5）ng／L]（P〉0．05）,两者呈线性正相关（R=0．955,P〈0．05）。在诊断心源性胸腔积液方面,胸腔积水NT—proBNP cutoff值为1305．0ng／L,血浆NT—proBNP cutoff值为1723．0ng／L。结论：老年患者胸水和血浆NT—proBNP水平可以作为诊断心源性胸腔积液的一项辅助性检查指标。     

The changes in NT-proBNP plasma concentrations during dialysis are highly dependent of the dialysis membrane ultrafiltration coefficient

BACKGROUND: NT-proBNP is a powerful marker with diagnostic and pronostic value for heart failure. It is of particular interest in patients with end-stage renal disease who are at high risk for heart failure. The aim of this study was to investigate the effect of hemodialysis on plasma NT-proBNP concentrations. METHODS: NT-proBNP concentration was measured in 67 patients before and after hemodialysis. RESULTS: In the 20 patients dialyzed with a membrane whose ultrafiltration coefficient was below or equal to12, NT-proBNP concentration was comparable after and before dialysis (16611+/-21024 vs. 15216+/-19027 pg/ml, NS). At the opposite, in the 47 patients dialyzed with a membrane whose ultrafiltration coefficient was above or equal to 40, NT proBNP concentration was 35% lower after dialysis compared to before dialysis (11983+/-21819 vs. 18574+/-31862 pg/ml, p<0.0001). CONCLUSIONS: In patients dialyzed with a membrane whose ultrafiltration coefficient is high, dialysis is likely to decrease results by one third. Thus sampling blood before dialysis in hemodialyzed patients appears as the best time to stratify the cardiovascular risk in these patients.     

Analysis of circulating forms of proBNP and NT-proBNP in patients with severe heart failure

BACKGROUND: The specific forms of pro-B-type natriuretic peptide (proBNP) that occur in human blood are not yet clear. We demonstrated the presence of several proBNP forms in human plasma with a new affinity chromatography method that can be used in combination with nano-liquid chromatography electrospray ionization tandem mass spectrometry (nano-LC-ESI-MS/MS). METHODS: For affinity chromatography, we coupled Fab' fragments of polyclonal sheep antibodies specific for N-terminal proBNP (NT-proBNP) epitope 1-21 to silica beads. We connected a column (10 mm x 0.8 mm inner diameter) packed with these beads to a trypsin reactor and used a preconcentrator in combination with a fritless nanospray column to perform MS analyses of proBNP forms in preextracted and non-preextracted samples of plasma from patients with severe heart failure (HF). We used Western blotting in deglycosylation experiments to confirm the shifts in proBNP and NT-proBNP masses. RESULTS: Tandem MS experiments demonstrated the presence of both NT-proBNP and circulating proBNP in preextracted samples of plasma from patients with severe HF, and Western blotting analyses revealed 2 bands of approximately 23 kDa and 13 kDa that shifted after deglycosylation to positions that corresponded to the locations of recombinant proBNP and synthetic NT-proBNP. CONCLUSIONS: We obtained clear evidence for circulating proBNP in patients with severe HF and provided the first demonstration of O-glycosylation of NT-proBNP. The higher molecular masses for NT-proBNP and proBNP observed in the Western blotting analyses than those expected from calculations can be explained by O-glycosylation of these peptides in vivo.     

B-type natriuretic peptide concentrations predict the progression of nondiabetic chronic kidney disease: the Mild-to-Moderate Kidney Disease Study

BACKGROUND: Plasma concentrations of B-type natriuretic peptide (BNP) and N-terminal proBNP (NT-proBNP) are diagnostic and prognostic biomarkers of heart failure and are also increased in patients with chronic kidney disease (CKD). We examined the relevance of BNP and NT-proBNP as predictors of CKD progression. METHODS: Of 227 nondiabetic patients with mild-to-moderate renal insufficiency, 177 patients ages 18-65 years were followed in a prospective multicenter cohort study for a period of < or = 7 years. CKD progression was assessed by recording renal endpoints, defined as doubling of baseline serum creatinine or end-stage renal disease (ESRD) requiring renal replacement therapy. RESULTS: BNP and NT-proBNP were significantly higher among 65 patients who reached the combined renal endpoint than among the 112 who did not [median (interquartile range) 61 (27-98) ng/L vs 39 (20-70) ng/L, P = 0.023, for BNP; 320 (117-745) ng/L vs 84 (44-176) ng/L, P <0.001, for NT-proBNP)]. Each increment of 1 SD in log-transformed BNP and NT-proBNP increased the risk of CKD progression by hazard ratios of 1.38 (95% CI 1.09-1.76, P = 0.009) and 2.28 (1.76-2.95, P <0.001), respectively. After adjustment for other established prognostic factors of CKD progression, NT-proBNP but not BNP remained a significant independent predictor of the combined renal endpoint. CONCLUSIONS: Increased BNP and NT-proBNP concentrations indicate an increased risk for accelerated progression of CKD to ESRD and may prove to be valuable biomarkers for the assessment of prognosis in patients with CKD.     

Two-center clinical evaluation of a new automated fluorometric immunoassay for the quantitative analysis of total betaeta-human chorionic gonadotropin

OBJECTIVES: This study evaluated the quantitative total betahCG assay on the Stratus CS point-of-care instrument at two medical centers. DESIGN AND METHODS: Analytical sensitivity, linearity, within-run and total imprecision, interferences, dilution recovery, method comparison (Dimension RxL), comparison of matched heparinized whole blood and plasma samples, and determination of the normal reference interval were studied. RESULTS: Analytical sensitivity was <0.5 IU/L. The assay's linear range was 0 to 1250 IU/L; the clinical reportable range was up to 50,000 IU/L. Within-run imprecision (CV) at both low (<20 IU/L) and elevated (760 IU/L) betahCG concentrations were <4%. Total imprecision for three QC levels and two pools were <4%. Method comparison showed Stratus CS betahCG = 0.98 +/- 0.01* Dimension RxL hCG -0.11 +/- 2.69 (n = 136; r = 0.996; Sy/x = 27.7). Matched heparinized whole blood/plasma sample-comparison showed: whole blood = 1.05*Plasma + 0.37 +/- 1.29 (n = 41; r = 1.000; Sy/x = 7.57). Mean dilution recovery was 99% (range: 95% to 103%). None of the 52 drugs tested, lipemia, icterus, hemolysis, LH, FSH, TSH, hGH or prolactin represented a significant interference with the assay. Reference intervals were <0.5 IU/L for males (n = 123) and <3.0 IU/L for nonpregnant females (n = 120). CONCLUSIONS: The Stratus CS betahCG test offers the advantage of quantitative measurement of total betahCG in whole blood at the point of care and is suitable for clinical use.     

High intraindividual variation of B-type natriuretic peptide (BNP) and amino-terminal proBNP in patients with stable chronic heart failure

BACKGROUND: Plasma B-type natriuretic peptide (BNP) and N-terminal proBNP (NT-proBNP) are promising markers for heart failure diagnosis, prognosis, and treatment. Insufficient data on the intraindividual biological variation (CV(i)) of BNP and NT-proBNP hamper interpretation of changes in concentration on disease progression or treatment optimization. We therefore investigated CV(i) values in stable heart failure patients. METHODS: We recruited 43 patients with stable chronic heart failure living in Curacao (22 males, 21 females; median age, 63 years; range, 20-86 years; New York Heart Association classes I-III). Samples were collected for within-day CV(i) (n = 6; every 2 h starting at 0800), day-to-day CV(i) (n = 5; samples collected between 0800 and 1000 on 5 consecutive days), and week-to-week CV(i) (n = 6; samples collected between 0800 and 1000 on the same day of the week for 6 consecutive weeks). NT-proBNP (Roche) and BNP (Abbott) were measured by immunoassay. RESULTS: Median (range) concentrations were 134 (0-1630) ng/L (BNP) and 570 (17-5048) ng/L (NT-proBNP). Analytical variation, week-to-week CV(i), and reference change values were 8.4%, 40%, and 113% (BNP), and 3.0%, 35%, and 98% (NT-proBNP). Week-to week CV(i)s were inversely related to median BNP concentrations. Week-to week CV(i)s for BNP were 44% (BNP < or =350 ng/L) and 30% (BNP >350 ng/L). Both BNP and NT-proBNP increased between 0800 and 1000. Median NT-proBNP/BNP ratios were inversely related to median BNP concentrations. CONCLUSIONS: The high CV(i)s hamper interpretation of changes in BNP and NT-proBNP concentrations and may partly explain their poor diagnostic values in chronic heart failure. Easily modifiable determinants to lower CV(i) have not been identified. The value of BNP and NT-proBNP for chronic heart failure diagnosis, and especially for follow-up and treatment optimization of individuals, remains largely to be established.     

Capability of B-type natriuretic peptide (BNP) and amino-terminal proBNP as indicators of cardiac structural disease in asymptomatic patients with systemic arterial hypertension

BACKGROUND: The aim of the present study was to prospectively evaluate the diagnostic utility of B-type natriuretic peptide (BNP) and amino-terminal proBNP (NT-proBNP) measurements for the detection of cardiac structural disease in asymptomatic patients with systemic arterial hypertension and to test the hypothesis that the 2 analytes are equally useful in this clinical setting. METHODS: We studied a consecutive series of 149 asymptomatic patients referred for echocardiographic evaluation of the cardiac effects of systemic arterial hypertension. Diagnosis of cardiac structural disease was based on the presence of systolic or diastolic dysfunction, left atrial dilatation, left ventricular dilatation or hypertrophy, pulmonary hypertension, and wall motion or valvular abnormalities. Blood concentrations of BNP and NT-proBNP were measured by 2 commercially available assays (Abbott AxSYM and Roche Elecsys, respectively). Diagnostic accuracies of BNP and NT-proBNP were assessed by ROC curve analysis. Areas under the curves were compared by analysis of equivalency. RESULTS: In distinguishing between hypertensive patients with cardiac structural disease (n = 118) and hypertensive patients without (n = 31), areas under the curves were 0.740 (95% confidence interval, 0.662-0.808) for BNP and 0.762 (0.685-0.828) for NT-proBNP and were significantly equivalent (P = 0.015). Cutoff values with a 90% sensitivity for cardiac structural disease were 17 ng/L for BNP and 39 ng/L for NT-proBNP, with 29% and 32% specificity, respectively. CONCLUSIONS: BNP and NT-proBNP have similar capabilities for detecting cardiac structural disease in asymptomatic patients with systemic arterial hypertension. However, in the setting evaluated, a screening strategy relying on measurement of BNP or NT-proBNP may be of limited value because of the low specificity at the selected cutoff values.     

Analytical evaluation of the Optium Xido blood glucose meter.

BACKGROUND: The main prevention of chronic diabetic complications is maintaining near normoglycemia. In this study, evaluation of analytical performance of the Optium Xido blood glucose meter designed for patients' self-monitoring of glycemia was carried out. METHODS: Glucose concentrations were measured in 118 EDTA blood samples using the Xido glucose meter and the GOD/PAP method on a Modular P clinical analyzer. The results obtained were used for the assessment of accuracy, precision and linearity. Performance of the Xido glucose meter was also assessed using four different reagent strip lots, and the between-lot variation was calculated. RESULTS: The within-run imprecision coefficient of variation (CV) amounted to 4.2%. Good response linearity was found in glucose concentrations of 31-444 mg/dL (1.7-24.7 mmol/L). In the concentration range studied, the glucose meter error was 5.14% and the linear regression equation was y=0.91x+6.2, (r=0.984). The Passing-Bablok agreement test indicated good concordance of results. However, for glucose concentrations<100 mg/dL (5.6 mmol/L) (n=69) the error was 6.82% with regression equation y=0.86x+5.9 (r=0.757). Between-lot differences amounted to 0.7%-18.2%. CONCLUSIONS: The Xido glucose meter has good precision and accuracy when compared to the laboratory method and meets the quality recommendations of the National Committee of Clinical Laboratory Standards (NCCLS, currently the Clinical Laboratory Standards Institute), the National Academy of Clinical Biochemistry (NACB) and the International Organization for Standardization (ISO). However, between-lot variability may result in differences between day-to-day results when the device is continuously used. Therefore, the validation of new lots of reagent strips with a laboratory method is recommended.     

氨基端前脑钠肽在不同年龄心力衰竭中的界值选择

目的 探讨氨基端前腩钠肽(NT-proBNP)在不同年龄段评价心功能的界值选择.方法 48例心功能不全(NYHA Ⅰ-Ⅳ)患者来自复旦大学附属中山医院急诊科.入选标准:有器质性心脏疾病基础;心功能(NYI-IA)Ⅰ-Ⅳ级.所有患者均排除急性冠脉综合征、持续性房颤、肺气肿、肺栓塞、慢性肾功能不全、贫血、甲状腺功能异常以及肿瘤患者.按年龄是否超过75岁分两组,高龄组(n=18)和非高龄组(n=30),并按NYHA标准进行心功能分级.测定患者血NT-proBNP,分析高龄组和非高龄组心功能分级与NT-proBNP之间的关系,分析利用心功能分级参考值作为鉴别急性心源性呼吸困难界值的可行性.计量数据以均数±标准差表示.两组间差异的显著性分析用t检验,多组间差异的显著性分析用方差分析.P＜0.05具有统计学意义.数据分析使用统计软件SPSS11.0.结果 研究对象的NT-proBNP与心功能分级、左心室射血分数(LVEF)关系密切.非高年龄组的NT-proBNP值较高龄组高,在心功能Ⅱ、Ⅳ级水平,两组NT-proBNP相比,差异具有统计学意义[(407±277)vs.(1358±967),P＜0.05;(727±1342)vs.(9031±2363),P＜0.01].在心功能Ⅲ级水平,尽管高龄组的NT-proBNP值更高,但组间没有显著性差异(P=0.067).NT-proBNP检测严重症状性心衰(NYHAⅢ-Ⅳ级)的受试者工作特性曲线下面积为0.958,界值525 pg/ml,敏感性100%,特异性76%;界值1911pg/ml,敏感性73%,特异性96%.高龄患者NT-proBNP检测严重症状性心衰(NYHA Ⅲ-Ⅳ级)的受试者工作特性曲线下面积为0.922,界值849 pg/ml,敏感性100%,特异性57%;界值2990 pg/ml,敏感性81%,特异性100%.结论 心功能分级的NT-proBNP参考值存在年龄组间差异.笔者建议对高龄患者选择更高的NT-proBNP参考值评价心功能状况,选择更高的界值鉴别急性心源性呼吸困难.