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PubMed1994

Quality control and quality management of alternate-site testing.

Quality is an important attribute of clinical laboratory results; however, methods for defining acceptable quality may not be entirely agreed upon. In addition, confusion over quality is added when laboratory testing is moved to alternate sites. As quality parameters are designed for novel laboratory delivery systems, it will be best to use novel approaches that build on already well-defined principles of laboratory quality management.

Clinical Laboratory Techniques↗
PubMedDate not supplied

External quality control program for inter-laboratory quality control.

BACKGROUND: The accuracy and precision of tumor marker testing is of high clinical importance requiring the implementation of effective quality control procedures in the diagnostic laboratory. An external quality control program including an inter-laboratory comparison could be of help in improving the quality of test results. MATERIALS AND METHODS: Laboratories using BIOREF reference material sent their routine internal quality control results of each monthly control period to the evaluation center for statistical analysis and inter-laboratory comparison. RESULTS: The inter-laboratory comparison showed that the mean values of test results obtained by different laboratories can vary considerably especially when different test kits are used. A comparison of test results of laboratories using the same test kit showed much better correlation but discrepancies of coefficients of variation between these laboratories were still observed. CONCLUSION: An external quality control program revealed problems in the accuracy and precision of tumor marker test results in the individual laboratory, which could serve as a basis for the improvement of test performance.

Biomarkers, Tumor↗
PubMed1980

Problems associated with clinical chemistry quality control materials.

Quality control methods and materials are widely used to monitor each and every facet of clinical chemistry laboratory performance. Quality control materials are also used in evaluation of methods and as secondary standards. A wide range of liquid and lyophilized materials are available from commercial sources and are prepared in individual laboratories. Many problems arise in the use of quality control materials. Problems discussed in this review include the use of nonhuman based materials and additives of animal origin, the physical and chemical characteristics of quality control materials that differentiate such samples from those from patients, attempts to generate quality control materials with elevated levels of particular analytes, the difficulties in handling and storage of quality control materials, the dangers of hepatitis, and the stability of quality control materials both during storage in the laboratory and after their reconstitution. The advantages and disadvantages of liquid and lyophilized quality control materials are discussed. The assignation of analyte values is of particular importance as the current trend is to consider inaccuracy of laboratory methods in addition to imprecision. This review assesses relevant publications in an area of fundamental importance to quality control in clinical chemistry.

Animals↗
PubMed1998

In vitro susceptibility testing and quality control parameters for sarafloxacin (A-56620): a fluoroquinolone used for treatment and control of colibacillosis in poultry. Quality Control Study Group.

Sarafloxacin (formerly A-56620) is a fluoroquinolone recently introduced into veterinary practice for the therapy of colibacillosis and other indicated infections. Sarafloxacin was noted to be very active and comparable to ciprofloxacin and enrofloxacin for inhibiting 823 strains from a wide variety of species at < or = 1 or < or = 2 micrograms/mL. In vitro susceptibility tests for sarafloxacin using National Committee for Clinical Laboratory Standards (NCCLS) methods were also studied and interpretive criteria for Escherichia coli-associated colibacillosis isolates were proposed: susceptible at < or = 0.06 microgram/mL (> or = 25 mm) and resistant at > or = 0.25 microgram/mL (< or = 21 mm). Sarafloxacin agar dilution MIC results were approximately one log2 dilution higher than broth microdilution endpoints. The interpretive criteria demonstrated a low error rate of 5.9%, with a very major rate of only 0.5% (correlation coefficient between methods = 0.94). Quality control trials in six laboratories established MIC and zone diameter (5-microgram disk) limits for the NCCLS recommended strains: for the broth microdilution test, E. coli ATCC 25922 = 0.008 to 0.03 microgram/mL, Pseudomonas aeruginosa ATCC 27853 = 0.12 to 1 microgram/mL, Enterococcus faecalis ATCC 29212 = 0.5 to 2 micrograms/mL, and Staphylococcus aureus ATCC 29213 = 0.06 to 0.25 microgram/mL; and for the disk diffusion test, E. coli ATCC 25922 = 30 to 36 mm, S. aureus ATCC 25923 = 25 to 30 mm, and P. aeruginosa ATCC 27853 = 23 to 29 mm. These criteria for in vitro tests with sarafloxacin should enable the longitudinal monitoring of its activity against the indicated pathogens and allow detection of emerging resistant populations that may necessitate altered dosing regimens.

Animals↗
PubMed1982

A flexible and versatile program for blood-gas quality control.

A quality control program which related quality control data to maintenance procedures has been developed. Whole blood tonometered at three levels of pCO2 and pO2 is used as the quality control material. A key feature of the program is that control values are independent of barometric pressure. The recording format consolidates results at all levels for each constituent, and permits direct comparison with maintenance procedures or electrode changes. The tonometry system consists of a precision gas mixer, Corning Model 192, and a two-channel syringe tonometer, Corning Model 184. This system provides several advantages for quality control, including: (1) use of Levy-Jenning charts with constant "mean values" for tonometered blood; (2) evaluation of electrode linearity over a wide range of partial pressures; and (3) multiple values for each parameter tested. Recovery of theoretical values over a broad range of partial pressure allows more accurate assessment of proportional response for assignment of pO2 "correction factors." Differences between instruments may also be investigated in closer detail.

Blood Gas Analysis↗
PubMed1985

Use of commercially prepared control sera as quality control materials for spectrophotometric bilirubin determinations in amniotic fluid.

The visible absorption spectra of dilutions of commercially prepared chemistry control sera closely mimic those of jaundiced amniotic fluids in cases of fetal rhesus isoimmunization. The authors have assessed the use of these materials for the quality control of net absorbance measurements at 450 nm on amniotic fluids. The authors conclude that they are excellent quality control materials because of their ready availability, low cost, long-term stability, wide range of bilirubin concentrations, and their close resemblance to jaundiced amniotic fluids with respect to light absorption and scattering, sensitivity to light, and pigment extractability into chloroform. Their spectra also contain a maximum at 410 nm, so these materials can also be used as controls for net absorbance measurements at 410 nm, a determination that indicates the extent of heme or meconium pigment interference with net absorbance measurements at 450 nm. These materials both supplement and complement the requisite spectrophotometric performance checks of wavelength calibration and photometric accuracy.

Amniotic Fluid↗
PubMedDate not supplied

Use of the selective linogram in cardiac tomography quality control.

BACKGROUND: Quality control for detection of patient motion is essential in tomographic myocardial imaging. Despite significant limitations, the summation image or conventional "linogram" has long been advocated as a useful image in the detection of vertical motion. In this study a new quality control image entitled the "selective linogram" is proposed to replace the summation image in routine cardiac single-photon emission cardiac tomography (SPECT) quality control. The selective linogram is constructed in a manner somewhat analogous to the sinogram. In the sinogram, each row represents a different projection angle; in the selective linogram each column represents a different projection angle. METHODS AND RESULTS: After selection of eight motion-free studies from acquisitions at our clinical center, vertical motion of various types (bounces, shifts, and creep) were added to the projection frames. Summation image and selective linogram quality control images from these motion-containing studies and the original motion-free studies were presented in a blinded manner to two observers for scoring of patient motion. The selective linogram was significantly more accurate in allowing detection of vertical motion than was the summation image (accuracy 89% vs 47%). CONCLUSIONS: The selective linogram image is markedly superior to the summation image for the detection of vertical patient motion during cardiac SPECT. This new technique can be a valuable aid in SPECT quality control.

Heart↗
PubMed1997

Quality control programme in mammography: second level quality controls.

Mammography is the most reliable method by which to detect lesions in the breast. Since contrast between normal and pathological areas in the breast is extremely low, mammographic image quality should reach high standards without exceeding acceptable exposure levels for the breast. A quality control programme in mammography has been implemented. This programme is subdivided into two levels. The first consists of simple daily checks of image quality and film processing, while the second deals with more complex checks of mammographic unit, screen-film system, darkroom, illuminators, viewing conditions and reference dose determination. The values of all the parameters undergoing measurement are compared with the limiting values given by National and International Protocols. This paper describes the second level controls carried out every 6 months by the medical physicist. The parameters described are only those which have been studied and analysed in detail since the quality control programme in mammography was implemented. Such parameters (kilovoltage, focal spot dimension, half value layer, tube output, automatic exposure control system, screen-film characteristic curve and mean glandular dose) were measured during the period 1991-1995 and the results summarised. The values obtained prove the constant correct functioning of the equipment.

Breast↗
PubMed1984

The impact of quality control materials on the performance of an internal quality control system: 1. General considerations.

Quality assurance in clinical chemistry is based on statistical control procedures designed to maintain a certain level of quality. Decisions about acceptance or rejection of analytical series are made primarily from measurements of quality control materials. Such materials are most often of non-human origin; this may lead to false decisions due to non-identity of patient samples and quality control material. We have investigated the significance of non-identity between patient and control materials by running two separate quality control systems in parallel. A regular system used for acceptance or rejection of series, and a parallel system used for registration of the actual quality of the analytical routine work. The results from the latter system have not been available for the operator handling the control system used in routine work. Our study has confirmed the validity of an internal quality control system to achieve a certain level of analytical stability as expressed by the short-term and long-term precision. However, because ideal control materials are not always available, additional procedures to control accuracy, specificity, and detectability may be necessary. The usefulness of such procedures to properly handle error signals from quality control systems has been demonstrated.

Chemistry, Clinical↗
PubMed1992

Comparative study of certified reference materials and quality control materials for the quality assurance of blood-lead determination.

In order to ensure a high standard in the analytical methods used to determine lead in blood, reference materials, quality control materials and several quality assessment schemes exist. However, since 1988 the blood lead level in the European Community has decreased owing to a decline in environmental and occupational exposure; consequently there is a need for certified reference materials (CRMs) at low level. A study of the biological CRMs for blood lead, CRMs 194-196 from the European Community Bureau of Reference (BCR) and the quality control materials STE 901-906 from Nyegaard A/S, and AMI B601-B604 and AMI B701-B705 from the Danish National Institute of Occupational Health (AMI), was made in order to evaluate the control materials AMI B701-B705 against the CRMs 194-196, and to verify the homogeneity and influence of the biological matrix of commercially available blood-lead quality control materials. Internal quality control data were collected and an interlaboratory study was carried out on lyophilized human blood versus lyophilized bovine blood certified for lead. The calculated standard deviations for the BCR CRMs were comparable to the standard deviations for AMI control materials, although the biological matrix was different. No significant difference was demonstrated between the blood-lead levels certified by BCR in 1985 and the levels measured by AMI in 1991, indicating the homogeneity and stability of the lyophilized materials. All analytical results were obtained from selected international laboratories by using atomic absorption spectrometry and anodic stripping voltammetry. The study emphasizes the need for CRMs, control materials and quality assessment schemes for trace elements in biological fluids.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1998

Internal quality control and external quality assurance in the IVF laboratory.

The existence of internal quality control programmes and external quality assurance schemes is important in enabling the maintenance of good service to patients. All aspects of our work in laboratories involved in the diagnosis and treatment of human infertility can benefit from such programmes and schemes, moving the work from being a subjective art form to an objective science. Equally, many clinical procedures are amenable to such scrutiny. Acceptance and introduction of such schemes and programmes will rely initially on the self-motivation of the laboratories themselves and then pressure brought to bear by accrediting authorities.

Fertilization in Vitro↗
PubMed2000

Serum tumour markers: from quality control to total quality management.

Since the first clinical use of tumour markers, quality assurance has been considered only in a restrictive manner, that is, as a surveillance of the analytical process. In other words, quality assessment was roughly viewed as a synonymous with quality control. This is not surprising, since tumour markers are almost exclusively assayed by radioimmunoassays, whose analytical performance were suboptimal in the 1970s. Furthermore, tumour marker concentrations in biological fluids were very low (in the ng range); in addition, primary standards were not available and dose-response curves were set up with conventional calibrators. Therefore, quality control programmes have become mandatory to restrict intra- and inter-laboratory variability.

Journal Article↗