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At least 271 records · Page 15Linked to original sources
PubMed1994

Quality control in ultrasound studies on atherosclerosis.

This review discusses the quality control of equipment and technician performance in long term, multicentre trials using ultrasound detection and quantification of atherosclerosis. Examples on how such quality control measures could be implemented are given. Based on our own experience and that of other groups we suggest the following items as being important when planning for quality control in this type of study. 1. Write down the specifications demanded with regard to the ultrasound equipment and reading stations. 2. Compare the commercially available equipment on those characteristics by means of in-vitro and/or in-vivo testing. 3. Select the most suitable equipment for all centres and check it before shipping. 4. Sign a full maintenance agreement for all centres. 5. Evaluate the ultrasound devices and reading stations regularly during the study using phantoms. 6. Train sonographer and readers thoroughly before the start of the study. Certify those who successfully complete the training programme and demonstrate proficiency in scanning or reading. 7. Determine each sonographer's/reader's variability before and repeatedly during the study. Give feedback on performance to the sonographer/reader. 8. Create a regular retraining programme for all sonographers/readers and extend for those with poor performance. 9. Feed all the above information to a Data Quality Control Committee, having the ultimate responsibility for the quality control in the study.

Arteriosclerosis↗
PubMed2004

Serial correlation of quality control data--on the use of proper control charts.

BACKGROUND: Biochemical quality control (QC) data have been reported to be autocorrelated. Serial correlation may increase the rate of false alarms if the traditional exponentially weighted moving average (EWMA) control chart to monitoring the process mean is used. False alarms are the focus of this paper, where an alarm is defined as the occurrence of a QC value outside the three standard deviation control limits. METHODS: Daily QC measurements of common biochemical (Vitros 500) and hematological (SF-3000 and Behring Coagulation Timer (BCT)) quantities were recorded during several months while methods and analyzers showed no signs of malfunctioning. The time series were examined for autocorrelation and the performance of the EWMAST chart was compared with that of the EWMA chart when autocorrelation was present. RESULTS: Many of the time series showed significant signs of autocorrelation. Using the EWMA chart to monitor the process mean, false alarms were noted for positively autocorrelated time series, while this was seldom the case when the EWMAST chart was used. For some quantities, the EWMAST chart gave alarms. However, when the process autocorrelation and therefore the limits of the control chart were updated, the alarms given by the EWMAST chart were reduced or disappeared. In some cases the mean level changed over time, which is expected due to calibrations. This problem will be the topic of a subsequent paper. CONCLUSIONS: Positive autocorrelation may be present in QC data. In this case the EWMAST chart should be used in place of the EWMA chart.

Algorithms↗
PubMed1993

Standardization and quality control of quantitative microscopy in pathology.

Standardization and quality control of quantitative microscopy techniques are distinct but related concerns. The first deals with the great variety of quantitative methods, measured features, and even response variables used in investigation of biological or clinical processes. The latter deals with reproducibility of results from those investigations across time and test performance sites. Though distinct, efforts for standardization and quality control are inherently interactive. Consensus on standard methods, instrumentation, and data analysis is hard to achieve in fields developing as rapidly as quantitative microscopy. Consensus is possible, however, on the issues that affect test performance and interpretation. For example, issues of specimen type, fixation, processing, and staining affect image cytometry just as they do flow cytometry. Raw data acquisition issues include area sampling rules and fidelity of optical and sensor systems (light wavelength, glare/stray light, lens aberrations, numerical aperture, depth of focus, scan precision, pixel spacing and depth, sensor linearity, and stability). Intermediate data issues are primarily related to image foreground/background segmentation techniques--automated versus manual, object-specific versus field-based. Data reduction and interpretation procedures also provide many roads for divergence from uniformity. Each of these issues must be considered in terms of its effect on comparability and utility of quantitative microscopy results. Quality control for quantitative microscopy is as important as standardization for its use in research programs and with clinical specimens. The sine qua non of quality control is comparison of experimental results against a known "correct" value to estimate accuracy, and against other experimental results to estimate precision.(ABSTRACT TRUNCATED AT 250 WORDS)

Colonic Neoplasms↗
PubMedDate not supplied

A simplified method for quality control of deglycerolized erythrocytes.

Quality control to detect inadequately deglycerolized red blood cells can be easily and inexpensively accomplished by suspending the deglycerolized cells in either recipient serum or normal saline in the same way in which the routine crossmatch is performed. In vitro hemolysis is readily and consistently apparent when the residual glycerol exceeds either 2.4% (in saline) or 2.5% (in serum). In contrast to generally held beliefs, the in vivo 24-hour survival of red blood cells with a residual glycerol concentration of up to 2.7% was demonstrated to be 76% of greater, a level which is well above what is usually accepted as adequate.

Blood Transfusion↗
PubMed2003

Ibuprofen quality control by electrochromatography.

The quality control of drugs is generally made by HPLC. This control could be made also by capillary electrochromatography (CEC). In this paper we report the analysis by CEC of ibuprofen, a well-known anti-inflammatory non steroidic drug, and some of its impurities. The analyses were performed in a 100-microm inner diameter (I.D.) fused silica capillary, packed with RP-18 stationary phase. The mobile phase was a mixture of 100 mM formic acid solution (pH 2.5), water and acetonitrile (ACN). The ACN percentage in the mobile phase and the applied voltage were carefully studied to well resolve the drug from each impurity. The results, obtained determining ibuprofen and related compounds by CEC, showed the selectivity and efficiency of the method.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2006

[Development of modern tissue banks and quality control].

OBJECTIVE: To review the development and quality control of modern tissue banks. METHODS: The rules, regulations and the management literatures about tissue banks were extensively and comprehensively reviewed. RESULTS: Tissue banks have a significant progress and are developing to concentration, industrialization and standardization gradually. Quality control is being paid more attention in modern tissue banks. CONCLUSION: Modern tissue banks will have a good future and the quality control must be intensified.

Blood Banks↗
PubMed1975

Quality control in diagnostic virology.

Quality control in diagnostic virology is in its infancy and some preliminary investigations are reported. Simulated specimens containing viruses have been prepared and distributed so that they could be included in the routine work of virus isolation in participating laboratories. Sera containing antibodies to rubella and influenza virus have also been sent to laboratories for testing. Laboratories were able to check their results immediately after the closing date, and could compare their performance with that of other laboratories when the analysis of each distribution was circulated. The results so far show considerable variation in performance and indicate that there is room for improvement in some laboratories. There is no evidence to show whether the exercise has had any effect on the practice of virology in participating laboratories but some baselines have been produced for comparison with the results of investigations in the future.

Antibodies, Viral↗
PubMed1998

Levels of cytokines and immune activation markers in plasma in human immunodeficiency virus infection: quality control procedures.

Procedures for quality control (QC) in a laboratory that concentrates on cytokine and soluble marker measurements in biological fluids are outlined. Intra-assay, interassay, and interlaboratory experiences are presented. Plasma and serum beta2-microglobulin (beta2M) and neopterin test data are presented in greatest detail, along with substantial tumor necrosis factor alpha (TNF-alpha), gamma interferon, soluble interleukin-2 receptor-alpha (sIL-2Ralpha), sTNF-RII, IL-4, and IL-6 data. Recommended QC procedures for cytokine and soluble-marker testing include replicate testing of two or more reference samples provided by the kit manufacturer, replicate testing of in-house frozen reference QC samples that represent normal and abnormal analyte contents, retesting 15 to 20% of randomly selected samples, and comparing normal reference ranges each year. Also, eight cytokines and soluble markers were evaluated in human immunodeficiency virus (HIV)-seronegative and HIV-seropositive individuals stratified on the basis of CD4 T-cell numbers. Levels of some but not all cytokines in serum increased in HIV infection. There was a tendency for cytokines to increase with more advanced disease, defined by reduced CD4 T-cell numbers. Cytokine changes did not relate closely to CD4 level, indicating that separate information was provided by the measurements of TNF-alpha, sTNF-RII, sIL-2Ralpha, beta2M, and neopterin. Serum IL-4 and TNF-alpha levels were not increased. The quality of laboratory data can impact on clinical relevance. Interlaboratory comparisons revealed substantial differences at some sites and documented the need for external proficiency-testing quality assurance programs.

Biomarkers↗
PubMed1983

Synthetic materials for platelet quality control.

At present, the quality control of platelet counting by semi-automated and automated methods does not meet ideal standards. Controls prepared from human or animal platelets have limited stability, and some synthetic platelet controls that are available do not have the size distribution of fresh platelets. The platelet control materials described here are wholly synthetic; however, their particle size distribution is like that of normal human platelets, and the dispersing medium has the viscosity and surface tension of plasma. Two types of products are described. The first type are dilutions of the synthetic platelets which are handled like 3000-fold dilutions of platelet-rich plasma and are intended for direct use on instruments like the Coulter ZBI. The two dilution levels gave counts of about 50,000 and 200,000/microL on the Coulter ZBI and were found to be stable for at least 30 days at - 20C, 4C, and 37C, and at least eight months at 25C. The second type of product is handled like whole blood and is intended for direct use on instruments like the Coulter Model S-Plus. This product gave counts of about 200,000/microL and was found to be stable for at least 120 days at - 20C, 4C, 25C, and 37C. Freezing at - 20C produced some aggregates that dispersed after thawing and standing for several days prior to testing.

Autoanalysis↗
PubMed2006

Rapid prescreening of Papanicolaou smears: a practical and efficient quality control strategy.

BACKGROUND: Efficient quality control (QC) is essential to ensure high sensitivity of Papanicolaou (Pap) smears. For this purpose, rescreening of 10% random negative smears is ineffective. Rapid rescreening (RR) of all negative Pap smears is more practical and has received widespread acceptance, especially in Europe, although its sensitivity is difficult to monitor and its retrospective nature may influence the vigilance of the screeners. The method of rapid prescreening (RPS) overcomes these drawbacks because rapid review of Pap smears occurs before routine full screening. METHODS: All routine conventional Pap smears over 2 months underwent RPS by 12 cytotechnologists. Approximately 30 seconds were allowed to prescreen each slide. The presence of abnormal cells (atypical squamous cells of undetermined significance [ASCUS] or above), infection or endometrial cells detected on RPS was documented. All slides subsequently underwent routine full screening. Results of both screening methods were compared. RESULTS: Of a total of 8364 Pap smears, 310 (3.7%) cases were categorized as abnormal after final diagnosis. Of those, 135 were also detected on RPS (sensitivity of 43.5%). Seventeen abnormal cases were detected only on RPS: these consisted of 13 ASCUS cases, 3 low-grade squamous intraepithelial lesions, and 1 high-grade squamous intraepithelial lesion. The sensitivity of RPS for infections and endometrial cells was 51.6% and 28.3%, respectively. Implementation of RPS did not significantly impact the work flow in our laboratory. CONCLUSIONS: RPS is an efficient and practical QC tool. It is a reliable method with which to monitor sensitivity and reduce the false-negative rate, and because it is done before finalizing the case, it allows for timely corrections to the diagnosis and avoids the need to amend reports.

False Negative Reactions↗
PubMed1983

Stability of mean assay values of magnesium and iron in lyophilized quality control serum: a study based on data from the quality assurance service (QAS) of the College of American Pathologists.

Data from magnesium and iron analyses of pools of lyophilized quality control serum were used to evaluate stability of analyte mean values in the pre-reconstitution period. Information was received from laboratories in Regional Quality Control Programs between 1977 and 1981, using CAP Quality Assurance Service data processing. For magnesium, 28 of 41 (68%) pool-method combinations were stable, 11 (27%) showed decreases, and 2 (5%) showed increases. Decreases averaged 0.008 mg/dL/month (all methods). A pronounced effect of method (automated methylthymol blue) and year correlated with decreases in measurable magnesium. For iron, 45 of 56 (80%) pool-method combinations were stable, 8 (15%) showed decreases, and 3 (5%) showed increases. Decreases averaged 0.349 g/dL (all methods). In most cases, changes in measured concentrations are attributed to methodologic factors, rather than intrinsic changes in analyte concentrations.

Autoanalysis↗
PubMed2002

Quality control in nucleic acid testing--where do we stand?

Quality control has been playing an increasingly important role in the implementation of nucleic acid amplification techniques (NATs) for clinical diagnosis since the introduction of these methods in the early 1990s. Initial multicenter studies involving hepatitis B virus (HBV), hepatitis C virus (HCV), Mycobacterium tuberculosis, and human immunodeficiency virus type 1 (HIV-1) revealed serious problems in specificity (false-positive rates of ca. 40%) and sensitivity, large variations in quantitative results, and a plethora of units (largely not comparable between assays). The problem areas identified included the need for standardized reagents and common units, contamination control mechanisms, inhibition control mechanisms, genotype-independent detection and quantitation, facilitated nucleic acid isolation procedures, clinically relevant dynamic ranges, and internal run controls. Progress made in each of these areas will be discussed. In addition to the above-mentioned problem areas, the value of external quality control of existing and evolving NATs was recognized. To this end, the European Union Quality Control Concerted Action for Nucleic Acid Amplification in Diagnostic Virology was established in May 1998. During its three-and-a-half years of existence, a total of 14 proficiency panels containing 8-13 well-characterized, simulated clinical samples of various viral loads and genotypes were prepared for herpesviruses (herpes simplex virus, human cytomegalovirus), blood-borne viruses (HBV, HCV, HIV-1), enteroviruses, and Chlamydia trachomatis, distributed to up to 20 different countries, and tested by up to 97 different laboratories. The results show dramatic improvement in specificity (false-positive rates <3% for most panels), presumably due to a generally greater expertise of participating laboratories, more frequent use of enzymatic or mechanical contamination control mechanisms, and increased utilization of standardized reagents (commercial kits). However, considerable problems with sensitivity remain (false-negative rates up to 50%), reflecting the high detection limits of some commercial viral load kits still on the market as well as inadequate standardization of quantitation controls between assay systems. In conclusion, although considerable progress has been made, quality control of NATs in clinical diagnosis remains an ongoing challenge.

Insurance, Health, Reimbursement↗
PubMed1985

Quality control for estrogen and progesterone receptor assay in human breast cancer: the influence of computation methods on intra and interlaboratory variability.

The importance of evaluating receptors for estrogen and progestin in human breast cancer has been pointed out by many authors. In the absence of a reference standard, receptor assays must be controlled by intra and interlaboratory quality control programs. Much interlaboratory variability exists due to non-uniform analytical protocols, non-uniform ligands, intrinsic errors and also errors in computation methods. The goals of our Italian Quality Control Program on Multicenter Trials are to standardize the analytical procedures and computation methods. Twenty Italian laboratories participated in the Quality Control Program. Each specimen was assayed for steroid receptor content according to the standardized dextran-coated-charcoal method. Data were subjected to computerized analyses by 5 different methods of calculation (Scatchard plot, direct plot, Lineweaver-Burk method, Brunauer-Emmet-Teller analysis, single-point approach). The results were than evaluated to identify intra- and inter-assay variation coefficients and to define other statistical parameters. The authors suggest different calculation methods depending on the specific experimental and/or physiopathological conditions.

Breast Neoplasms↗
PubMed2002

Neurotransmitter metabolites in CSF: an external quality control scheme.

We report an international external quality control scheme on neurotransmitter metabolites in cerebrospinal fluid (CSF). The neurotransmitter metabolites homovanillic acid (HVA), 5-hydroxyindoleacetic acid (5-HIAA) and 3-methoxy-4-hydroxyphenylglycol (MHPG) are analysed to diagnose inborn errors of neurotransmitter metabolism. HVA is the catabolite of dopamine; 5-HIAA is the catabolite of serotonin; and MHPG is the catabolite of noradrenaline. In the first phase, 12 laboratories from six countries participated in this special quality control scheme to define the present state of the art and achieve harmonization in analytical outcome and interpretation. In the second part, recoveries, dilutions and methods for sample preparation were compared. The results of 3 of 12 laboratories were excluded because of unacceptable intralaboratory coefficients of variations (CV) for HVA and/or 5-HIAA. The inter- and intralaboratory CVs, the linearity and the recovery were acceptable for the other laboratories for both parameters. Unacceptable differences in the reference ranges between laboratories, leading to differences in interpretation of the results, became obvious. There was a significant improvement of the interlaboratory CV for HVA after standardization with a calibrator. The reproducibility of MHPG measurement appeared to be adequately established in only two laboratories and recovery was low in all five measuring this metabolite. The quality control scheme is an invaluable tool for controlling the analytical outcome and providing support to laboratories to improve their quality.

Algorithms↗
PubMedDate not supplied

A CD-ROM prototype of a multimedia-based interactive tool and guide, to perform quality control tests for the computed tomography scanners.

Quality control tests for CT scanners are very important for correct machine performance, and for the radiation protection of patients and medical personnel. As proliferation of CT scanners continues, the need for distributable software tools to perform quality control tests becomes evident. A multimedia tool and guide will help medical physicists and technologists to perform these tests easily and correctly. The guide can be easily accessible in CD-ROM, or networked on the Internet. The user, medical physicist or technologist, can find in the present guide the pertinent theoretical information and the procedures necessary to perform the quality control tests, with the help of texts, CT images and photographs, narration and video. The results of the tests are automatically compared with machine specifications and acceptable values set by international bodies, and are stored in a table.

CD-ROM↗
PubMed1995

The impact of quality control on radiography in general dental practice.

The aim of this study was to assess the impact of two quality control measures upon the quality of periapical radiographs in general dental practices. Five general dental practitioners took part in the study. Periapical radiographic quality was assessed before and after the introduction of film holders and quality control measures for processing. Prior to the introduction of the quality control measures, 49% of radiographs were assessed as being 'unacceptable', 49% exhibited faults but were 'acceptable' for diagnostic purposes, while only 2% of radiographs were 'excellent' being entirely free of faults. After the introduction of film holders and processing quality control procedures 39% were 'unacceptable' (P < 0.05), 56% were 'acceptable' and 5% of radiographs were classified as 'excellent'. It is concluded that current recommendations to dentists to use film holders and to carry out processing quality control are justified in terms of an improvement in the diagnostic quality of radiographs. However, improvements in undergraduate and continuing education for all members of the dental team, with emphasis on practical 'hands-on' instruction, may improve the effectiveness of these recommendations.

Chi-Square Distribution↗
PubMed1990

Method for quality control of laboratory tests using histograms of daily patient data.

A method for controlling the quality of laboratory tests is proposed. Histograms of patients' daily results which fall within reference ranges of healthy individuals are used for estimating accuracy and precision of measurements. For the determination of accuracy, three methods are evaluated; computing an average of patients' results; determining the location of the peak of the histogram; approximating the histogram by an Erland distribution and determining the peak of the distribution. For precision control, standard deviations are calculated from patient data. We applied these methods to serum aspartate aminotransferase (AST or SGOT) and total cholesterol of patients in a general hospital. Averages, peaks of approximated Erland distribution, and standard deviations were found to be useful to daily quality control in laboratories of large hospitals.

Aspartate Aminotransferases↗
PubMed2005

Quality control of equipment in home mechanical ventilation: a European survey.

Quality control of the equipment used in home mechanical ventilation is necessary in order to ensure that patients safely and accurately receive the prescribed ventilatory support. The aim of this study was to carry out a survey on the quality-control procedures in different centres and countries. The survey was carried out in the context of a European Commission Concerted Action covering 16 European countries. The study was extensive and detailed, involving 326 centres, which provided home ventilation to >20,000 patients. The survey showed that: 1) ventilator servicing was mainly carried out by external companies (62% of centres), with a servicing frequency ranging 3-12 months; 2) interaction between servicing companies and prescribers was limited (only 61% of centres were always informed of major incidents); 3) participation of centres in equipment quality control was poor (only 56% of centres assessed that patients/caregivers correctly cleaned/maintained the ventilator); and 4) centres were insufficiently aware of vigilance systems (only 23% of centres). Moreover, the data showed considerable inter- and intra-country differences. The size of the centre was an important determinant of many of these quality-control aspects. This survey provides information that will enable the European Commission Concerted Action to formulate recommendations on procedures for home-ventilator quality control.

Chronic Disease↗