External Quality Assessment Schemes: need for recognised requirements.

Programs for Accreditation of clinical laboratories consider participation in External Quality Assessment Schemes (EQAS) a key element in the evaluation of testing procedures and improving them. One of the main functions of EQAS is to assess whether laboratories perform tests competently. It is therefore of utmost importance for laboratories to participate in EQAS that are in line with formally recognised requirements. Specific proposals have been made on how to design and execute EQAS by International Working Groups, but there seems to be no consensus on the best strategies to use and quality specifications to set out. The Clinical Pathology Accreditation (CPA) Program for EQA Scheme Accreditation (CPA-EQA) is the only program in Europe to provide a formal recognition of the quality of EQAS activities. The present paper reports on the experience of the Centre of Biomedical Research which is following an accreditation process for their own schemes in line with the CPA-EQA program and a proposal to set requirements that Italian schemes must follow to be recognised as valid and effective.     

A new quality control model using performance goals based on biological variation in External Quality Assurance Schemes.

A new quality control model using performance goals based on biological variation in External Quality Assurance Schemes (EQAS) is described. The proposed model aims to use assay (analytical) CV(A), bias and total error available from participation in EQAS to describe assay performance using minimum, desirable and optimum quality specifications based on biological variation. The model provides further analysis of EQAS data and should be useful in better management of laboratory quality control, as it provides further information that can facilitate trouble-shooting. Additionally, it can help in evaluating the performance of current and proposed new laboratory methods by applying a unifying system if different EQAS are used to cover a range of analytes.     

Performance of proficiency survey samples in two immunoradiometric assays of human growth hormone and comparison with patients' samples.

The immunoradiometric assay (IRMA) used in our laboratory for the measurement of growth hormone (hGH; somatotropin) performed badly in the national proficiency survey program, the U.K. External Quality Assessment Scheme (EQAS). We compared our assay with another IRMA, which gave similar results for patients' samples and performed adequately in EQAS. The samples from EQAS are collected from patients with polycythemia and fall into two categories: those containing endogenous hGH and those supplemented with pituitary-derived hGH. Analysis of the two groups separately showed that the differences between the two IRMAS were in the measurement of the endogenous hormone. The reason for this appears to be a matrix effect related to the fact that the EQAS serum samples are collected from polycythemic patients.     

A modified statistical approach for the detection of outlying values in external quality control: comparison with other techniques

Laboratory results submitted to External Quality Assessment Schemes (EQAS) are evaluated against the arithmetic mean (m) and standard deviation (SD) of the result from other participants assuming a normal distribution of individual results. The sample statistics m and SD can only be reliable estimates of the theoretical mean (mu) and standard deviation (sigma), if they are not distorted by outlying values. Outliers are commonly detected by defining a confidence interval m +/- k SD, typically with k-values fixed at 3.0 or 3.2. The objective of our study was to prove the deficiency of the use of these fixed limits in large-scale EQAS, because it results in an unacceptable increase of outlier rate and hence in a serious distortion of the estimate of sigma. We have proposed a modified approach using a variable k-value which is dependent upon sample size and keeping the significance level constant at 5%. The influence of different decision limits on the number of outliers and on the sample statistics m and SD was compared using data from the Belgian National EQAS obtained in 6 consecutive surveys.     

Guidelines for blood smear preparation and staining procedure for setting up an external quality assessment scheme for blood smear interpretation. Part I: Control material.

Blood smear analysis is a well known technique in medical laboratories. Clinical relevance of this analysis and its interpretation are very important. Consequently, monitoring of laboratory performance by an external quality assessment scheme is strongly recommended. Most starting external quality organizers set up a scheme for clinical chemistry. Due to a lack of guidance documents, many organizers are reluctant to offer a hematology scheme. This article aims to be a very practical guidance document for external quality assessment organizers for the set up of blood smear schemes.     

Factors associated with the quality of laboratory performance in the United Kingdom external quality assessment scheme for serum growth hormone

A search was made for associations between poor performance in the UK External Quality Assessment Scheme (EQAS) for serum growth hormone (GH), and a range of factors including assay method, laboratory workload and staffing, and Internal Quality Control (IQC) procedures. On the basis of the factors identified as being associated with poor performance we recommend the following. 1. Laboratories using RIA for GH should routinely analyse samples at two dilutions and report a mean result. 2. The use of 125I-GH which is 5 or more weeks old should be avoided. Tracer should also be chromatographed to remove aggregate before use. 3. Laboratories using RIA should avoid using a standard curve which covers too wide a range concentration; a curve midpoint (ie GH concentration to reduce the zero standard binding by 50%) of about 8 mU/l or less is probably acceptable. 4. It should be noted that high workloads present a risk of some loss in quality of responsible for checking IQC data. 6. Laboratories which do not have the resources to maintain fully their own RIA as outlined above should carefully consider use of an unbiased, precise IRMA. The UK EQAS has identified two assays (Boots-Celltech Sucrosep, NETRIA) that appear to meet these criteria [2]. The above observations may also be relevant to immunoassays for other peptide hormones.     

Between-lot variation in external quality assessment of glucose: clinical importance and effect on participant performance evaluation

BACKGROUND: External quality assessment schemes (EQAS) are conducted to evaluate user performance (participant assessment) and to assess different methods and instruments (method assessment). The quality of control materials is crucial to achieving these goals. Inconsistencies in between-lot variations detected by use of different control and sample materials may affect EQAS outcomes. METHODS: For the Accu-Chek Sensor, Precision Xtra, Ascensia Elite, and HemoCue 201 glucometers, 3 different lots of glucose strips were used with each instrument. Method assessment results from analysis of capillary blood and 3 control materials were used to calculate between-lot differences. A simulation study was performed to evaluate the effect of between-lot variation on participant assessment results. RESULTS: With the Precision Xtra, the results obtained with EQA control material mirrored those obtained with capillary blood, but for the other instruments, we found between-lot differences of as much as 1.3 mmol/L, which were substantially greater than those found with capillary blood and of clinical importance at decision limits. The simulation study showed an effect on participant assessment results related to the target values, with the percentage of poor results decreasing (38%, 10%, and 4%) with the use of common, method-specific, and lot-specific target values, respectively. CONCLUSIONS: Between-lot variation may influence participant EQA results for participant and method assessments. The clinical relevance of between-lot variation discovered in EQAS using noncommutable control materials should be examined by use of native blood samples.     

Evaluation of external quality assessment results for HIV testing laboratories in Korea using current analytical methods

BackgroundThis report presents HIV External Quality Assessment (EQAS) results by the KCDC from the 17 HIV testing laboratories that also performed HIV-1 western blot testing of the 585 laboratories.MethodThe HIV EQAS panel consisted of 10 undiluted plasma samples from donors who were 3 positive, four indeterminate and 3 negative for HIV antibody. The results were analyzed by traditional methods (mean ± 2 SD), robust statistics (median), and Youden plots (99% coverage).ResultsThe sensitivities for the HIV antigen and antibody ELISAs were 94.1% and 98.3%, respectively, with the inconsistent 1.7% caused by indeterminate, weakly positive samples. The specificities of HIV antigen and antibody ELISAs were 93.3% and 100%, respectively. The traditional method detected 2 laboratories as outliers for HIV antigen testing and 3 laboratories as outliers for HIV antibody testing. The robust statistics method showed better discrimination of outliers, detecting seven laboratories as outliers for HIV antigen testing and six for HIV antibody testing. The outliers detected by the Youden plot were differentiated as six systematic and 2 random errors.ConclusionTherefore, the design of reliable EQAS based on HIV panels with varied and specified titers is prerequisites for quality improvement of HIV testing laboratories.     

What can be achieved in an external quality-assessment scheme with a small number of participants: four years of experience with thyroid-related tests in Israel

The Israel External Quality-Assessment scheme (EQAS) provided service from 1985 to 1989, primarily to laboratories in Israel. Participation was voluntary and confidential, and involved 30-35 laboratories performing thyroid-related function tests. Scheme design included 36 human serum specimens distributed to the participants at the beginning of each year. For 12 months, three specimens were analyzed each month and the results were reported to EQAS on pre-agreed dates. Monthly reports sent by EQAS to participants after analysis of the results included the overall consensus mean used as target value, between-laboratory agreement, individual laboratory bias, and recovery data. The overall consensus mean calculated as all-laboratory trimmed mean was validated by reproducibility and recovery studies. Samples with undetectable concentrations of thyrotropin (TSH), obtained from patients proven thyrotoxic, were used to validate measurement of very low TSH concentrations. During the scheme, liquid serum was found superior to lyophilized specimens for distribution to the participants. The scheme helped stimulate major improvements in between-laboratory agreement, especially for low TSH concentrations, with CVs decreasing from 180% in the first year to 20% in the fourth year. Each laboratory's performance also improved as judged by the median bias and variability of bias and by the considerable decrease in the number of laboratories with unacceptable performance for all tests. Method-related differences in performance were observed despite the small number of participants. Better methods, e.g., a radioimmunometric method for TSH, were detected and adopted by the participants, with concomitant improvement in performance. Transfer to analog procedures for free thyroxin, in addition to, but mostly instead of, thyroxin, was also documented, with no gain in analytical performance. Despite this being a small scheme, most of the goals achievable with a large scheme were realized.     

Results and feasibility of an external quality assessment scheme for self-monitoring of blood glucose

BACKGROUND: The analytical quality of self-monitoring of blood glucose (SMBG) is not satisfactory, and the need for standardized control routines for SMBG has been underscored. The objective of this study was to investigate whether an external quality assessment scheme (EQAS) designed for office laboratories could improve the quality of SMBG measurements. METHODS: From October 2001 through March 2004, we conducted 6 glucose surveys for diabetes patients and coordinated them with an EQAS for office laboratories. Patients received 2 control samples by post twice a year. They measured each control sample in duplicate in accordance with written instructions, returned the results, and received an assessment of their analytical performance. Participants who got a poor evaluation were followed up by phone and were offered guidance. RESULTS: Participating in an EQA program over a period of 3 years decreased the percentage of poor results among diabetes patients significantly, from 11.2% to 1.9% in the first and last surveys, respectively. Between-participant CVs improved from 5.5% to 3.7% and were comparable to results from office laboratories. It was difficult to sort out factors contributing to quality improvement. CONCLUSIONS: Implementing a traditional EQAS among diabetes patients may improve the analytical quality of SMBG and could be convenient for motivated patients. Further evaluation of the clinical usefulness of implementing such a program is needed, however, and costs as well as limitations of current EQAS for glucose in general should be taken into account.     

The United Kingdom National External Quality Assessment Scheme gating and standardization strategy for use in residual WBC counting of WBC-reduced blood components

BACKGROUND: Major causes of interlaboratory variation in low-level WBC counting are the gating strategies and staining methods employed. To overcome these limitations, a stable low-level WBC control preparation (termed daily run control [DRC]) was developed that when coupled with a new gating strategy will enable international standardization. STUDY DESIGN AND METHODS: Both a whole blood preparation (stability of more than 12 months; target WBC count of 20 cells/microL with defined fluorescence values) and a new gating strategy were developed and used with a staining kit (LeucoCOUNT [Becton Dickinson BioSciences] providing the basis for standardization). These were then combined and used to crosscalibrate seven different flow cytometers. After standardization with the DRC, comparative studies were undertaken with fresh samples with a WBC range of <1 to 60 cells per microL. RESULTS: The developed gating strategy enabled the DRC WBCs to be positioned to within four channels of the expected target fluorescence 1 value (2.3% variation) and within three channels of the target fluorescence 2 value (0.7% variation) on all evaluated instruments. Subsequent analysis of any sample meant that the WBCs always occupied the same "sample space," irrespective of flow cytometer platform and without the need for repositioning of the analysis region and/or gate. CONCLUSION: The cross calibration and standardization of flow cytometers used for low-level WBC counting (irrespective of platform) are attainable with this United Kingdom National External Quality Assessment Scheme strategy. Its adoption should reduce interlaboratory CVs and provide a practical approach for the rapid identification of operator and machine problems.     

External quality assessment in the measurement of haemoglobin by blood gas analysers in Belgium

OBJECTIVE: The Belgian national External Quality Assessment Scheme (EQAS) for haematology organized a survey to assess the reliability of haemoglobin (Hb) measurements with the blood gas analysers (BGAs) currently available in Belgian hospitals. MATERIAL AND METHODS: All hospital laboratories received two specimens of fresh EDTA anticoagulated whole blood and were asked to determine the Hb concentration using both the conventional haematology analyser (HA) and all BGAs in the hospital. Ninety-seven hospital laboratories participated in the study and a total of 166 results were reported. The BGAs used (grouped according to technology) were Rapidlab 845, 855, 865 (Bayer 1, n = 41), Rapidlab 1245, 1265, Rapidpoint 405 (Bayer 2, n = 19), GEM Premier 3000 (Instrumentation Laboratory, IL, n = 13), ABL 500 and 600 series (Radiometer 1, n = 13), ABL 700 and 800 series (Radiometer 2, n = 35), Omni C, S5 (Roche 1, n = 7), Omni 3, 6, 9, S2, S4, S6 (Roche 2, n = 21). RESULTS: For the BGAs from Bayer, Radiometer and Roche, interlaboratory variation ranged from 0.6 % to 4.1 %, indicating good precision and close agreement between centres. A significant negative bias observed on the GEM Premier 3000 using the EDTA anticoagulated blood samples did not appear to be present in fresh heparinized whole blood samples. There was no significant difference in imprecision and bias between Hb measurements on BGA situated in and outside the central laboratory.     

TPPA在梅毒临床血清学诊断和室间质评中的应用

目的评价TRUST和TPPA在梅毒血清学诊断和室间质评中的价值。方法采用TRUST和TPPA检测80例梅毒患者和67例非梅毒患者血清;1998～1999年采用TRUST检测室间质评样本,从2000年开始采用TPPA检测室间质评样本。结果梅毒患者TRUST和TPPA阳性率分别为86.3%(69/80)与100%;TRUST在室间质评样本中的敏感性44.44%,特异性90.00%,符合率68.75%,而TPPA的敏感性、特异性、符合率达到100%。两者的敏感性存在明显差别(χ2＝9.35,P＜0.01)。结论TPPA具有很高的敏感性、特异性,可作为临床诊断梅毒的首选方法。     

Automatic erythrocytometry in a robotized microscope MEKOS-Ts1

Measurements of the form and size of erythrocytes are needed in the diagnosis of a number of diseases. However, such measurements, if made manually, are a labor-consuming and often inaccurate method, which ensures the determination of a very limited number of parameters. Hardware/software unit MEKOS-C1 enables an automated examination of blood smear, thus speeding up significantly the analysis and ensuring a more complete and accurate information. The possibilities of unit MEKOS-C1 were evaluated for the diagnosis of ovalocytosis. Blood smears of 19 patients from the Russian Pediatric Clinical Hospital, including 8 patients with inherited ovalocytosis, 1 patient with spherocytic ovalocytosis and 10 patients without the disease, were made use of Erythrocytes were isolated in the images of preparations and the contour of each cell was approximated by ellipse. The ratio between ellipse semi-axes served as a measure of erythrocytes' ovality. The mean ratio of semi-axes (RS) and the index of ovalocytosis (IO), i.e. a ratio of the mean maximum diameter to the mean minimal diameter, were calculated for each smear. Manual IO measurements were made in all preparations as a control. Since an additional error can enter the result because of the irregular smear nature and impossibility to standardize completely the technology of smear preparation, the data, obtained from two different smear parts and from parallel preparations, were compared. The reliability, stability and good reproducibility of the automated measurement results were demonstrated. The mean erythrocytes' RS correlated well with IO, obtained manually, and did not virtually differ from RS, measured in the automated manner. The mean RS value of erythrocytes, obtained from patients with inherited ovalocytosis, significantly differed from the control values, which is indicative of a high information density of the discussed parameter. Therefore, RS, when measured automatically, is a reliable and convenient characteristic of erythrocytes' ovality under the conditions of using the ordinary technique of smear preparation.     

The peripheral smear

The CBC "with differential" presently includes a blood smear that is examined by the medical technologist and is available for the physician. With increased familiarity of the technique for blood smear preparation and interpretation, the emergency physician must include peripheral blood smear review as part of the emergency department evaluation of bleeding disorders, anemia, infectious disorders, and suspected leukemia. Knowing the variations in morphology of blood cells in specific disease states should help the physician to intelligently order and meaningfully interpret the peripheral blood smear. It is a test commonly available but awaits full use by physicians in emergency medicine.     

上海地区肿瘤标志物室间质量评价中允许总误差适宜性的探讨

目的分析上海地区肿瘤标志物室间质评的方法变异及实际允许误差范围,并比较与不同国际标准及生物学变异要求提供的允许总误差(TEa)的差异,探讨上海地区肿瘤标志物TEa设置对当前分析质量水平的适宜性。方法以上海市2010至2012年的肿瘤标志物室间质量评价的数据为基础,计算不同方法组在6次室间质评计划中30个样本的合成变异系数(CV),根据合成CV计算上海地区肿瘤标志物室间质评的实际TEa,比较其与德国Rilibak质控指南、澳大利亚皇家病理学会(RCPA)质量要求和生物学变异数据合成的TEa的差异。结果在6次室间质评计划中,血清甲胎蛋白(AFP)、癌胚抗原(CEA)、糖类抗原(CA)125、CA153、CA19-9、前列特异性抗原(PSA)的实际TEa分别为22.63%、22.43%、19.30%、21.56%、27.43%和19.55%,与Rilibak的TEa比较接近,能达到生物学变异数据合成的适合水平的TEa要求,但高于RCPA的TEa范围。结论上海地区的肿瘤标志物室间质评计划的实际TEa水平接近或符合德国Rilibak的要求,略低于比较严格的澳大利亚RCPA的TEa要求,TEa设置方法能够满足当前的质量水平分析。     

血细胞自动化分析后血涂片复审标准制定的原则与步骤

根据血细胞分析方法的变迁和仪器法血细胞检测后血涂片复审的现状,结合血涂片复审41条国际规则,介绍临床实验室制定血涂片复审标准的原则和步骤,以及值得注意的问题.     

Diagnosis of DiGeorge and Williams syndromes using FISH analysis of peripheral blood smears.

We describe the use of a FISH protocol for detecting chromosome microdeletions in peripheral blood smear leukocytes. This method has the advantage of a smaller sample requirement than classical metaphase chromosome analysis and the potential for analysis of a larger number of chromosome microdeletions using a routine blood smear. A selected series of 10 DiGeorge syndrome (DGS) and 12 Williams-Beuren syndrome (WBS) patients were correctly diagnosed by this method confirming results obtained by molecular cytogenetic metaphases. These results support effectiveness of interphase FISH analysis on peripheral blood smears as a focused, single-step method for the detection of chromosome microdeletions.     

Frequently asked questions at the Quality Control Centre Switzerland (CSCQ)

The Quality Control Centre Switzerland (CSCQ) is one of two National EQAS organisers for the medical laboratory. Frequently asked questions at the CSCQ from two time periods have been analysed and compared. They form one of the sources for continuous improvement. It turns out that question frequency per se is not a criterion for the intended purpose. Well formulated single questions or remarks from different sources, together with the institutionalized practice of process evaluation, can lead to specific measures.