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PubMed1977

Evaluation of ampouled tonometered buffer solutions as a quality-control system for pH, pCO2, and pO2 measurement.

In response to the need for an adequate quality-control system for blood-pH and blood-gas analyzers, we investigated the practical application of ampouled phosphate-bicarbonate-chloride solutions tonometered with mixtures of carbon dioxide, oxygen, and nitrogen. This system offers three discrete sets of pH, pCO2, AND PO2 values, which are consistent with normal and pathophysiologically high and low values. The stated values were based on the U.S. National Bureau of Standards scale for pH and on gas analysis for pCO2 and pO2. Influence of temperature, air contact, calibration gas, and storage was established. Internal and external quality control by means of these ampoules is presented. The system is stable, accurate, precise, and suitable for simultaneous quality control of pH, pCO2, and pO2 measurements.

Bicarbonates↗
PubMed1999

Standardisation of DNA quantitation by image analysis: quality control of instrumentation.

BACKGROUND: DNA image analysis is frequently performed in clinical practice as a prognostic tool and to improve diagnosis. The precision of prognosis and diagnosis depends on the accuracy of analysis and particularly on the quality of image analysis systems. It has been reported that image analysis systems used for DNA quantification differ widely in their characteristics (Thunissen et al.: Cytometry 27: 21-25, 1997). This induces inter-laboratory variations when the same sample is analysed in different laboratories. In microscopic image analysis, the principal instrumentation errors arise from the optical and electronic parts of systems. They bring about problems of instability, non-linearity, and shading and glare phenomena. METHODS: The aim of this study is to establish tools and standardised quality control procedures for microscopic image analysis systems. Specific reference standard slides have been developed to control instability, non-linearity, shading and glare phenomena and segmentation efficiency. RESULTS: Some systems have been controlled with these tools and these quality control procedures. Interpretation criteria and accuracy limits of these quality control procedures are proposed according to the conclusions of a European project called PRESS project (Prototype Reference Standard Slide). Beyond these limits, tested image analysis systems are not qualified to realise precise DNA analysis. CONCLUSIONS: The different procedures presented in this work determine if an image analysis system is qualified to deliver sufficiently precise DNA measurements for cancer case analysis. If the controlled systems are beyond the defined limits, some recommendations are given to find a solution to the problem.

DNA, Neoplasm↗
PubMed1983

Reproducibility and quality control in the analysis of biological samples for lead and mercury.

A simple statistical calculation was applied to 8 years of data on routine control sample and duplicate analyses from a laboratory quality control program. This provided standard deviations truly representative of this laboratory at no additional analytical expense, and accurate information on how they varied with concentrations. From these, the detection limit of the method, upper warning limits, and upper control limits for differences between duplicate analyses were calculated. These values were conveniently used for quality control in determinations of lead in blood and of mercury in urine.

Computers↗
PubMed1999

Business quality control in issuing life insurance.

Fraud investigation and fraud control are entirely different processes. Similarly the auditing of a life insurance company and the issuing of life insurance policies and business quality control are not the same. Business quality control and fraud control have much in common. In this article, these similarities are explored and a case is made that companies issuing life insurance policies should consider the business quality control approach rather than the more traditional investigatory methods.

Commerce↗
PubMed1989

Quality control procedures for monitoring whole blood and plasma trace metal levels by atomic absorption spectrophotometry.

Well co-ordinated quality control procedures are required to insure that trace metal results determined at ppb (micrograms kg-1 or micrograms l-1) levels by atomic absorption spectrophotometry are reliable. Control materials can be prepared "in-house" provided they are calibrated against standard reference materials (SRM). A mean +/- SD data base should be determined for each quality control material with daily results plotted on Levey-Jennings charts. Westgard's multi-rule quality control scheme is recommended for assessing analytical performance. Additional information may be obtained by using cumulative sum (cusum) charts to detect analytical drift from the mean, and standard deviation index or 'z-score' plot to show analytical bias. Proficiency or quality assurance programs should be used to supplement internal quality verification of analytical performance.

Humans↗
PubMed1984

A computer program for quality control in the blood gas laboratory.

In blood gas laboratory quality-assurance programs, which are routinely included with materials sold for quality control, raw data are sent to a data processing center for reduction to statistics meaningful to the laboratory's quality-control effort. This data reduction service usually requires a turn-around time of 2 weeks or more. I describe a computer program for the more timely, in-house computation of a laboratory's mean, standard deviation, and coefficient of variation. We have also found this program useful in calculating values for a new lot number of controls during the period between receipt of the controls and receipt of the first set of statistics from the data processing center. Comparing these values to the assayed values in the manufacturer's insert provides timely feedback and augments the manufacturer's professional data reduction service.

Blood Gas Analysis↗
PubMed1992

Inaccuracy quality control in the monitoring of trace metal concentrations in biological fluids.

Quality assurance in trace element analysis requires continual surveillance of the accuracy and precision of results. A review of difficulties encountered in performing quality control programs of trace metal analysis in biological fluids is presented. Examples to clarify the inadequacy of available biological reference materials for quality control in biological monitoring of environmental and occupational low level exposure to metals are reported.

Body Fluids↗
PubMed1995

A linear modelling approach to automatic interpretation of quality control measurements in mammography.

An approach to the automated interpretation of quality control data is described in which the relationship between small changes in system performance and the resulting small changes in the measured quality control test results are approximated as a set of linear equations in matrix form. The inverse of this forward matrix is then used to identify causal changes from the set of measured changes. This approach has been investigated for the case of mammographic screening quality assurance and shown to provide a potentially useful tool to assist in the interpretation task.

Autoanalysis↗
PubMed2006

Uncertainty-based internal quality control. Harmonization considerations.

Three main quality aspects for analytical laboratories are internal method validation, internal quality control (IQC), and sample result uncertainty. Unfortunately, in the past they have been used in a nonharmonized way. The most universal IQC tool is the mean chart, but some criteria used to fix their control limits do not fit the real nature of analytical results. A new approach for fixing these limits is proposed (the u-approach). The key is the combined uncertainty, u, obtained from the method validation information, also used for estimating the sample result uncertainty. A comparative study on "in-control" simulated, bibliographic, and real laboratory data suggests that the u-approach is more reliable than other well-established criteria. In addition, the u-approach mean chart emerges as an IQC tool, consistent with chemical assays, which harmonizes the validation-control-uncertainty process.

Journal Article↗
PubMed1989

Standardization of disk diffusion and agar dilution susceptibility tests for Neisseria gonorrhoeae: interpretive criteria and quality control guidelines for ceftriaxone, penicillin, spectinomycin, and tetracycline.

A six-laboratory study developed a standardized method for determining the susceptibilities of Neisseria gonorrhoeae strains to penicillin, tetracycline, spectinomycin, and ceftriaxone. Three quality control organisms were also selected, and quality assurance guidelines were initially generated for the disk diffusion and agar dilution methods. The medium recommended for gonococcal susceptibility testing was GC agar with a defined "XV-like" supplement. The supplement should be free of cysteine, a component implicated in the inactivation of some newer beta-lactam compounds. Penicillin, tetracycline, spectinomycin, and ceftriaxone were stable in agar plates stored at 3 to 5 degrees C for at least 2 weeks. Numerous GC agar and drug disk lots were used during the trials without significant variation in test results. Several other gonococcal strains were recommended for additional medium quality assurance. The disk quality control zone limits were established for N. gonorrhoeae ATCC 49226 (formerly CDC F-18) and Staphylococcus aureus ATCC 25923. MIC quality control ranges were also developed for N. gonorrhoeae ATCC 49226 and S. aureus ATCC 29213. The interpretive criteria for penicillin were as follows: susceptibility, greater than or equal to 47 mm (diameter of inhibition zone) (less than or equal to 0.06 micrograms/ml [MIC]); resistance, less than or equal to 26 mm (greater than or equal to 2 micrograms/ml). For tetracycline they were as follows: susceptibility, greater than or equal to 38 mm (less than or equal to 0.25 microgram/ml); resistance, less than or equal to 30 mm (greater than or equal to 2 micrograms/ml). For spectinomycin they were as follows: susceptibility, >/= 18 mm (</= 32 micrograms/ml); resistance, </= 14 mm (>/= 128 micrograms/ml). For ceftriaxone susceptibility, the criterion was >/= 35 mm (</= 0.25 micrograms/ml) with no other category. Criteria of </= 19 mm for plasmid-mediated resistances to penicillin and tetracycline were also confirmed. The false-susceptibility errors were </= 1% with these criteria.

Ceftriaxone↗
PubMed1979

[Quality control on antibiotic sensitivity tests: preliminary trials (author's transl)].

A quality control study in clinical microbiology was instituted by A.M.O.I. (Associazione Microbiologi Ospedalieri Italiani) since 1974. Preliminary results are reported on sensitivity tests quality control made by a group of laboratories in various parts of Italy. Our data show the great variety of methods used for antibiotic sensitivity disk determination and therefore the opportunity to standardize this procedure.

Italy↗
PubMed1985

Quality control log with CUSUM and clinically useful limits criteria.

We describe a quality control (QC) log including its advantages over the more commonly used Levey-Jennings and Shewart graphic charts. It represents a practical system of analytic quality control for quantitative assays in clinical chemistry. It utilizes cumulative sum (CUSUM) techniques and comparison of means to monitor acute and chronic analytic drift, respectively. Clinically useful limits (CUL) criteria for QC decisions are used. An algorithm to facilitate the description of, training for, and use of, the QC log system is provided.

Chemistry, Clinical↗
PubMedDate not supplied

[Check of compliance with quality criteria for diagnostic radiographic images in quality control].

PURPOSE: To devise and implement a programme of measurements to assess the entrance surface dose for a standard-sized patient and to check the compliance with diagnostic reference levels. MATERIAL AND METHODS: Dose evaluation was performed on 40 radiographic instruments. The exposure parameters were collected for the main radiographic procedures (chest, skull, spine, pelvis, abdomen) each performed with instrument on a standard-sized patient. The output of each X-ray tube at 70, 80, 90, 100, 110 and 120 kV was measured with a solid state detector during quality controls. Beam quality and geometric characteristics of the equipment were also determined. The entrance surface dose for a standard patient was assessed for each procedure carried out with the 40 instruments, thus obtaining a total of 155 radiographic techniques. Finally, the method was validated by comparing the values obtained with the solid state and an ionization chamber for X-ray beam detector. RESULTS: The comparison between the solid state detector and the ionisation chamber demonstrated a good agreement. Results show that reference diagnostic levels are respected in most examinations (147/155) even if exposure values do not always comply with those indicated by European guidelines. The measurement programme seems to be applicable in hospital practice where the large number of radiographics instruments and procedures requires the acquisition and processing of a large number of data. CONCLUSIONS: The evaluation of patient dose during quality control is feasible and allows a first check of compliance with reference levels in order to identify which procedures can be optimised by means of more specific measurements and assessments.

Guideline Adherence↗
PubMed1978

[Reflections on quality control in perinatalogy exemplified by the Munich Perinatal Study (author's transl)].

Quality control has four component parts: standardized observation, a procedure to measure the quality of individual production, a technique for aggregating and comparing measurements, and a means by which the behaviour of the subjects can be influenced by these comparisons. The greatest problems, which often remain unsolved, can be traced to the definition and measurement of the quality of medical care. Some problems and the feasibility of quality control are demonstrated using perinatalogy and the Munich Perinatal Study as models. This trial of self control shows that voluntary participation of the hospitals, assured anonymity, self-responsibility, and a statistical evaluation that can be used for educational purposes play an important part.

Female↗
PubMed2003

[The protein quality control and neurodegeneration].

There are growing lines of evidence addressing a potential link between failure of protein quality control and neurodegeneration. Hence, it is important to know the quality control mechanism of the cell for understanding the molecular basis underlying neurodegenerative diseases. To date, it is notable that molecular chaperones and the ubiquitin-proteasome system play a central role for maintenance of protein homeostasis by catalyzing refolding and/or the immediate destruction of misfolded or impaired proteins generated in cells. However, how this proteolytic machinery recognizes abnormality of cellular proteins for selective elimination remains largely elusive. In this article, we discuss the mechanism of neurodegeneration, based on the protein quality control mediated by the ubiquitin-proteasome system in the cell.

Cysteine Endopeptidases↗
PubMed2005

Endoplasmic reticulum-associated protein quality control and degradation: screen for ERAD mutants after ethylmethane sulfonate mutagenesis.

Proteins destined for secretion in eukaryotic cells enter the endoplasmic reticulum (ER) in an unfolded state and are properly folded in this organelle and sent to their final destination. Misfolded or orphan proteins are retained in the ER by a quality control system, retrotranslocated into the cytosol and degraded. Soluble and membrane proteins were found to require a basic machinery for elimination. It is composed of (1) the E1 (ubiquitin activating), E2 (ubiquitin conjugating), and E3 (ubiquitin ligase) enzymes, which polyubiquitinate the substrate proteins during retrotranslocation; (2) the trimeric AAA-ATPase complex Cdc48-Ufd1-Npl4p, which liberates the polyubiquitinated proteins from the ER; and (3) the 26S proteasome, finally degrading the misfolded proteins. Additional components for degradation of soluble or membrane proteins may vary depending on the nature of malfolded proteins. It is therefore of utmost importance to gain insight into the different components of the ER protein quality control and degradation system required for the elimination of the substrate variety. Protein quality control of the ER and subsequent degradation are evolutionarily highly conserved from yeast to human. The yeast Saccharomyces cerevisiae is therefore an elegant model organism for a search of new components of the ER quality control and degradation machinery, because it is easily amenable to genetic and molecular biological experimentation. In this chapter, a genetic approach is presented, which leads to the isolation of mutants and to the identification of proteins involved in protein quality control and ER-associated degradation (ERAD). The method resides in ethylmethane sulfonate (EMS) mutagenesis of a yeast strain followed by screening for stabilization of soluble ERAD substrates, two mutated and consequently malfolded vacuolar enzymes, carboxypeptidase yscY (CPY*) and proteinase yscA (PrA*). Both malfolded proteins are retained in the ER lumen and become substrates of the ERAD machinery.

Endoplasmic Reticulum↗
PubMed1992

Auditing quality control procedures in a chemical pathology laboratory--a multiple regression analysis.

We undertook a retrospective analysis of the monthly test rejection rates and the monthly external quality assessment scheme performance indices for our laboratory's two automated analysers, and examined the association of these variables with measures of laboratory workload, manpower, staff training, instrument servicing, seasonal and temporal factors and changes of calibration, method and assigned internal quality control values. Using multiple linear regression and stepwise multiple linear regression, we found that test rejection rates differed significantly between instruments, and were highest on the instrument performing the widest variety and lowest volume of tests. On that instrument, rejection rates were significantly associated with the introduction of new staff and laboratory manpower levels, and also showed a highly significant trend upwards over the study period, independent of the effects of the other variables examined. External quality assessment scheme performance indices showed small trends over the study period. They were not related to the test rejection rates on either analyser but also showed a significant association with the introduction of new staff and a small but significant association with laboratory workload. We conclude that the training and introduction of new staff and decreased laboratory manpower levels may significantly increase the level of test rejection, and adherence to appropriate quality control protocols effectively maintains the quality of the laboratory's results, but may not be completely successful in filtering out the effects of some assignable causes of variation in test results. It is suggested that clinical laboratories use the statistical approach adopted here to identify factors which may be adversely affecting quality performance and running costs and to provide evidence that quality control procedures are both cost- and quality-effective.

Clinical Laboratory Techniques↗
PubMed1999

Quality control of smear microscopy for acid-fast bacilli: the case for blinded re-reading.

SETTING: Quality control of sputum smear microscopy, which is essential for ensuring correct tuberculosis (TB) diagnosis, is often performed through the unblinded rereading of all positive slides and a sample of negative slides. OBJECTIVE: To assess misclassification error introduced by knowledge of prior results. METHODS: The Southern Vietnam Regional TB Laboratory prepared three gold-standard sets of 750 slides: an unblinded set, an unblinded set in which 13% of negative slides were replaced by weakly positive slides purposefully mislabelled as negative, and a blinded set. Six provincial technicians who normally perform district quality control each reread 125 slides from each set. RESULTS: In the three sets only one negative slide was misread as positive. In the unblinded set (referent), 2.9% (9/311) positive slides were misread as negative, compared with 18.7% (57/305) in the blinded set (prevalence ratio [PR] = 6.5; 95% confidence interval [CI] 3.3-12.8; P < 0.001), and 11.3% (33/293) in the unblinded set with mislabelled slides (PR = 3.9; 95%CI 1.9-8.0; P < 0.001). CONCLUSIONS: False-negative error was more common than false-positive error. Knowledge of prior reading influences re-reading. Blinded re-reading of systematically selected slides would appear preferable, although this method requires high levels of proficiency among quality control technicians.

False Negative Reactions↗