Influence of short-term venous stasis on clinical chemistry testing.

Control and standardization of preanalytical variability is a critical factor for achieving accuracy and precision in laboratory testing. Although venous stasis from tourniquet placement during venepuncture should be minimized, as it has been claimed to account for spurious and significant variations for several analytes in plasma, there is controversy surrounding its real impact on laboratory testing. The aim of the present study was the investigation of the influence of short-term venous stasis on routine biochemical testing, by measuring the plasma concentration of 12 common analytes, including proteins, protein-bound substances, enzymes and electrolytes, in plasma specimens collected either without venous stasis or following the application of standardized external pressure of 60 mm Hg using a sphygmomanometer for 1 and 3 min. Although the overall correlation between measures was acceptable, the pattern of change was mostly dependent on the length of stasis, size and protein-binding characteristics of the analytes, achieving clinical significance for albumin, calcium and potassium after 1-min stasis, and alanine aminotransferase, albumin, calcium, chloride, total cholesterol, glucose and potassium after 3-min stasis. Statistically significant differences could be observed in seven (alanine aminotransferase, albumin, calcium, total cholesterol, creatine kinase, iron and potassium) and ten (alanine aminotransferase, albumin, calcium, chloride, total cholesterol, creatine kinase, creatinine, glucose, iron and potassium) out of the 12 analytes tested, after 1- and 3-min venous stasis, respectively. The most clinically significant changes from standard venepuncture, when compared to the current analytical quality specifications for desirable bias, occurred for potassium (1-min stasis, -2.8%; 3-min stasis, -4.8%, both p<0.001), calcium (1-min stasis, +1.6%, p<0.05; 3-min stasis, +3.6%, p<0.001) and albumin (1-min stasis, +3.5%; 3-min stasis, +8.6%, both p<0.001). As most of these effects are dependent on the stasis time during venepuncture and biochemical or physiological characteristics of the analyte, these variations could likely be anticipated, allowing the most appropriate preventive measures to be adopted.     

Influence of the needle bore size used for collecting venous blood samples on routine clinical chemistry testing.

BACKGROUND: Despite remarkable advances in technology and laboratory automation, results of laboratory testing still suffer from a high degree of preanalytical variability. Although there is no definitive evidence, the use of small-gauge needles for venipuncture is usually discouraged to reduce the chance of producing unsuitable specimens. METHODS: The purpose of this investigation was to assess the influence of the needle size used to collect venous blood on the measurement of 14 common analytes, including free hemoglobin, the most representative enzymes, protein-bound substances and electrolytes. Results for venous blood samples collected from 20 fasting voluntary physicians using either a 23- (0.60 mmx19 mm) or 25-gauge-needle (0.50 mmx19 mm) butterfly devices with polyvinyl chloride tubing (1.40 mmx300 mm) were compared with reference specimens collected using a 21-gauge-needle (0.80 mmx19 mm) butterfly device with polyvinyl chloride tubing (1.40 mmx300 mm). RESULTS: All means for paired samples collected using the smaller needles did not differ significantly from the reference specimen by paired Student's t-test analysis. Passing-Bablok regression analysis and Pearson's or Spearman (creatine kinase, aspartate aminotransferase, alanine aminotransferase and chloride) correlation were acceptable for most of the analyses, although a lower correlation coefficient was observed for electrolytes. In addition, when expressed as a percentage of the mean for paired samples, the s(y,x) value exceeded the desirable bias for free hemoglobin, glucose, lactate dehydrogenase, aspartate aminotransferase, sodium, chloride, calcium and magnesium (in samples collected using both 23 G and 25 G needles) and potassium (in samples collected using a 25 G needle). Although Bland-Altman plot analysis and +/-1.96 SD agreement intervals for the set of differences between values was acceptable overall, the bias was rather broad for free hemoglobin and several critical electrolytes (calcium, chloride, potassium, sodium), exceeding the respective limits for desirable bias. CONCLUSIONS: The results of our investigation indicate that 23 G needles, if handled correctly, will not introduce any statistically or clinically significant error to the measurement results compared to a 21 G needle. For the 25 G needle, we observed increased variability for potassium compared to a 23 G needle. Small-bore needles of 25 G or less cannot be universally recommended when collecting venous blood for clinical chemistry testing and should be reserved for selected circumstances, such as in patients with problematical venous accesses and newborns. In such cases, however, the bias introduced by the use of smaller needles should always be taken into consideration when interpreting test results.     

上海市常规化学项目检验结果互认基础探讨

目的分析2010至2011年上海市医院实验室常规化学项目飞行检查结果,为上海市医疗机构检验结果互认工作提供依据。方法收集2010至2011年上海市二级甲等以上医院实验室参加由上海市临床检验中心组织的2次飞行检查常规化学项目结果,计算实验室的合格率,并分别比较20个常规化学项目的全部参加实验室、三级医院、二级甲等医院和通过认可实验室检测结果间的离散度,用基于允许误差和生物学变异的分析变异质量标准评价每个项目的达标情况。结果上海二级甲等以上医院实验室间离散度分析,电解质[钾(K)、钠(Na)、氯(Cl)]3项和尿酸(UA)<3.0%,且Na≤1.6%;白蛋白(Alb)、钙(Ca)、肌酐(Cr)、总胆固醇(TC)、葡萄糖(Glu)、总蛋白(TP)均<5.0%;磷(P)、甘油三酯(TG)、尿素(Urea)和丙氨酸氨基转移酶(ALT)≤7.9%;天门冬氨酸氨基转移酶(AST)、γ-谷氨酰基转移酶(GGT)、乳酸脱氢酶(LDH)、肌酸激酶(CK)和总胆红素(TBil)离散度≤11.4%;高密度脂蛋白胆固醇(HDL-C)最大,术17.9%。认可实验室的Alb、ALT、AST、Ca、TC、TG、TP和CK检测质量相对优于其他组;全部医院、二级甲等医院、三级医院和认可实验室组间的均值基本无差异。ALT、CK和TG是20项常规化学检测中可达到较高质量标准的项目;其次为AST、K、TBil、UA和Urea;然后为Alb、Ca、Cr、Glu、P、TC和TP;Na、Cl、HDL-C、LDH和GGT为达到最低质量标准的项目。结论通过开展实验室全面质量管理,建立检测项目参考体系,开展中国人群基础数据研究,加强质控管理,以此为基础,逐步达到检测结果的互认,为临床提供可靠的诊疗依据。     

Self testing, an emerging component of clinical chemistry

Self testing as a phase of health delivery has been utilized for approximately 70 years, but within the last two decades there has been an increasing interest in and use of self testing. The practice of self testing has a sound basis, which involves medical relevancy, cost containment, and convenience. It is reasonable to anticipate that self testing will increase in the future as medical needs and available procedures are established. The clinical chemist, the physician, and the industrial producer of test systems all have important roles in self testing. The clinical chemist, whether in a hospital laboratory or in an industrial setting, has the responsibility to create new self-testing procedures that represent expansion and improvement over those currently available. The clinical chemist also has a critical role in the evaluation of new self-testing procedures and in validating their capability of providing high-quality information. The provision of quality-assurance programs and proficiency programs for the user can most effectively be carried out by clinical chemists. The clinical chemist can also play an important role as a consultant, teacher/educator, and trouble shooter in recognizing and helping solve problems that may appear in various areas of self testing. The classic role of the physician has been to diagnose disorders of the patients and provide therapy for effective care. The role of the physician in self testing is quite comparable to his usual role, since the ultimate diagnosis of disease will be carried out by the physician and he will continue to be the source for definition of therapy. A major portion of self testing will be carried out with the recommendation of a physician, and he will maintain a role in the interpretation of results. The physician needs to be familiar with self-testing practices and procedures and be prepared to provide interpretation of self-testing results. Industry supplies an increasing proportion of reagent systems and instruments for the clinical laboratory. The supplying of reagent systems and small instruments for self testing is almost completely a role of industry. The creation and funding of new products for self testing will be provided by industry to a large extent. A critical function of industry is to provide high-quality products and efficient customer service to the self-testing component of health delivery. We have each played a role in self testing over a period of approximately 40 years. During this period self testing has become an important phase of clinical laboratory practice.(ABSTRACT TRUNCATED AT 400 WORDS)     

The diagnostic value of anti-neutrophil cytoplasmic antibody testing in a routine clinical setting.

Anti-neutrophil cytoplasmic antibody (ANCA) tests are a routine clinical assay in most UK hospitals. We examined the role of routine ANCA testing in achieving a diagnosis of systemic vasculitis in a routine clinical setting. From April 1996 to March 2000, 2734 samples from five hospital departments were tested for ANCA by indirect immunofluorescence (IIF) at a single laboratory. After April 1999, enzyme-linked immunosorbent assays (ELISAs) were performed on all IIF-positive samples. Clinical diagnosis was determined for all patients with a positive IIF ANCA, and a sample of the ANCA-negative patients. Some 2-18% of patients with suspected ANCA-associated systemic vasculitis (AASV) had positive IIF ANCA. The AASV diagnosis was confirmed in 0-56% of these cases. Analysis by department suggested that 88-100% of patients with a positive IIF ANCA did not have AASV, except in the Rheumatology department. The positive predictive value (PPV) of IIF ANCA for AASV was 59% and the negative predictive value (NPV) was 84%. Of the patients with proven AASV, 41% did not have ANCA on IIF. Combined ANCA testing by IIF/ELISA had a higher sensitivity and PPV but lower specificity than IIF alone for AASV. For the combined IIF/ELISA test, only the Rheumatology department had a sensitivity or PPV >0% for AASV. The PPV of ANCA by IIF/ELISA for AASV was 79% and the NPV was 63%. The ANCA test is being widely applied with very poor return. Guidelines for more effective usage are proposed.     

标本溶血对常规生化检验结果的影响

目的了解临床标本溶血对丙氨酸氨基转移酶(ALT)、天门冬氨酸氨基转移酶(AST)、总胆固醇(TC)等11项常规生化检验结果的影响,探讨影响因素并在此基础上提出相应对策。方法抽取100例体检者空腹血液标本5mL,分别置于2支试管中,每支2.5mL,其中1支试管中的标本采用人工方法使其溶血,检测正常标本和溶血标本血清中ALT、AST、三酰甘油(TG)、尿素(UREA)、肌酐(Cr)、葡萄糖(GLU)、尿酸(UA)等11项临床常规生化检验指标的含量并进行比较。结果溶血标本血清ALT、AST、总蛋白、清蛋白测定结果明显高于正常标本血清,差异有统计学意义(P<0.05),溶血后总胆红素、Cr、TC、TG及GLU较溶血前均有明显降低,差异有统计学意义(P<0.05),溶血对UREA、UA测定结果影响较小。结论标本溶血对一些常规生化检验项目有明显的干扰作用,临床检验工作中应采取一切可能的措施避免标本溶血的发生。     

Automation of routine chemistry analysis

A variety of chemistry analyzers exist for performing routine analysis, including sample-based and random access instruments with a wide range of throughput capabilities. Representative analyzers based on dry and liquid reagent technology are discussed.     

常规化学项目总误差和不确定度比较研究

目的分别利用总误差(TE)和不确定度的统计方法评价常规化学项目的性能。方法使用上海市临床检验中心室内质量控制软件统计2012年1至9月本实验室常规化学项目室内质量控制累积均值(x珋)、累积标准差(s)、累积变异系数(CV),利用美国病理学家协会(CAP)全球室间质评回报数据[共2次(C3-A、C3-B)]计算常规化学项目检测结果与靶值的相对偏倚(bias%)和相对平均偏倚(bias%),结合室内质量控制累积CV计算TE。使用CAP室间常规化学回报数据和室内质量控制累积CV,采用Nordtest方法计算每个项目的不确定度。结果 3个质量控制水平的葡萄糖(Glu)、肌酐(Cr)、尿素氮(BUN)、总蛋白(TP)、白蛋白(Alb)、尿酸(UA)、总胆红素(TBil)、丙氨酸氨基转移酶(ALT)、胆固醇(Chol)、甘油三酯(TG)、天门冬氨酸氨基转移酶(AST)、碱性磷酸酶(ALP)、乳酸脱氢酶(LDH)、高密度脂蛋白胆固醇(HDL-C)的最大TE分别为5.40%、6.01%、9.37%、3.00%、6.52%、3.77%、26.79%、5.34%、4.03%、9.42%、9.25%、8.37%、6.19%、9.54%;这些项目的扩展不确定度分别为6.37%、6.50%、10.64%、3.23%、13.01%、4.84%、31.07%、6.00%、4.37%、13.27%、14.12%、10.07%、6.95%、14.08%。除Alb的不确定度超过美国临床实验室改进修正案(CLIA’88)和生物学变异所允许的范围外,其他项目均处于范围之内。结论 TE和不确定度之间具有较好的一致性,可作为实验室检测质量分析和改进的重要依据。     

全国常规化学检验项目参考区间现状调查分析

目的 描述常规化学检验项目参考区间上下限回报结果以及来源,比较北京地区的参加单位常规化学与干化学各项目参考区间的差异.方法 把卫生部临床检验中心2010年全国常规化学和干化学第3次室间质量评价回报结果中各项目的参考区间信息纳入研究.剔除所有妇幼保健院、儿童医院和公司的结果,以及所有异常值和错误数据(如下限高于上限、上下限相同等),并对全国参评单位常规化学和干化学参考区间的基本情况以及来源(如果存在性别间差异则报告成年男性水平)进行描述.使用SPSS 13.0分析北京市参评单位常规化学与干化学各项目参考区间的差异.结果 参考区间来源中所占比例最高的3项包括临床检验操作规程483家(47.6％)、试剂厂家说明书295家(29.1％)以及实验室自己确定124家(12.2％).在北京地区参加单位常规化学和干化学参考区间的比较中,有6项下限及上限差异均有统计学意义,有4项出现单侧界限差异有统计学意义.结论 目前各医疗机构常规化学项目参考区间差异明显,来源不统一,各医疗单位常规化学与干化学项目参考区间只有少数项目存在统计学显著性差异,但是否具有临床实际意义有待进一步研究.为了实现医疗机构检验结果互认,必须在标准化基础上,在一定区域内共享相同的参考区间.     

标本溶血对生化检验结果的影响

目的：探讨标本溶血对生化检验结果的影响。方法：用日立7020全自动生化分析仪检测20份正常人血液标本溶血前和溶血后的谷丙转转氨酶（ALT）、谷草转氨酶（AST）、碱性磷酸酶（ALP）、γ－谷氨酰转肽酶（γ－GT），总蛋白（TP）、白蛋白（ALB）、总胆红素（TBIL）、直接胆红素（DBIL）、尿素氮（BUN）、肌肝（CRE）、尿酸（UA）、葡萄糖（Glu）、胆固醇（CHO）、甘油三酯（TG）、载脂蛋白－A（APo-A）、载脂蛋白－B（APo-B)、高密度胆蛋白（DHL－C）、钙（Ca)、乳酸脱氢酶（LDH）的值，并进行了比较和统计分析。结果：ATL、AST、ALP、γ－GT、TBIL、DBIL、CRE、GLu,Apo-B、LDH的值在溶血前后有非常显著性差别（P＜0．001），APo-A的值在溶血前后有显著性差别（P＜0．05），其中，ALT、AS、TBIL、DBIL、LDH的值溶血后比溶血测得的值高，ALP、γ－GT、CRE、GLu、APo-A,APo-B的值溶血后比溶血前测得的值低，而TP、ALB、BUN、DHL－C、CHO、TG、Ca、UA的值在溶血前后则无显著性差别（P＞0．05）。结论：溶血对较多的生化检验项目有明显的干扰影响，其机制有多种原因，应尽量避免或减少标本的溶血，使检验结果更准确可靠。     

标本溶血对电化学发光免疫法结果的影响

目的探讨标本不同程度溶血对电化学发光免疫法(ECLIA)测定结果的影响。方法将血液标本人为干预成不同程度的溶血标本,使用ECLIA检测各组标本中的甲状腺功能、肿瘤标志物、内分泌激素等共28项指标的浓度并做分析。结果标本溶血可使胰岛素(INS)浓度降低,使叶酸(FA)、神经元特异性烯醇化酶(NSE)浓度升高,重度溶血有使铁蛋白测定结果偏高的趋势,但差异无统计学意义,其余指标测定结果不受溶血的影响。结论除某些项目外大部分溶血标本的ECLIA测定结果没有受到影响。测定INS、FA、NSE时应绝对避免使用溶血标本,以确保结果准确。     

脑脊液和浆膜腔积液常用临床化学分析项目循证评价进展

临床实验室查明各种体液[脑脊液(CSF)、胸腔积液、腹腔积液等]的异常和积液病因,对于明确诊断和合理治疗相关疾病(如感染性疾病、原发性或转移性肿瘤)至关重要,准确解释体液实验室检查结果区间取决于合格的标本采集、及