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Results for “quality control”

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At least 613 records · Page 34Linked to original sources
PubMed1987

Time, a quality-control parameter in flow cytometry.

Time has been used as a quality-control parameter in our flow cytometer. This parameter was automatically incorporated into the list-mode data base by hooking the computer clock directly into the acquisition logic. Quality control can then be checked by "replaying" fluorescence or light scatter data vs. time and any instrumental drift can be observed and degraded data can be excised. The technique is illustrated with a number of DNA data sets from a tissue culture cell line in which artificial perturbations were introduced during data acquisition to simulate potential causes of instrumental drift.

Cell Line↗
PubMed2003

Quantitative quality control in microarray experiments and the application in data filtering, normalization and false positive rate prediction.

Data preprocessing including proper normalization and adequate quality control before complex data mining is crucial for studies using the cDNA microarray technology. We have developed a simple procedure that integrates data filtering and normalization with quantitative quality control of microarray experiments. Previously we have shown that data variability in a microarray experiment can be very well captured by a quality score q(com) that is defined for every spot, and the ratio distribution depends on q(com). Utilizing this knowledge, our data-filtering scheme allows the investigator to decide on the filtering stringency according to desired data variability, and our normalization procedure corrects the q(com)-dependent dye biases in terms of both the location and the spread of the ratio distribution. In addition, we propose a statistical model for false positive rate determination based on the design and the quality of a microarray experiment. The model predicts that a lower limit of 0.5 for the replicate concordance rate is needed in order to be certain of true positives. Our work demonstrates the importance and advantages of having a quantitative quality control scheme for microarrays.

Algorithms↗
PubMed1991

Bhattacharya: a new application for quality control.

The Bhattacharya method and the 'average of normals' method for internal quality control were compared. Both are based on unselected patient test results. The Bhattacharya method is mostly used in clinical chemistry for calculation of reference intervals but could be modified for quality control procedures. Using the data of a coagulation test and stimulating systematic errors, it was concluded that the Bhattacharya method is more sensitive to expected shifts and is more flexible than the 'average of normals' method.

Blood Coagulation Tests↗
PubMed2005

[Highly quality-controlled radiation therapy].

Advanced radiation therapy for intracranial disease has focused on set-up accuracy for the past 15 years. However, quality control in the prescribed dose is actually as important as the tumor set-up in radiation therapy. Because of the complexity of the three-dimensional radiation treatment planning system in recent years, the highly quality-controlled prescription of the dose has now been reappraised as the mainstream to improve the treatment outcome of radiation therapy for intracranial disease. The Japanese Committee for Quality Control of Radiation Therapy has developed fundamental requirements such as a QC committee in each hospital, a medical physicist, dosimetrists (QC members), and an external audit.

Antineoplastic Agents, Alkylating↗
PubMed2003

A novel strategy for microarray quality control using Bayesian networks.

MOTIVATION: High-throughput microarray technologies enable measurements of the expression levels of thousands of genes in parallel. However, microarray printing, hybridization and washing may create substantial variability in the quality of the data. As erroneous measurements may have a drastic impact on the results by disturbing the normalization schemes and by introducing expression patterns that lead to incorrect conclusions, it is crucial to discard low quality observations in the early phases of a microarray experiment. A typical microarray experiment consists of tens of thousands of spots on a microarray, making manual extraction of poor quality spots impossible. Thus, there is a need for a reliable and general microarray spot quality control strategy. RESULTS: We suggest a novel strategy for spot quality control by using Bayesian networks, which contain many appealing properties in the spot quality control context. We illustrate how a non-linear least squares based Gaussian fitting procedure can be used in order to extract features for a spot on a microarray. The features we used in this study are: spot intensity, size of the spot, roundness of the spot, alignment error, background intensity, background noise, and bleeding. We conclude that Bayesian networks are a reliable and useful model for microarray spot quality assessment. SUPPLEMENTARY INFORMATION: http://sigwww.cs.tut.fi/TICSP/SpotQuality/.

Algorithms↗
PubMed1998

[Analysis on quality control of drug susceptibility testing in the surveillance of drug resistance in tuberculosis in Henan].

OBJECTIVE: To evaluate the working quality of Henan province reference laboratory(PRL) in the surveillance of drug resistance (DRS) in Henan. METHOD: West Pacific Regional (WPR) Supranation Reference Laboratory(SRL) in South Korea conducted three times of quality control of drug susceptibility testing (DST) from SRL to PRL and to national reference laboratories(NRLs) in the region at the same time, and once of which from PRL to SRL. The exchanging strains of M. tuberculosis, which were clinical isolated ones containing both drug susceptible and drug resistant cultures, were tested for resistance to SM, INH, RFP and EMB. The DST procedure was proportion method, and L-J medium was used. RESULT: It was shown that the sensitivities for most of the four drugs in the three times of DST quality control from SRL to PRL were higher than their specificities, and that the sensitivities for both INH and RFP were 100%. And the accuracy, or agreement, for both INH and RFP was more than 90%, except for that of RFP in the first time. Compared with the results from SRL to NRLs (including Henan PRL), except for the specificity for SM in WPR being higher than that in Henan (84% versus 70%, P < 0.05), there was no significant difference between Henan and WPR on the specificity and sensitivity of the other drugs. Similar characteristics can be found in the results from PRL to SRL. And the efficiency for SM, INH and RFP was all higher than 90%. CONCLUSION: The quality control on Henan PRL meet the requirement of the WHO/IUATLD guidelines for surveillance of drug resistance in tuberculosis(1997).

Antitubercular Agents↗
PubMed1995

Quality assurance and quality control of an intensive care unit picture archiving and communication system.

Most radiology departments have established quality assurance (QA) and quality control (QC) programs for conventional film-based image management systems. At many institutions, digital image management systems, or picture archiving and communication systems (PACS), are replacing part or all of the film management system. In these situations, it is important to control the quality of the digital images that are produced. The observed frequency of eight types of image-related errors occurring on an image viewing station located in a medical intensive care unit is reported. Images on the viewing station were checked for 12 consecutive weeks. Film images available in the radiology reading room and digital images on the viewing station were compared with a list of completed examinations produced by the radiological information system. Overall, 1,082 patient examinations were encountered. Seventy-six images (7.02% of all images) were observed with errors. In addition, four previously unencountered types of errors were observed in 11 images (1.01% of all images). The majority of the errors are attributed to interfaces either between information systems or between the PACS and the user. It is concluded that QA-QC procedures are necessary for PACS, and that good interfaces, both between information systems and between humans and computer systems, are essential for successful PACS implementations.

Humans↗
PubMed1995

Quality control of inhomogeneity correction algorithms used in treatment planning systems.

PURPOSE: This quality control program has been carried out under the auspices of S.F.P.H. (Socíete Fraņcaise des Physiciens d'Hôpital), to evaluate the performances of radiotherapy treatment planning systems (RTPS) used by different institutions. The aim of this Quality Assurance Programme was: (a) to set up a methodology to assess globally the capability of a given system to perform inhomogeneity corrections in the irradiated medium with external photon beams; (b) to analyze the limitations of the algorithms presently used and especially the two-dimensional (2D) dose calculation possibilities; (c) to check, on a number of systems in clinical use, the validity of the method and the variation of the results as compared to measurements used as reference. METHODS AND MATERIALS: Phantom (lung equivalent material placed into polystyrene) measurements, using cobalt-60 radiation, were carried out by the authors. The phantoms were circulated among the participating institutes to be scanned, and used as input to the treatment planning computer. RESULTS: Ten systems were tested in this study, using seven different inhomogeneity correction algorithms implemented in nine different TPS; four of these algorithms are used in a pixel by pixel basis and five of them in a contour basis. Significant discrepancies or inconsistencies have been observed even for sophisticated models supposed to be mostly accurate. CONCLUSION: The proposed tests and the experimental data provided are very useful as part of a quality-control program. They should be included in the initial extensive validation of TPS before starting clinical use, and should be repeated at regular intervals and at each updating of the program. They have the merit of including the whole procedure, from patient data acquisition to dose distribution printout.

Algorithms↗
PubMed1997

Long-term quality control of DXA: a comparison of Shewhart rules and Cusum charts.

Long-term clinical trials using bone mineral density (BMD) measurements are now commonplace. It is important to maintain a high standard of quality control. In this study two methods of monitoring quality control measurements of dual-energy X-ray absorptiometry (DXA) equipment have been compared using receiver operating curve (ROC) analysis: Shewhart multi-rule charts and Cusum charts. Computer-generated faults within daily spine phantom measurements were used. The Charts were then applied to 3 years of quality control data from one machine and the results related to hardware faults, random events and changes in the underlying BMD measurement. In the ROC analysis the Shewhart multi-rule chart performed as well or better than the cusum chart, but the stringency of the rules must be tightened to obtain optimal performance.

Absorptiometry, Photon↗
PubMed1999

[National quality control of serologic HLA typing].

Since 1995 the Istituto Superiore di Sanità, in collaboration with the Italian Red Cross, has been organising annually the quality control of serological HLA class I and II typing on histocompatibility laboratories which perform typing for organ and bone marrow transplantation. Improvement has been obtained every year; in fact, results of the 1997 control show that the 77% of the laboratories typed the major specificities correctly. Despite the remarkable improvement achieved during the first three years of quality controls, a new organisation has been designed for further years to ensure the participation of all the Italian laboratories (more than 100) and to promote a quality control scheme that will be acceptable at international level.

Accreditation↗
PubMed1998

Product quality control testing for the oral polio vaccine.

A brief overview regarding the quality control testing of the Sabin oral polio vaccine is provided. Product testing procedures and specifications are established through product license agreements between the vaccine manufacturer and the FDA Center for Biologics Evaluation and Research. The manufacture and testing of ORIMUNE is a multi-stage process that is closely monitored by the FDA following explicit protocols and requires extensive quality control testing at various stages.

Animals↗
PubMed2000

The development of a continuous quality control programme for strict sperm morphology among sub-Saharan African laboratories.

Inter-technician and between-laboratory differences, especially during the evaluation of sperm morphology, have been a major cause of concern. The study aimed to develop an intensive training programme with intervals of continuous quality control assessments for sperm morphology. Twenty andrology laboratories from sub-Saharan Africa were invited to participate in a World Health Organization Special Programme of Research, Development and Research Training in Human Reproduction semenology workshop. Following intensive training in strict sperm morphololgy evaluation, a continuous quality control programme was introduced on a quarterly basis. At baseline, the mean (+/- SD) percentage difference reported between the participants and the reference laboratory reading was 33.50 +/- 11%. After training, the mean percentage difference had decreased to 14.32 +/- 5% at 3 months and to 5.00 +/- 5% at 6 months. Pairwise comparison of the differences at each evaluation time revealed the following: Baseline differences (pre-training) differed significantly from the differences at 3 months (P = 0.0002) as well as at 6 months after training (P = 0.007). The differences at 6 months did not differ significantly from those at 3 months (P = 0.27). Training of andrology technicians as well as continuous proficiency testing can be conducted on a national and international level with the support of a referring laboratory. Global quality control measurements in andrology laboratories should become mandatory, since these results indicate that continuous quality control for laboratory technicians can be highly successful.

Africa, Northern↗
PubMed1993

[Experimental quality control of biopsy cannulas].

To examine the quality and comparability of biopsy needles. 310 biopsy needles of 40 types were examined microscopically and their suitability for penetrating tissues were studied. For this purpose the pressure required to penetrate a phantom was evaluated. The results were correlated with the diameter, design and construction. 50 of the 310 needles (16%) showed faults on microscopic examination. Measurements of identical needle types within a single production run showed variations in penetration pressures up to 330% (measured as force required for penetration), the average variation was 88%. The results show that the quality of biopsy needles is not constant and leaves something to be desired. To what extent variations in quality affect the biopsy material cannot be estimated. Nevertheless, the present results indicate that stricter quality control of biopsy needles is desirable.

Biopsy, Needle↗
PubMed1977

Long-term stability of enzymes, total protein, and inorganic analytes in lyophilized quality control serum.

The stability of total protein and various enzyme and electrolyte analytes in numerous pools of lyophilized quality control sera is evaluated. Using data obtained between 1973 and 1976 from Regional Quality Control Programs utilizing the Quality Assurance Service of the College of American Pathologists, monthly group mean values are studied as a function of time, by means of linear regression analysis. In the 28 pools studied, unstable analyte-pool combinations were detected in approximately 35% of the cases. Total protein was the most universally stable. In a large percentage of pools, minimally increasing concentrations of sodium, chloride, and potassium were found, while inorganic phosphorus decreased in the majority of pools. In pools with changing enzymatic activiteis, alkaline phosphatase tended to increase and creatine phosphokinase generally decreased. Changes in levels of calcium, serum glutamic oxaloacetic transaminase, and lactate dehydrogenase were inconsistent. Changes in analyte concentration were judged in relation to the precision (SD) with which the analytes were measured. The ratios of rate of change in analyte value to SD were lower for electrolytes than for other analytes.

Alkaline Phosphatase↗
PubMed1994

[Quality control of cytologic diagnosis].

To assure the quality of cytologic diagnosis, the most important process is review of the previous cytologic and histologic examinations. Correlations of cytologic-histologic diagnosis should be reconfirmed. If diagnostic inconsistency is found, the cause must be explained. Now the computer system combining cytologic and histologic records is indispensable for quality control of cytologic diagnosis.

Clinical Laboratory Information Systems↗
PubMedDate not supplied

Implementation and evaluation of a national external quality control program for cervical cytology in Mexico.

OBJECTIVE: To evaluate cytology laboratories and the performance of cytotechnologists for establishing efficient external quality control for Mexico's National Program for the Prevention and Control of Cervical Cancer. MATERIAL AND METHODS: During January and February 1998, an onsite evaluation of all cytology laboratories of the Ministry of Health found that only 70% of the microscopes were in adequate working conditions, reagents were out of date, and working conditions were sub-optimal. A program for external quality control based on proficiency testing was established for cytotechnologists. Fifty slide sets with 20 Papanicolaou slides and 10 photographic slides were prepared. The sets were given to the cytotechnologists for evaluation and again one year later by courier. RESULTS: Twenty-one percent of microscopes were repaired and 9% replaced; reagents were distributed and laboratory facilities improved. Only 16% of cytotechnologists passed the initial proficiency test. Cytotechnologists received a refresher training course: one year later 67% of them passed the proficiency test. To ascertain that each slide was correctly diagnosed, 41 sets were rescreened by expert cytopathologists or cytologists and their diagnoses compared to the original ones. Thirty-seven sets had 86% to 96% concordance. CONCLUSIONS: This new system for external quality control of cervical cytology allowed the opportune and reliable evaluation of the performance of cytotechnologists.

Diagnostic Errors↗
PubMed1993

[Problems of survey materials in external quality control survey].

In the past over twenty years the Japan Medical Association Quality Control Survey Committee has experienced various types of problems in preparing a large amount of different control survey materials with some matrix effects. This may have caused inappropriate evaluation for some of the participated laboratory. Not only the participated laboratories but also some industrial companies should participate to identify the exact matrix effects, so that the Committee may be able to avoid some inappropriate decisions on evaluation of the reported results. However, at the present time, no standard is available for the identification of matrix effects. The Japanese Committee for Clinical Laboratory Standards, in 1991, organized the research group on external quality control, and suggested a proposal to identify some matrix effects of survey materials for a particular assay system.

Data Collection↗