Effect of anticoagulants and storage temperatures on stability of plasma and serum hormones

OBJECTIVES: To determine the effect of different anticoagulants and storage conditions on the stability of hormones in plasma and serum. DESIGN AND METHODS: Human blood samples were collected from volunteers into EDTA, lithium heparin, sodium fluoride/potassium oxalate, or tubes without anticoagulant, plasma and serum left at -20 degrees C, 4 degrees C or 30 degrees C for 24 and 120 hours then assayed for ACTH, aldosterone, alpha-subunit, AVP, CRH, C-peptide, estradiol, FSH, glucagon, GH, IGF-1, IGFBP-3, insulin, leptin, LH, PPP, PTH, prolactin and VIP, or at room temperature for 0 to 72 hours (BNP, NT-BNP)(n = 6 per condition). RESULTS: The anticoagulant altered the measured concentrations for 9 hormones when compared to EDTA. All hormones except ACTH were stable for > 120 hours in EDTA or fluoride at 4 degrees C, but only 13 hormones were stable in all anticoagulants. At 30 degrees C, 8 hormones were stable for > 120 hours in EDTA, and 3 hormones in all anticoagulants. BNP and NT-BNP were stable for < 24 hours when stored in EDTA or heparin at room temperature. DISCUSSION: Storage of samples in EDTA plasma at 4 degrees C is suitable for most hormones (except ACTH) for up to 120 hours.     

Assay values for thiamine or thiamine phosphate esters in whole blood do not depend on the anticoagulant used

We compared the whole blood, plasma, and erythrocyte (red blood cell (RBC)) concentrations of thiamine and thiamine phosphate esters in the presence of heparin or EDTA as anticoagulants. Three blood specimens were collected from each of 24 healthy volunteers into evacuated collection tubes containing the following anticoagulants: heparin, Na2EDTA, or K2EDTA. The concentrations of nonphosphorylated free thiamine (T), thiamine monophosphate (TMP), thiamine diphosphate (TDP), and thiamine triphosphate (TTP) were determined by the NH2-column HPLC method. The anticoagulant used had no effect on the concentrations obtained in whole blood and plasma of thiamine or any of the above thiamine compounds (P>0.05). RBCs were isolated by centrifugation and washed with isotonic saline, and the cell counts of the washed cells were adjusted to their whole blood values. In the washed RBCs with any anticoagulant, the concentrations of T, TMP, and TDP expressed either as nmol/L of whole blood or a ratio to hemoglobin were significantly lower (P<0.05) than those in whole blood.     

Lithium heparinised blood-collection tubes give falsely low albumin results with an automated bromcresol green method in haemodialysis patients

BACKGROUND: The aim of this study was to investigate the cause of markedly low albumin values determined by a bromcresol green (BCG) method in patients on haemodialysis. METHODS: Serum and heparinised plasma from haemodialysis patients and normal controls were collected. Albumin was measured using Beckman bromcresol purple (BCP) and Roche BCG methods on the Beckman Synchron LX20. RESULTS: The albumin in heparinised plasma determined by a BCG method was 33.3% lower than that of the BCP method in a haemodialysis patient. The albumin values determined by the BCP method were comparable to those measured by immunonephelometric analysis for this patient. Significantly lower albumin levels were also observed in lithium heparin plasma by a BCG method compared to the BCP method in both non-renal patients (31.2+/-3.8 vs. 34.1+/-4.1 g/L, p<0.001, n=30) and haemodialysis patients (28.6+/-3.5 vs. 32.8+/-3.7 g/L, p<0.001, n=30). This negative bias was directly correlated with heparin concentrations in the plasma. The BCP method did not show this dose-dependent bias. CONCLUSIONS: Lithium heparin plasma can cause falsely low albumin values by an automated BCG method and the suitability of lithium heparin blood tubes should be carefully assessed for haemodialysis patients. The BCP method is free of this bias.     

肝素锂抗凝血浆与血清样本中34项生化检测结果的偏倚评估

目的观察肝素锂对常规生化检测结果的影响,探讨肝素锂抗凝血浆能否用于生化检测以及能否用血清参考范围解释血浆检测结果。方法按美国临床实验室标准化委员会（NCCLS）的《用患者样本进行方法比对及偏倚评估：批准指南》（EP9-A方案）,随机抽取40例患者和健康体检者静脉血样本,分别注入红色真空采集管和肝素锂抗凝管中,于同一生化仪中对34项生化项目进行检测,并对结果进行统计学分析。结果34项测定指标中除脂蛋白（a）[Lp（8）]、前白蛋白（PA）、5’一核苷酸酶（5’-NT）、腺苷脱氨酶（ADA）外,其余各项目的相关系数（r）均≥0．975。34项指标中血浆与血清葡萄糖（Glu）、钾（K）、钠（Na）、氯（c1）、磷（P）的平均偏倚〉1／2美国临床医学检验部门修正法规（CLIA’88）允许误差。血浆Lp（a）、PA、5’NT、ADA检测结果与其血清检测结果相比,差异有统计学意义（P〈0．05）,平均偏倚均较大,分别为-11．9％、27．68％、-37．03％、29．31％;其余25项指标血浆测定值与血清测定值之间差异均〈1／2CLIA’88允许误差。结论大部分常规生化检验项目可用肝素锂抗凝血浆代替血清,但Glu、K、Na、Cl、P应建立血浆参考范围,其余项目可用血清参考范围解释血浆检测结果。Lp（a）、PA、5’NT、ADA项目不宜用肝素锂抗凝血浆作为样本进行测定。     

Effect of heparin and citrate on measured concentrations of various analytes in plasma

Frequently it is assumed that concentrations of biochemical analytes are similar for serum and plasma, without regard to the anticoagulant. Recently it has been hypothesized that use of certain anticoagulants results in an osmotic redistribution of fluid between blood cells and plasma, causing some dilution of the plasma. We sought to determine the effect of two commonly used anticoagulants, heparin and citrate, on the measured concentrations of 13 clinical-chemical analytes, including selected trace elements, vitamins, lipids, and proteins. The data demonstrate that hyperosmolar citrate causes a significant dilution of all indices measured. In contrast, heparin had no osmotic effect; concentrations of most of the analytes measured in the heparinized plasma were statistically no different from those measured in the corresponding serum. Therefore, anticoagulants must be chosen carefully, especially if concentrations in plasma and serum are to be compared.     

Avidin-biotin enzyme immunoassay of osteocalcin in serum or plasma.

We describe a competitive enzyme immunoassay, the ExtrAvidin-biotin system, for determining osteocalcin in human serum or plasma. Antibodies were raised against bovine osteocalcin. Binding of the antibodies to osteocalcin was calcium-dependent. Limit of detection is 0.07 nmol/L (0.4 microgram/L). The standard curve for method is linear between 0.3 and 17.6 nmol/L (1.9 and 100 micrograms/L). Interassay CV over the range 0.9 to 14.8 nmol/L (5.3 to 84 micrograms/L) is 7.5% to 11.7%. Analytical recovery is 105% +/- 5% (mean +/- SD). The measurement, which is adapted to microtiter plates, requires only 20 microL of serum and 5 h. The coefficient of correlation between the concentrations measured by this method and by a commercially available radioimmunoassay kit (CIS Biointernational) is 0.91. Osteocalcin can be measured in serum or heparinized plasma. Hemolysis (174 mumol/L hemoglobin) reduces osteocalcin concentration by 54%. High concentrations of triglycerides (7 mmol/L) give an overestimation of 63%. Serum concentrations of osteocalcin measured in 130 healthy subjects (ages 15-64 years) and 86 children (ages 4-14 years) were 1.4 +/- 0.8 and 4.0 +/- 1.5 nmol/L (8.1 +/- 4.6 and 22.5 +/- 8.6 micrograms/L), respectively (mean +/- SD).     

Heparin interference in whole blood sodium measurements in a pediatric setting

OBJECTIVES: In a pediatric setting, the incomplete filling of heparinized syringes is not an uncommon occurrence and has led to reports of falsely low hyponatremia in our institution. Little is known about heparin interference on sodium determination in whole blood, and our study aimed to investigate this interference due to excessive concentrations of heparin in pediatric specimens. DESIGN AND METHODS: Three different types of syringes were filled with various amounts of blood to mimic greater than normal concentrations of heparin. Specimens were analyzed on an ABL 725 blood gas analyzer, and corresponding plasma fractions were analyzed on a VITROS 950 chemistry system. In a separate study, paired patient samples consisting of a capillary tube and microtainer clot were similarly analyzed. RESULTS: The presence of lithium heparin at 100 units/mL in blood caused a significant negative bias of 2-3 mmol/L in sodium concentration with the ABL 725, but no significant bias occurred when the corresponding plasma fraction was analyzed on the VITROS 950. For syringes containing electrolyte-balanced heparin, a similar negative bias was observed for blood but was not significant. Capillary tubes contained high concentrations of heparin (>100 units/mL) even when completely filled. Sodium results from capillary samples averaged 3.4 mmol/L lower than the corresponding serum values. These effects were independent of the sodium concentration across a wide range. CONCLUSIONS: Small blood volumes collected with heparinized sampling devices in pediatric samples lead to excess heparin that may significantly affect sodium determinations and spur false reports of critical hyponatremia.     

Homologous radioimmunoassay of human osteocalcin.

Osteocalcin or bone gamma-glutamic acid-containing protein (GLA protein) was isolated from human bone and used to develop a homologous radioimmunoassay of human osteocalcin. The effect of age on serum osteocalcin was studied in 380 normal children and adolescents and 330 normal adults. The mean (+/- SD) values in adults were higher in men [25 +/- 5 micrograms/L (4.3 +/- 0.8 nmol/L)] than in premenopausal women [20 +/- 6 micrograms/L (3.4 +/- 1.0 nmol/L); P < 0.01], but both were lower than in postmenopausal women [29 +/- 2 micrograms/L (5.0 nmol/L)]. The highest concentrations were seen in girls [ages 10-12 years: 99 +/- 38 micrograms/L (17.0 nmol/L)] and boys [ages 14-16 years: 107 +/- 57 micrograms/L (18.4 nmol/L)]. These mean values were substantially higher than those previously reported for results of heterologous osteocalcin radioimmunoassays but the correlation (r = 0.87, n = 77, P < 0.001) between both sets of results was excellent. In patients with metabolic bone diseases characterized by high or low bone turnover, the increase or decrease in serum osteocalcin observed was as expected. This homologous radioimmunoassay of human osteocalcin thus reflects bone turnover but reports serum concentrations higher than previously suspected.     

不同抗凝剂对肝移植受者FK506血药浓度测定的影响及临床意义

目的探讨不同抗凝剂对肝移植受者他克莫司（FK506）血药浓度测定的影响及临床意义。方法采集肝移植受者静脉全血34份,使用乙二胺四乙酸二钾（EDTA-K2）、枸橼酸钠和肝素锂抗凝剂分别抗凝同一份血样本,在IMx型免疫分析仪上用微粒子酶免疫分析法（MEIA）测定FK506血药浓度。结果肝素锂组与EDTA组差异无统计学意义（P=0.660）,呈正相关（r=0.982 8）。枸橼酸钠组与EDTA组差异有统计学意义（P=0.000）,呈正相关（r=0.961 3）。枸橼酸钠组与肝素锂组差异有统计学意义（P=0.000）,呈正相关（r=0.939 8）。结论肝素锂组与EDTA组几乎无偏差,但是枸橼酸钠组分别与EDTA组和肝素锂组存在一定程度的负偏差。枸橼酸钠对MEIA测定FK506血药浓度有一定的影响,应优先考虑EDTA或肝素锂抗凝剂采集全血样本。     

不同抗凝剂对5种特定蛋白检测结果的影响

目的观察常见的4种血样采集管对C3、C4、IgA、IgG、IgM这5项生化项目检测结果的影响,探讨能否用抗凝血浆替代血清用于生化检测。方法对43名体检人员的静脉血管,连续用乙二胺四乙酸二钾(EDTA-K_2)抗凝管、肝素锂抗凝管、普通血清管、枸橼酸钠抗凝管各抽取一管血液,经混匀、离心分离后提取血清或血浆在仪器上同时用C3、C4、IgA、IgG、IgM试剂盒进行测定。结果在相同条件下,5个项目中肝素锂抗凝管与普通血清管比较差异无统计学意义(P0.05),枸橼酸钠抗凝管与用普通血清管的结果比较差异有统计学意义(P0.05),EDTA-K_2抗凝管与用普通血清管的结果比较,IgA、IgM、IgG差异无统计学意义(P0.05),C3、C4差异有统计学意义(P0.05)。结论 IgA、IgM、IgG生化检验项目可用肝素锂抗凝血浆和EDTAK2血浆代替血清,C3和C4生化检验项目可用肝素锂抗凝血浆代替血清,但C4应建立血浆参考区间。     

快速免疫荧光法检测血浆NT-proBNP的分析性能评价

目的 评价快速免疫荧光(RAMP)法检测血浆NT-proBNP的分析性能.方法 RAMP法测定264名健康体检者及78例心衰患者血浆NT-proBNP,参照CLSI方法 学评价方案,评价RAMP法的精密度、线性、稳定性及干扰因素等,并与瑞士罗氏公司Elecsys法检测方法 进行比对.结果 CV=20%时RAMP法功能灵敏度为48 ng/L,CV=10%时灵敏度为57 ng/L,线性范围18～8 000 ng/L.RAMP法NT-proBNP室温下稳定24 h,4℃稳定3 d,-20 ℃稳定20 d,反复冻融3次对检测结果 无影响.EDTA-K2和肝素抗凝血浆RAMP法测定结果 比对,YEDTA-K2=0.953 9X肝素+0.365 2,R2=0.982,P<0.01,n=40.两种类型的抗凝标本在两种方法 间的测量结果 差异无统计学意义(P＞0.05).轻度溶血(Hb=2 g/L)对RAMP法和Elecsys法测定结果 影响较小,偏差<5%,中、重度溶血(Hb=3～4 g/L)对结果 影响大,偏差＞15%.加入3种浓度三酰甘油时RMAP法测定值从390 ng/L降为82 ng/L,Elecsys法测定值从390 ng/L降为178 ng/L;当标本中胆红素含量为16～330 μmol/L,两种方法 测定值从7 777 ng/L降为7 741 ng/L,RAMP法抗乳糜和黄疸的干扰能力与Elecsys法相近.45份EDTA-K2抗凝血浆标本用2种方法 检测比对,Passing和Bablok回归方程显示:YRAMP=0.972 8XElecsys-0.035 2,R2=0.994,P＞0.05,n=45.78份肝素抗凝血浆标本用2种方法 检测比对,Passing和Bablok回归方程显示:YRAMP=0.983 2XElecsys-0.037 6,R2=0.991,P＞0.05,n=78.健康人血浆NT-proBNP水平随年龄递增,与性别相关,女性为105(60～120)ng/L,男性为59(44～91)ng/L,女性高于男性(Z=3.264,P<0.01).结论 RAMP快速免疫荧光法重复性,稳定性较好、线性范围宽,检测结果 与罗氏电化学发光法一致性较好.     

Analytical performance of time-resolved fluorometry-based Innotrac Aio! cardiac marker immunoassays

The results of an evaluation of the Innotrac Aio! cardiac markers are presented. This system is based on dry-chemistry, time-resolved fluorometry. All assay-specific reagents are dry-coated into assay-specific cups, and only the generic assay buffer is required. The levels of precision attained with pooled serum samples and control materials were acceptable for cTnI and CK-MB. Myoglobin assay showed higher CV, 5.6-9.5%. The linearity studies were performed in concentration ranges of 0.1-76 microg/L for cTnI, 0.7-450 microg/L for CK-MB and 0.6-1500 microg/L for myoglobin. The markers were found to be linear within the ranges tested. The correlation coefficient between the Aio! and AxSYM cTnI assays was 0.960, and the slope was 0.07. The correlation coefficients between the Aio! and AxSYM CK-MB and myoglobin assays were 0.995 and 0.971, respectively. They involved some differences in the measured concentrations (Aio! CK-MB was about 9% higher than AxSYM CK-MB, and Aio! myoglobin was 19% higher than AxSYM). Comparative studies with all the markers, using EDTA whole blood and lithium heparin plasma specimens and lithium heparin whole blood and plasma, yielded the following results: the slopes were close to 1.0 for all correlations, with the exception of that between CK-MB EDTA whole blood and lithium heparin (0.83). High correlation coefficients were obtained (> or = 0.97). The carryover results for all the cardiac markers were good, 0.0%, 0.0%, and 0.3% for cTnI, CK-MB, and myoglobin, respectively. The analytical detection limits were 0.01 microg/L for cTnI, 0.8 microg/L for CK-MB and 0.5 microg/L for myoglobin. The stability of the analytes in the lithium heparin samples at room temperature was also studied and was found to be decreased by from 10% (myoglobin and CK-MB) to 17% (cTnI) in 8 h. Innotrac Aio! provides a rapid and easy quantitative measurement of cardiac TnI, CK-MB, and myoglobin within < 18 min. This system is therefore suitable for use in emergency departments, coronary care units or central laboratory settings.     

Effects of N-deacetylation and N-desulfation of heparin on its anticoagulant activity and in vivo disposition

This investigation compares the anticoagulant activities and in vivo disposition characteristics of N-deacetylated heparin and N-desulfated heparin with those of standard heparin in an animal model. The N-deacetylated heparin retained 23% of the anticoagulant activity, 34% of the anti-Xa activity and 23% of the anti-IIa activity of standard heparin, whereas the N-desulfated heparin retained only 1.5% of the anticoagulant activity, 0.095% of the anti-Xa activity and 0.92% of the anti-IIa activity of the original heparin. After i.v. injections of 5 mg/kg of the modified heparins, both N-deacetylated and N-deacetylated heparin concentrations showed monoexponential declines with time. The elimination half-lives were similar, 11.7 +/- 3.8 and 13.5 +/- 5.2 min, respectively (N.S.). There were, however, significant differences in both total clearance (Cl) and apparent volume of distribution (Vd) for these heparins, both parameters being significantly larger for the N-deacetylated heparin (P = .0007). The Cl values were 4.15 +/- 1.11 and 0.58 +/- 0.26 ml/min/kg and the Vd values were 72.1 +/- 38.7 and 9.9 +/- 2.4 ml/kg for the N-deacetylated and N-desulfated heparins, respectively. We have reported previously that after a similar dose of standard heparin the elimination half-life was 69.0 +/- 13.1 min, Cl was 0.64 +/- 0.16 ml/min/kg and Vd was 62.6 +/- 16.7 ml/kg. These studies have thus demonstrated that selective N-deacetylation and N-desulfation of the glucosamine residues of heparin affect markedly both its anticoagulant activity and in vivo disposition characteristics. Although important for full anticoagulant activity of heparin, the N-acetyl groups are apparently not essential.(ABSTRACT TRUNCATED AT 250 WORDS)     

不同标本类型间髓过氧化物酶水平的检测分析

目的探讨不同标本类型间髓过氧化物酶(MPO)检测结果的差异性、抗凝剂的选择及检测结果的比对。方法同时采集165例健康体检人群含乙二胺四乙酸二钾(EDTA-K2)、肝素钠两种抗凝剂的血浆标本及不含抗凝剂的普通生化管的血清标本,分别检测3种标本类型中MPO水平,并对各组检测结果进行统计学分析。结果同一例体检者不同抗凝剂的血浆标本间及与不含抗凝剂的血清标本间MPO检测结果差异有统计学意义(P0.05)。结论不同标本类型对血液标本中MPO水平检测结果差异较大,建议各个实验室检测时根据不同抗凝剂制订相应的参考区间;由于EDTA-K2抗凝血浆不受体外白细胞中MPO释放的影响,推荐采用EDTA-K2抗凝血作为检测MPO水平的首选。     

Influence of pre-analytical and analytical factors on soluble CD40L measurements

The soluble form of CD40L (CD40 ligand), a pro-atherogenic mediator, has emerged as a diagnostic and prognostic marker for cardiovascular events. However, as platelets can shed CD40L upon activation, accurate measurement has proved challenging. The present study addresses the controversy regarding the appropriate specimen and preparation for laboratory evaluation of blood sCD40L (soluble CD40L). Serum and plasma (collected in EDTA, citrate or heparin) were collected from healthy volunteers (n=20), and sCD40L was analysed by ELISA immediately or after one to three freeze-thaw cycles and at different centrifugation speeds. Urine sCD40L levels were measured in subjects with low- and high-plasma sCD40L levels. Serum sCD40L levels (5.45+/-4.55 ng/ml; P<0.001) were higher than in citrate, EDTA or heparin plasma (1.03+/-1.07, 1.43+/-1.03 or 1.80+/-1.25 ng/ml respectively), with no significant differences between plasma preparations. Increasing g values (200-13000 g), which gradually deplete plasma of platelets, yielded lower sCD40L levels. Repeated freeze-thaw cycles significantly (P<0.05) increased sCD40L concentrations in platelet-rich, but not platelet-depleted, plasma (up to 2.4-fold). Bilirubin and haemoglobin interfered positively, and triacylglycerols (triglycerides) and cholesterol quenched CD40L signalling. No sCD40L was detected in urine samples. In conclusion, serum yields higher sCD40L concentrations than plasma; accurate measurements of sCD40L require exclusion of platelets and avoiding their post-hoc activation. Samples with high concentrations of bilirubin, haemoglobin and/or triacylglycerols should be excluded, as these substances interfere with the assay.     

不同血液样本在生化项目检测中的结果比较

目的比较血清样本、不同抗凝血浆在常规生化项目检测中的结果差异。方法对50例体检者的5种不同血液样本(血清、肝素锂血浆、枸橼酸钠血浆、乙二胺四乙酸二钾(EDTA-K2)血浆、HMF血浆)在相同测量条件下测定15项生化指标。结果与血清组比较:肝素锂血浆组碱性磷酸酶(ALP)、清蛋白(ALB)、总胆固醇(TC)、三酰甘油(TG)、低密度脂蛋白胆固醇(HDL-C)的检测结果差异有统计学意义(P<0.05),天门冬氨酸氨基转移酶(AST)的检测结果差异有统计学意义(P<0.01);EDTA-K2血浆组除高密度脂蛋白胆固醇(HDL-C)、肌酐(Cr),5-羟甲基糖酫(HMF)血浆组除LDH-C的检测结果差异无统计学意义(P>0.05),其余各抗凝血浆组生化项目的检测结果均与血清组差异有统计学意义(P<0.05)。结论不同的血液标本对常规生化项目的检测几乎都具有显著性的差异,应根据WHO建议选用适宜的标本类型进行分别检测。     

Choline in whole blood and plasma: sample preparation and stability

BACKGROUND: Choline is critical for a variety of biological functions and has been investigated as a biomarker for various pathological conditions including acute coronary syndrome. METHODS: A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was used to quantify choline in whole blood and plasma in freshly collected samples prepared with ultrafiltration or protein precipitation. We investigated the effects of preanalytical variables including types of anticoagulants and storage temperature and time. RESULTS: We observed no significant differences in whole-blood choline concentration in EDTA-anticoagulated vs heparin-anticoagulated samples: mean (SD) difference 0.9% (3.2%), P = 0.80. For plasma, choline concentrations with heparin in 5 of 12 volunteers were >10% higher than with EDTA, P = 0.01. One freeze-thaw cycle led to significant mean (SD) increases in choline concentrations in heparin whole blood, 19.3% (11.4%), P <0.01, and the effect was not significant for other sample types studied (P >0.33). For freshly collected samples stored at ambient temperature, choline concentrations in all types of samples increased with storage time. For EDTA whole blood, EDTA plasma, and heparin plasma, the choline concentration increased for the first 60 min and then stabilized. For heparin whole blood, the choline concentration continued to increase linearly with storage time for >4 h, at which time the choline concentrations were increased by approximately 50%. CONCLUSIONS: Sample collection, storage, and sample preparation procedures are critical for clinical measurements of choline in whole blood and plasma.     

肝素锂对比浊法检测微量总蛋白的干扰分析

目的证实肝素锂对比浊法检测微量总蛋白的干扰效应,并对其进行相关方法性能评价。方法分别配对检测8份不同浓度微量总蛋白尿液干扰标本,筛查判断肝素锂是否是试验的干扰物;浓度0.172、0.427g/L微量蛋白质标本中分别加入不同量的肝素锂(干扰物试验系列样品,肝素锂浓度分别为0.000、0.025、0.030、0.035、0.040、0.045、0.050mg/L),重复检测4次,进行干扰物剂量效应试验。结果干扰标本检测结果显示,8份含肝素锂与不含肝素锂的配对标本中最大偏倚为159.37%,最小偏倚为11.37%,2组间结果差异有统计学意义(t=17.24,P0.05);浓度为0.025mg/L肝素锂对0.172g/L微量蛋白质标本干扰效果的95%置信区间为0.034~0.062;0.030mg/L肝素锂对0.427g/L干扰效果的95%置信区间为0.043~0.053;肝素锂浓度分别为0.025mg/mL和0.050mg/mL时,0.172g/L微量蛋白质标本的结果偏倚分别为27.33%、58.14%;肝素锂浓度分别为0.030mg/mL和0.050mg/mL时,0.427g/L微量蛋白质标本的结果偏倚分别为11.24%、18.74%;同系列浓度的肝素锂对0.172g/L和0.427g/L微量蛋白质标本的干扰物剂量呈线性相关,其线性方程分别为Y=1.974 X-0.001 03,Y=1.599 X-0.000 5。结论肝素锂是比浊法检测微量蛋白质的外源性干扰物,它对微量蛋白质检测结果为正干扰,特别对低水平微量蛋白质检测的干扰效果更明显,且随着肝素锂浓度升高,干扰效果越强。     

Results from a multicenter evaluation of the 4th generation Elecsys Troponin T assay

BACKGROUND AND OBJECTIVE: Discrepancies between serum and heparin plasma samples have been described for many commercial troponin assays including the cardiac troponin T (cTnT) assay. Using the current 3rd generation Elecsys Troponin T immunoassay, heparin plasma cannot be recommended for the determination of cTnT due to systematic lower test results caused by a direct interference of the immunoassay by heparin. The purpose of the multicenter study was to evaluate the analytical performance of an improved 4th generation Elecsys Troponin T immunoassay with a special focus on the comparability of cTnT results determined in heparin plasma and serum. METHODS AND RESULTS: The multicenter evaluation was performed in 10 clinical laboratories according to a standardized protocol (Roche Diagnostics, Penzberg, Germany, Study No. B05P008). The Elecsys Troponin T immunoassay was performed on the Modular Analytics E170 and Elecsys 2010 systems. Intraassay imprecision (n = 21) and total imprecision (2 runs/d, 10 days, triplicate measurements) were evaluated using 2 commercial controls (Roche Diagnostics) and 6 different serum pools (cTnT: 0.0140 - 4.102 microg/L). Intraassay CVs ranged from 0.73 to 3.22%. Total imprecision CVs ranged from 3.61 to 35.45% (cTnT < 0.1 microg/L) and 1.82 to 9.09% (cTnT > 0.1 microg/L), respectively. The cut-off for myocardial necrosis was determined to be 0.03 microg/L using the 10% total imprecision CV criteria. Linearity was assessed by serial dilutions of 6 different serum samples using cTnT negative serum pools. Linearity was proven up to 21.3 microg/L (recoveries: 90% - 110%). Regression data of all comparison studies were calculated according to the method of Passing and Bablok. The method comparison between the 4th generation and the commercially available cTnT immunoassay showed highly similar results across the whole measuring range (0.01 - 25.0 microg/L): y = 1.024x -0.001, r = 0.998; n = 988. Using the commercially available cTnT reagent, the serum to heparin plasma comparison yielded a systematic bias to approximately 8% lower cTnT results in heparin plasma. However, suitable comparability was obtained using the 4th generation Elecsys cTnT assay. The regression analysis (serum vs. heparin plasma) across the studied measuring range (cTnT: 0.01 - 14 microg/L) yielded the following equation: y = 0.975x + 0.001; r = 0.986; n = 403. However, rare individual serum to matched heparin plasma samples still yielded poor comparability (deviation > 20%) using the 4th generation Elecsys Troponin T immunoassay. CONCLUSION: Our data confirm an excellent analytical performance of the improved troponin T immunoassay. Most importantly, no systematic bias between cTnT results determined in serum and heparin plasma was observed from data obtained in 7 evaluation sites. The performance of the 4th generation Elecsys Troponin T assay is therefore comparable to other commercially available troponin immunoassays. Further studies are necessary to investigate the cause of poor comparability of cTnT results in rare individual serum to matched heparin plasma samples.     

使用添加剂处理标本对离子选择电极法测定血锂浓度的影响

目的　探讨使用肝素钠抗凝剂、促凝剂、分离胶等添加剂处理的标本是否适合锂盐(Li+ )浓度的监测。方法　选择临床服用碳酸锂治疗达稳态的住院患者,使用真空采血系统分别采集普通管血液标本和分别含有肝素钠抗凝剂、促凝剂、分离胶等添加剂的标本,在IMS 972电解质分析仪上测定Li+浓度,比较结果的差异。结果　(1)不同方式处理的标本间Li+浓度差异有显著性(P<0. 001),其中普通血清、肝素钠抗凝血浆、促凝剂处理的血清之间Li+浓度差异均无显著性(P>0. 05),分离胶处理的标本与普通血清、促凝剂和肝素钠处理的标本之间Li+浓度差异均有显著性(P<0. 001); (2)肝素钠抗凝剂和促凝剂处理的标本与普通血清Li+浓度之间呈高度线性相关(r=0. 988~0. 993, P<0. 001),分离胶处理的标本与普通血清、肝素钠抗凝剂、促凝剂处理标本的Li+浓度线性相关均无显著性(r=0. 203~0. 288,P>0. 05); (3)肝素钠抗凝剂、促凝剂、分离胶等添加剂处理标本和普通血液标本,不分离血凝块室温放置8h,Li+浓度较放置前增高(P<0. 05~0. 001)。结论　促凝剂和肝素处理标本适合用于锂盐的快速测定,而分离胶处理的标本不适合用于离子选择电极法测定Li+浓度,也不适于储存和标本运输;使用肝素钠抗凝剂和促凝剂处理的标本,不能及时测定时应分离血浆或血