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PubMed1999

Activity of gatifloxacin against Haemophilus influenzae and Moraxella catarrhalis, including susceptibility test development, E-test comparisons, and quality control guidelines for H. influenzae.

In vitro antimicrobial activity and susceptibility testing interpretation criteria and quality control were studied for gatifloxacin, a new 8-methoxy fluoroquinolone, tested against Haemophilus influenzae. Moraxella catarrhalis (600 strains) and H. influenzae (1,400 strains) from the SENTRY Antimicrobial Surveillance Program in North America (Canada and the United States) were also tested against gatifloxacin and 12 other antimicrobial agents. Gatifloxacin (MIC at which 90% of the isolates are inhibited [MIC90], </=0.03 microg/ml; 100.0% of strains inhibited at </=2 microg/ml) was the most active agent tested against H. influenzae and was similar to four comparison fluoroquinolones (MICs, </=0.03 to 2 microg/ml) against M. catarrhalis. A subset of 300 recent clinical isolates of H. influenzae were tested by using media (Haemophilus Test Medium agar and broth) and procedures recommended by the National Committee for Clinical Laboratory Standards (NCCLS) and with the E-test (AB BIODISK, Solna, Sweden). Gatifloxacin (MIC50, 0.008 microg/ml) was slightly more active than levofloxacin, and E-test results were generally elevated by 0.5 log2 dilution step compared to reference MICs. The gatifloxacin 5-microg disk test produced zone diameters that were routinely above 30 mm for H. influenzae strains, corresponding to gatifloxacin MICs of 0.008 or 0. 016 microg/ml. The gatifloxacin susceptibility breakpoint proposed for nonfastidious species (</=2 microg/ml; >/=18 mm) was also suggested for H. influenzae testing. No interpretive errors were observed. Quality control guidelines for H. influenzae ATCC 49247 were determined by using the NCCLS M23-T3 (1998) study design. The results from the nine-laboratory protocol suggested the following control ranges: for broth microdilution tests, 0.004 to 0.03 microg/ml; for disk diffusion testing, 33 to 41 mm. Gatifloxacin appears to be a potent anti-Haemophilus fluoroquinolone compound with in vitro testing interpretive criteria that will produce accurate results (disk diffusion, broth microdilution, and E-test).

Anti-Bacterial Agents↗

PubMed2004

The ER glycoprotein quality control system.

The endoplasmic reticulum (ER) is the major site for folding and sorting of newly synthesized secretory cargo proteins. One central regulator of this process is the quality control machinery, which retains and ultimately disposes of misfolded secretory proteins before they can exit the ER. The ER quality control process is highly effective and mutations in cargo molecules are linked to a variety of diseases. In mammalian cells, a large number of secretory proteins, whether membrane bound or soluble, are asparagine (N)-glycosylated. Recent attention has focused on a sugar transferase, UDP-Glucose: glycoprotein glucosyl transferase (UGGT), which is now recognized as a constituent of the ER quality control machinery. UGGT is capable of sensing the folding state of glycoproteins and attaches a single glucose residue to the Man9GlcNAc2 glycan of incompletely folded or misfolded glycoproteins. This enables misfolded glycoproteins to rebind calnexin and reenter productive folding cycles. Prolonging the time of glucose addition on misfolded glycoproteins ultimately results in either the proper folding of the glycoprotein or its presentation to an ER associated degradation machinery.

Amino Acid Sequence↗

PubMed2006

Quality control in tissue banking--ensuring the safety of allograft tissues.

DESPITE FEDERAL REGULATIONS for tissue-banking practices, inadequate quality control led to the largest allograft tissue recall in history in October 2005. THE RECALL INCLUDED all allograft tissues obtained from 761 donors and distributed by five tissue banks. Many of these tissues already had been implanted and were unrecoverable. THIS ARTICLE DESCRIBES the many tissue-banking industry variables, including donor selection and testing and tissue recovery, processing, and preservation. QUESTIONS THAT HEALTH CARE providers can ask to determine which tissue banks' quality control measures best ensure the safety of the allografts they provide also are included.

Communicable Disease Control↗

PubMed1986

Statistical quality control methods in standardization of BCG vaccines.

The quality control of the BCG vaccine lacks the requirements of exact statistical methods, although the principles of bioassay have been required in the control of other biological products for a long time. For a remedy and to eliminate controversies in the interpretation of the laboratory results of BCG products valid statistical control is needed. In the four major laboratory test systems generally used to control: the viability of the BCG products, the residual virulence of the BCG strains, the allergenic potency and 4) the immunogenic potency of the BCG vaccines the following statistical methods should be required: estimations of the unbiased point and 95% confidence interval of the viable units 10(6)/ml, the mean residual virulence, the mean allergizing and protective capacity in appropriate models, the expressions of the relative potency of the in vitro viability and the in vivo test systems to a Reference Preparation, hypothesis tests using the unbiased estimates for the comparison of the estimated parameters of the controlled vaccines (Anova) and testing the stability of the viability (Regranal), multiple comparison with the ranked estimates to diminish Type I error in rejected null hypotheses, test of concordance between the sets of ranked parameters of the different test systems. Valid models will promote the standardization of the BCG vaccine, will ensure the objective statistical inference of the control results, the interpretation of the immunogenicity and reactogenicity of the BCG vaccines and the understanding of the epidemiological processes in tuberculosis.

Animals↗

PubMed1993

External quality control performance in clinical chemistry: experience in Kenya.

Analysis of eleven biochemical laboratory tests was done during an International External Quality Assessment Scheme (IEQAS) in which the clinical chemistry laboratory at Kenyatta National Hospital participated. Technicon SMA II continuous flow system was used in the biochemical analyses apart from glucose which was assayed manually by the glucose oxidase method. Using the standard deviation index (SDI), twenty six percent of the results were found to be outside the two standard deviation (2SD) limit. However, when variance index score (VIS) was used, 42% of the results were found to be outliers. Overall, our laboratory performed poorly compared to other laboratories in both the IEQAS and the United Kingdom External Quality Assurance Scheme (UKEQAS). This poor performance is attributed to the use of improper equipment which is not regularly maintained, lack of diagnostic reagents, lack of quality control (QC) materials and inadequate staff training in the field of quality control.

Animals↗

PubMed1982

[Use of the ROC method in problems of image quality and quality control in mammography].

The ROC method is being used increasingly in radiology for the purpose of checking image quality. A phantom has been developed for use in mammography, which takes account of the tissues of the breast and of abnormal changes. In order to compare image quality, various films and film-screen systems were employed. The effect of slice-thickness, focal spot size and radiation scatter on image quality has been examined. The suitability of the method for quality control has been tested on a small sample. In addition, certain important parameters of the radiographic technique have been determined by physical measurements. Certain methodological difficulties must be considered, eg. the problem of statistical significance. It has been shown, however, that film-screen systems can approach the image quality of screenless films and require a lower dose of x-rays. For larger slice thickness, the use of a grid produces significantly better results than film without screens alone. The findings of the quality control show that it is important to check image quality by means of physical measurements. The ROC method has proved less valuable in this respect.

Female↗

PubMed1993

A European Quality Control Programme as a cooperative tool between users and a diagnostic company.

Achievement of appropriate precision is a major challenge for the clinical laboratory, particularly in specialized fields such as enzymology and immunochemistry. Especially in immunochemistry, where accuracy can only poorly be checked because of a lack of reference methods and a multitude of detectable epitopes, precision remains an important index of quality. In immunochemical methods there are three main sources of variation: differences in methodology, lot-to-lot variation and performance of the assay, the latter including the skill of the technicians and instrument performance. The results of a European Quality Control Programme for the users of one type of automated immunoassay analyser were compared with a similar Italian Quality Control Programme for users of different immunometric techniques. The precisions (%CV) of the two programmes were compared, as well as the number of values lying within one half of the biological variation of the analysed serum components. Feedback between users and manufacturers leads to a clear improvement in analysis performance, so that most of the considered values come to lie within the acceptable limits of 1/2 of the biological variation. It is concluded that both national and international quality control programmes are very useful for indicating the intrinsic quality of the quantities used in the clinical laboratory.

Biomarkers, Tumor↗

PubMed1997

Quality control aspects of the Philips multileaf collimator.

BACKGROUND AND PURPOSE: Linear accelerators equipped with multileaf collimators (MLCs) are becoming more common and are widely available from most commercial manufacturers. There is a need to ensure they retain their commissioning specification using a preventative maintenance and quality control (QC) programme. This paper considers the design criteria of the Philips MLC which are important to the production of a comprehensive quality control programme. MATERIALS AND METHODS: The specific QC problems related to MLCs are identified as the positional accuracy of the leaves and their relationship to the back-up collimators, leakage considerations, the relationship of X-ray to light field and the influence of gravity on the positioning and leakage characteristics of the leaves. These problems are considered in relation to the general design considerations of the MLC, and methods of performing routine quality control checks are discussed. RESULTS AND CONCLUSIONS: The introduction of MLCs into clinical use results in new QC procedures being developed but it can be concluded that for the Philips MLC only an extra 30 min of QC time is needed per month and that its use has added little to the general down-time of this department.

Calibration↗

PubMed1981

A low-contrast phantom for daily quality control.

A simple phantom is proposed to provide a low-contrast test object for daily quality assurance. The phantom consists of four quarters and five dimes taped to a Plexiglas plate. For daily quality control, the phantom is used with 5 cm of Plexiglas as scattering material and a flood source. Examples of images are presented for several gamma cameras, illustrating some of the information that can be obtained. In particular, we present examples of cameras providing improper imaging performance with the coin phantom but with "normal" floods and bar-phantom images. The major conclusion is that daily quality-control images should include significant of scattering material and low-contrast objects.

Models, Structural↗

PubMed1983

Calibration and quality control of spirometer systems.

Spirometry is widely performed by a variety of health professionals in settings outside the traditional pulmonary function laboratory. It is important to very that test results are accurate, because they are used to establish diagnoses and guide therapy. A quality-control program will help verify the accuracy of testing procedures and must be developed based on equipment, personnel, and test application. Calibration is part of quality control and its meaning has evolved to include limited performance-testing. Large syringes and recently available flow calibrators allow determination of spirometer accuracy and make calibration rapid and convenient. They have the additional advantage of being portable and thus can accompany the spirometer on field trips. Calibration techniques may help in other aspects of quality control, such as test methodology and monitoring technician proficiency. Technicians are often evaluated on the ability to prepare, calibrate, and troubleshoot equipment, gain patient cooperation, determine the adequacy of effort, and calculate spirometry results. Calibration techniques may help in many aspects of this evaluation. Finally, advanced techniques may be used to study the methods used in performing clinical spirometry.

Calibration↗

PubMed1994

Quality control of "one touch" II blood glucose meters used by nurses in clinical departments.

Most analyses of blood glucose concentrations in our hospital are performed bedside by nurses with One Touch II blood glucose meters. The laboratory is responsible for the test results and therefore a quality control system which includes the performance by the nurses, is necessary. Human serum, spiked sterilised horse blood and (spiked) human blood were tested with 39 One Touch II blood glucose meters for usefulness in extra-laboratory quality control schemes. Serum gave high imprecision (CV > 9%) and leaked through the strips, contaminating the meters. Horse blood gave unacceptable imprecision (CV = 6.7%) and human blood could not be used due to an unpredictable time course of the glucose values in the distributed samples. Addition of NaF increased the CV of the measurements by more than 2%. Only the One Touch control solutions (3 levels) resulted in satisfactory precision (CV = ca. 4%) and are therefore suitable for extra-laboratory quality control of precision. However, accuracy control has to be done within the laboratory with fresh human blood.

Animals↗

PubMed1983

Quality-control sera for routine determination of aluminum by electrothermal atomic absorption spectroscopy.

Several commercially available quality-control sera were analyzed for aluminum content by atomic absorption spectroscopy with a stabilized-temperature graphite furnace. The values obtained ranged between 4 and 1250 micrograms/L (0.148 to 46.235 mumol/L). No significant difference was detected for between-vial variation for four lots of quality-control sera (p greater than 0.05). Control sera stored in 1-mL polypropylene vials and frozen at -20 degrees C for up to six months showed no significant variation in aluminum content (p greater than 0.05), but those stored in their original glass containers had significantly increased aluminum content (p less than 0.001) over a four-week period.

Aluminum↗

PubMed2006

[Quality control of prenatal ultrasound. A role for biometry].

Because of an increasing demand for limited health care resources as well as an increasing impact of legal aspects in ultrasound practice, it has become necessary to ensure that screening procedures are cost-effective and clinically effective and to develop systems that could help sonographists in certifying their practice. Based on the literature, various approaches for quality control are reviewed. Special emphasis is put on the use of fetal biometry and statistical tools to develop quality control systems based on both qualitative and quantitative approach. Besides their potentials for audit and quality control, such tools could also be useful during the process of training.

Biometry↗

PubMed1985

Quality control of automated cellular analyses -- the fallibility of embalmed blood.

The use of preserved blood for quality control is well established. The treatment of such materials to extend their life can impart a property to those materials such that external contaminants to diluents used for subsequent analysis may not be detected by these materials and give a false sense of security in a quality control program. The effect of the contaminant on fresh cells is more of a problem. Most contaminants affect cell volume, particularly the red cells which have been studied in-depth. White cell differential screening by size analysis is similarly affected. The recognition of the different properties of fresh and preserved blood helps explain results.

Blood Cell Count↗

PubMed2004

Inter-laboratory quality control for hormone-dependent gene expression in human breast tumors using real-time reverse transcription-polymerase chain reaction.

Quantitative reverse transcription-polymerase chain reaction (RT-PCR) used to detect minor changes in specific mRNA concentrations may be associated with poor reproducibility. Stringent quality control is therefore essential at each step of the protocol, including the PCR procedure. We performed inter-laboratory quality control of quantitative PCR between two independent laboratories, using in-house RT-PCR assays on a series of hormone-related target genes in a retrospective consecutive series of 79 breast tumors. Total RNA was reverse transcribed in a single center. Calibration curves were performed for five target genes (estrogen receptor (ER)alpha, ERbeta, progesterone receptor (PR), CYP19 (aromatase) and Ki 67) and for two reference genes (human acidic ribosomal phosphoprotein PO (RPLPO) and TATA box-binding protein (TBP)). Amplification efficiencies of the calibrator were determined for each run and used to calculate mRNA expression. Correlation coefficients were evaluated for each target and each reference gene. A good correlation was observed for all target and reference genes in both centers using their own protocols and kits (P < 0.0001). The correlation coefficients ranged from 0.90 to 0.98 for the various target genes in the two centers. A good correlation was observed between the level of expression of the ERalpha and the PR transcripts (P < 0.001). A weak inverse correlation was observed in both centers between ERalpha and ERbeta levels, but only when TBP was the reference gene. No other correlation was observed with other parameters. Real-time PCR assays allow convenient quantification of target mRNA transcripts and quantification of target-derived nucleic acids in clinical specimens. This study addresses the importance of inter-laboratory quality controls for the use of a panel of real-time PCR assays devoted to clinical samples and protocols and to ensure their appropriate accuracy. This can also facilitate exchanges and multicenter comparison of data.

Aromatase↗

PubMed2003

Cytotoxic activity and quality control determinations on Chelidonium majus.

The quality control determinations on herba and radix Chelidonii prepared from Chelidonium majus L., growing wildly in Bursa, Uludağ surroundings, have been conducted according to DAB 9. Ash, humidity and total alkaloidal content have been carried out. LC(50) value of chelidonine and protopine, the most important alkaloids, and the alcoholic and water extracts of herba Chelidonii were determined using brine shrimp (Artemia salina) lethality bioassay.

Alkaloids↗

PubMed2002

Quality control of sampling: proof of concept.

Quality control in sampling has been demonstrated as practicable in sampling procedures that require the combination of sample increments to form a composite sample. The proposed method requires no sampling resources or use of time beyond those normally used. Increments are allocated at random into two half-sized composites, each of which is analysed separately. The absolute difference between the two results is plotted on a one-sided control chart, which is interpreted like a Shewhart chart. In commonly prevailing circumstances the analytical precision is negligible and the chart represents sampling precision alone.

Journal Article↗

PubMed2005

Energetics of substrate binding and catalysis by class 1 (glycosylhydrolase family 47) alpha-mannosidases involved in N-glycan processing and endoplasmic reticulum quality control.

Nascent glycoproteins are subject to quality control in the lumen of the endoplasmic reticulum (ER) where they can either be effectively folded with the aid of a collection of ER chaperones or they can be targeted for disposal in a process known as ER-associated degradation. Initiation of the ER disposal process involves selective trimming of N-glycans by ER alpha-mannosidase I and subsequent recognition by the ER degradation-enhancing alpha-mannosidase-like protein family of lectins, both members of glycosylhydrolase family 47. The kinetics and energetics of substrate binding and catalysis by members of this family were investigated here by the analysis of wild type and mutant forms of human ER alpha-mannosidase I. The contributions of several amino acid residues and an enzyme-associated Ca(2+) ion to substrate binding and catalysis were demonstrated by a combination of surface plasmon resonance and enzyme kinetic analyses. One mutant, E330Q, shown previously to alter general acid function within the catalytic site, resulted in an enzyme that possessed increased glycan binding affinity but compromised glycan hydrolysis. This mutant protein was used in a series of glycan binding studies with a library of mannose-containing ligands to examine the energetics of Man(9)GlcNAc(2) substrate interactions. These studies provide a framework for understanding the nature of the unusual substrate interactions within the family 47 mannosidases involved in glycan maturation and ER-associated glycoprotein degradation.

Calcium↗