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PubMed2025

Evaluating Selective Quality Control in Mammalian Oogenesis: Evidence and Opportunities.

The formation and maintenance of the finite mammalian ovarian reserve are critical for fertility and species survival. Genetic and developmental studies have uncovered various mechanisms underlying oocyte development and maturation, revealing two curious features of the ovarian germline: (a) The establishment of the follicle reserve involves an initial massive overproduction of oocyte precursors, and (b) the total number of ovulated oocytes across an animal's fertile lifetime is a very small proportion of the initial ovarian reserve. Many have proposed that this indicates the existence of selective quality control to ensure gamete fitness. Here, we review the findings underlying the hypotheses for germline quality control during prepubertal development, homeostatic fertility, and reproductive aging. We evaluate whether the existing evidence base distinguishes the active selection of specific germ cell subsets from neutral dynamics. Throughout, we discuss strategies for applying statistical frameworks to evaluate selection in oogenesis and the implications of neutrality versus selection at various points in oocyte development.

Oogenesis↗
PubMed2006

Quality control system of the endoplasmic reticulum and related diseases.

The quality control (QC) system of the endoplasmic reticulum (ER) is an important monitoring mechanism in the protein maturation process, which ensures export of properly folded proteins from the ER. Incorrectly or incompletely folded proteins are retained in the ER for refolding or degradation by the ER-residing proteasome. The calnexin/calreticulin cycle and ER-associated degradation are the key elements in QC. These two mechanisms work together to allow incorrectly folded proteins have additional opportunities to achieve their native conformations. The QC dysfunction is involved in many diseases caused by mutant proteins, many of which are causes of neurodegenerative disorders. A better understanding of molecular regulation in the QC system will uncover the molecular pathogenic mechanisms of many diseases caused by protein misfolding and help discover novel strategies for preventing or treating these diseases.

Alzheimer Disease↗
PubMed1990

A new chemiluminescence immunoassay for triiodothyronine and thyroxine: evaluation using quality control sera assayed in an interlaboratory survey.

A recently developed chemiluminescence immunoassay system (LIA-mat) for triiodothyronine and thyroxine, set up by Byk-Sangtec Diagnostica (Dietzenbach, Germany), has been evaluated and compared with radioimmunoassays and with a chemiluminescence enhanced enzyme immunoassay (Amerlite), using control materials circulated in a national interlaboratory quality control, as well as patient sera. The LIA-mat assays are competitive methods which use coated monoclonal antibodies and triiodothyronine- or thyroxine-ABEI (aminobutylethylisoluminol) conjugate as tracers. The working range of LIA-mat T3 (computed from the within-assay precision profile) extended from 1.4 to 12.3 nmol/l; the between-assay precision was 8.1 - 19.3 CV%. Regression analysis of the LIA-mat T3 results (y) against the consensus means (x) of the participants in the national interlaboratory survey yielded: y = -0.14 + 1.05 x, r = 0.95. The working range of LIA-mat T4 extended from 33 to 515 nmol/l; the between-assay precision was 5.4 - 9.2 CV%. An excellent agreement was found between LIA-mat T4 results (y) and the consensus means (x) of the laboratories participating in the national interlaboratory survey (y = 3.79 + 1.02 x, r = 0.98).

Dose-Response Relationship, Drug↗
PubMed1999

In vivo dosimetry using diodes as a quality control tool--experience of 2 years and 2000 patients.

This paper reports the use of diodes as a quality control tool on more than 95% of patients undergoing megavoltage radiotherapy during the past 2 years. The paper describes a simple method for using the diodes, a number of possible pitfalls and a quality issue raised by the measurements. In general, the results have been reassuring with very few patients falling outside a +/- 5% action level.

Breast Neoplasms↗
PubMed2001

Evaluation of a quality control phantom for digital chest radiography.

RATIONALE AND OBJECTIVES: To examine the effectiveness and suitability of a quality control (QC) phantom for a routine QC program in digital radiography. MATERIALS AND METHODS: The chest phantom consists of copper and aluminum cutouts arranged to resemble the appearance of a chest. Performance of the digital radiography (DR) system is evaluated using high and low contrast resolution objects placed in the "heart," "lung," and "subdiaphragm" areas of the phantom. In addition, the signal levels from these areas were compared to similar areas from clinical chest radiographs. RESULTS: The test objects included within the phantom were effective in assessing image quality except within the subdiaphragm area, where most of the low contrast disks were visible. Spatial resolution for the DR systems evaluated with the phantom ranged from 2.6 lp/mm to 4 lp/mm, falling within the middle of the line pair range provided. The signal levels of the heart and diaphragm regions relative to the lung region of the phantom were significantly higher than in clinical chest radiographs (0.67 versus 0.21 and 0.28 versus 0.10 for the heart and diaphragm regions, respectively). The heart-to-diaphragm signal level ratio, however, was comparable to those in clinical radiographs. CONCLUSION: The findings suggest that the attenuation characteristics of the phantom are somewhat different from actual chests, but this did not appear to affect the post-processing used by the imaging systems and usefulness for QC of these systems. The qualitative and quantitative measurements on the phantom for different systems were similar, suggesting that a single phantom can be used to evaluate system performance in a routine QC program for a wide range of digital radiography systems. This makes the implementation of a uniform QC program easier for institutions with a mixture of different digital radiography systems.

Humans↗
PubMed2000

Export of the high affinity IgE receptor from the endoplasmic reticulum depends on a glycosylation-mediated quality control mechanism.

The high affinity IgE receptor (FcepsilonRI) is a multisubunit complex comprised of either alphagamma(2) or alphabetagamma(2) chains. The cotranslational assembly of the IgE-binding alpha-chain with a dimer of gamma-chains occurs in a highly controlled manner and is proposed to involve masking of a dilysine motif present at the cytoplasmic C terminus of the FcepsilonRI alpha-chain that targets localization of this subunit to the endoplasmic reticulum (ER). Here, we show that ER quality control modulates export from the ER of newly synthesized alphagamma(2) and alphabetagamma(2) receptors. We demonstrate that the presence of untrimmed N-linked core glycans (Glc(3)Man(9)GlcNAc(2)) on the FcepsilonRI alpha-chain activates the ER quality control mechanism to retain this subunit in the ER, despite the presence of gamma-chains. At the same time, the untrimmed, ER-localized alpha-chain exhibits IgE-binding activity, suggesting that FcepsilonRI alpha-chain folding occurs before constitutive glucose trimming. In additional experiments, we demonstrate that cell surface expression of an alpha-chain C-terminal truncation mutant is also dependent on glucose trimming, but not on gamma-chain coexpression. We suggest that glucosidase trimming of terminal glucose residues is a critical control step in the export of FcepsilonRIalpha from the ER. Finally, we show that the constitutive ER FcepsilonRI alpha-chain, expressed in the absence of the other FcepsilonRI subunits, associates with the ER lectin-like chaperone calnexin, but not the structurally similar ER chaperone calreticulin, presumably through interaction with monoglucosylated alpha-chain ER glycoforms.

Animals↗
PubMed1980

Experiences with a regional quality control scheme for salicylate and paracetamol over a period of two years.

The organisation of a regional quality control scheme for salicylate and paracetamol estimations in plasma is described. The results show considerable variation in both bias and precision between laboratories, with some overall improvement in performance during the second year of the scheme. No method can be singled out as producing better results than the others. The major factor seems to be the care with which the analyses are performed.

Acetaminophen↗
PubMed1999

[Quality control in bone densitometry].

Bone densitometry is a biological measurement which must comply to the usual rules of quality control. Calibration phantoms are available and must be regularly measured. Results may be interpreted by visual inspection or by estimating drift percentage. Different calculation methods have been proposed. A rigorous procedure is required when replacing densitometry devices. Simple and regular controls can assure the reliability of the technique.

Absorptiometry, Photon↗
PubMed1992

Charts of operational process specifications ("OPSpecs charts") for assessing the precision, accuracy, and quality control needed to satisfy proficiency testing performance criteria.

"Operational process specifications" have been derived from an analytical quality-planning model to assess the precision, accuracy, and quality control (QC) needed to satisfy Proficiency Testing (PT) criteria. These routine operating specifications are presented in the form of an "OPSpecs chart," which describes the operational limits for imprecision and inaccuracy when a desired level of quality assurance is provided by a specific QC procedure. OPSpecs charts can be used to compare the operational limits for different QC procedures and to select a QC procedure that is appropriate for the precision and accuracy of a specific measurement procedure. To select a QC procedure, one plots the inaccuracy and imprecision observed for a measurement procedure on the OPSpecs chart to define the current operating point, which is then compared with the operational limits of candidate QC procedures. Any QC procedure whose operational limits are greater than the measurement procedure's operating point will provide a known assurance, with the percent chance specified by the OPSpecs chart, that critical analytical errors will be detected. OPSpecs charts for a 10% PT criterion are presented to illustrate the selection of QC procedures for measurement procedures with different amounts of imprecision and inaccuracy. Normalized OPSpecs charts are presented to permit a more general assessment of the analytical performance required with commonly used QC procedures.

Chemistry, Clinical↗
PubMed2003

Quality control of liquid herbal drug preparations: ethanol content and test on methanol and 2-propanol.

In the quality control of liquid herbal drug preparations, i.e. tinctures and liquid extracts, the ethanol content is determined and the test on methanol and 2-propanol is performed. Capillary headspace GC/MS methods for both analyses were developed and fully validated. These specific, selective, accurate and precise methods are a fast and fully automated alternative for the laborious methods of the European Pharmacopoeia, since they need no or only simple sample preparation.

2-Propanol↗
PubMed2004

Assign 2.0: software for the analysis of Phred quality values for quality control of HLA sequencing-based typing.

As improvements to DNA sequencing technology have resulted in increasing the throughput of DNA sequencing, the bottleneck for high throughput DNA sequencing-based typing (SBT) has shifted to sequence analysis, genotyping and quality control (QC). Consistent high-quality DNA sequence is required in order to reduce manual verification and editing of sequence electropherograms. However, identifying systematic changes in quality is difficult to achieve without the aid of sophisticated sequence analysis programs dedicated to this purpose. We describe a computer software program called Assign 2.0, which integrates sequence QC analysis and genotyping in order to facilitate high-throughput SBT. Assign 2.0 performs an analysis of Phred quality values in order to produce quality scores for a sample and a sequencing run. This enables sample-to-sample and run-to-run QC monitoring and provides a mechanism for the comparison of sequence quality between various genes, various reagents and various protocols with the aim of improving the overall quality of DNA sequence data. This, in turn, will result in reducing sequence analysis as a bottleneck for high-throughput SBT.

Alleles↗
PubMed1997

A decision support system for microbiology quality control.

Manual review of antibiotic sensitivity testing results is an essential component of a microbiology laboratory's quality control process. Such review is tedious and prone to human error, however. An expert system is described that remembers which susceptibility patterns are considered typical or atypical by expert reviewers, then uses these to prescreen future isolates. It uses a similarity function to allow matching against this library when two patterns are close, but not identical. Use of this system allows more efficient and reliable review of the laboratory's antibiotic sensitivity testing results.

Decision Support Systems, Clinical↗
PubMed1985

Inter-laboratory quality control of estrogen and progesterone receptor assays in breast cancer tissue using lyophilised cytosols.

In 1981 a quality control (QC) program for estrogen and progesterone receptor assays was organized among six laboratories in Ontario, Canada. Twenty-three vials of lyophilised cytosol prepared from human breast tumor tissues were analysed by each laboratory over a two-year period. Samples of each batch of QC material were analysed at least twice: either in the same batch or on separate occasions. The present study demonstrates the stability of the QC material, defines the relative accuracy of the receptor assays, and provides estimates of within-batch and between-batch precision of the receptor assays.

Breast Neoplasms↗
PubMed2005

Analysis of shielding materials in a Compton spectrometer applied to x-ray tube quality control using Monte Carlo simulation.

A realistic characterisation of the primary beam is very important for the quality control of X-ray tubes. The most accurate technique to assess the actual photon spectrum is X-ray spectrometry. Some difficulties arising in the spectrum determination can be avoided using a Compton spectrometer. Simulation models are useful tools to know the effect of some operational parameters, such as collimation of primary beam, relative position of focus and detector, and the influence of shielding materials. A simulation model has been developed using the MCNP code, based on the Monte Carlo method, in order to reproduce a commercial Compton spectrometer. In this work, the model developed is applied to analyse the influence on measurements of shielding materials present in the spectrometer.

Computer Simulation↗
PubMed1994

Quality control of bone densitometry in a national health survey (NHANES III) using three mobile examination centers.

A quality control (QC) program for bone mineral measurements at the proximal femur by dual-energy x-ray absorptiometry (DXA) was designed for the osteoporosis component of the Third National Health and Nutrition Examination Survey (NHANES III). Major elements of the QC program are (1) a QC center for review of all scans, (2) setup procedures for and continuous monitoring of daily QC procedures, (3) reference standards for cross-calibration, (4) longitudinal studies for assessment of instrument stability, (5) monitoring of technologist performance, and (6) training. This report describes the results of the QC program of the first half of this 6 year study, which began in 1988. Measurements were performed on 7376 subjects in three mobile examination centers, which traveled to a new location about every 3 months, a total of 44 locations. A small percentage (3.5%) of all scans were rejected, mostly because of patient motion during scanning, but 33% of the remaining scans required reanalysis at the QC center to refine the location of the regions of interest. Precision in spine and hip phantoms was below 1% at all ROIs. In 535 subjects with duplicate scans, age 20-91 of both sexes, examined in a blinded review, precision for BMD at the femur neck ROI was 3.2% (CV) and 5.1% for Ward's triangle BMD. The central review improved scan quality, increased the number of usable scans, and reduced significantly the range of the mean percentage difference in the duplicate scans. Minor alterations in machine function were observed and corrected. QC results on phantoms were similar to those obtained with stationary instruments in dedicated laboratories. Retrospective analysis of the regression slopes from QC records did not show a need for correction of the data base, indicating that the instruments were stable during the course of the study.

Absorptiometry, Photon↗
PubMed2002

[The National Patient Registry as a tool for continuous production and quality control].

INTRODUCTION: In Denmark, the National Register of Patients has, by law since 1977, received discharge diagnoses, surgical codes, and, in recent years, also codes for specific medical treatments for all hospitalised patients. It is an important source of administrative data and for epidemiological research. This paper summarises the results of an evaluation of the register as a tool for assessing quality in gynaecological departments in Denmark. MATERIAL AND METHODS: We obtained data describing production and quality of abortions, ectopic pregnancies, hysterectomies, endometrial ablations, ovarian cysts, ovarian, cervical, and endometrial cancer, in vitro fertilisation, insemination, and urine incontinence. A search was also made for possible miscodings in order to evaluate the extent of such miscoding and to obtain more valid quality estimates. RESULTS: The validity and completeness of the diagnosis codes were generally poorer than that of the surgical codes, especially that of the newer medical treatment codes. We found a rather different clinical practice and quality at the 38 gynaecological departments studied. In order to reduce this stochastic noise, we analysed all small departments as a single unit. Generally, the quality was the same in both the larger and the smaller units. CONCLUSION: The register seems well suited for routine production and quality control.

Abortion, Induced↗
PubMed2005

The Italian quality control scheme for crossmatching procedures and HLA sera screening: the 2002 pilot study.

CONTEXT: The first national quality control (QC) program of histocompatibility serum testing was performed in Italy in 2002. OBJECTIVE: To monitor the performance of HLA typing laboratories while meeting the accreditation requirements of the European Federation for Immunogenetics (EFI), which require HLA typing laboratories to participate in external QC of their crossmatch and antibody analyses. DESIGN: The Turin Transplant Immunology Service was asked to organize a QC survey of 17 HLA typing laboratories in Italy. Each laboratory received 12 serum specimens and 6 blood samples and was required to perform 36 crossmatches and 12 serum antibody specificity determinations. SETTINGS: Data of participating centers were compared to establish whether EFI requirements were satisfied. RESULTS: In crossmatch analysis, the results of 32 of 36 crossmatches reached the 75% consensus target, with all the participating laboratories meeting the standards of the EFI. In antibody analysis, only 7 of 17 laboratories met the EFI standards. CONCLUSION: The first Italian QC program shows that the participating laboratories obtained consistent results in crossmatching, whereas the results were less satisfactory in the determination of serum antibody specificity, where consensus was reached only with monospecific sera and antibody-negative samples.

Blood Grouping and Crossmatching↗
PubMed2006

Appropriate range of quality control limit for wet deposition monitoring.

Precipitation chemistry programs in different regions of the world have different quality control limits for ion balance parameter IPD in wet deposition monitoring (R). The range of R values was calculated by assuming sample rainwater models in this paper. It was found that R was influenced by the inorganic ion types, total ion concentrations (IS) and the accuracy of the measurements (a(i)). R was defined and calculated as a function of a(i) and ion concentration C(i). R values of different types of wet deposition (including ocean type, continent type and combined oceanic and continental deposition) were different. There were also differences between the samples of the same type if the samples had different total ion concentrations. When IS>100 microeq/L, the ranges of R of ocean type deposition, continent type deposition and combined oceanic and continental deposition were 5 approximately 7%, 5 approximately 9% and 5 approximately 11%, respectively. When IS<50 microeq/L, if a(i) was 100%, the range of R was 33 approximately 71% because of the lower accuracy. It was also found that R of each criterion was in the range of R as calculated in this paper when IS>or=50 microeq/L, but when IS<50 microeq/L, the criteria varied greatly in their R values.

Quality Control↗