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PubMed1991

Composite multivariate quality control using a system of univariate, bivariate, and multivariate quality control rules.

We propose a composite multivariate quality control (CMQC) system to control simultaneously measured variables. This system is designed to detect unacceptable trends and systematic error in one or more variables, unacceptable random error in one or more variables, and unacceptable changes in the correlation structure in any pair of variables. It is also designed to be tolerant of missing data, to be capable of rejecting as few as one or as many as all variables in a run, and to provide the analyst with control statistics and graphics that logically relate to sources of analytical error. Quality control rules for univariate, multivariate, and correlation conditions are incorporated in the system, as are plots displaying CMQC statistic values and control limits for univariate, multivariate, and correlation parameters. We also discuss advantages of the CMQC over the T2 and principal component multivariate quality control methods. We demonstrate the CMQC procedure using data from a laboratory process in which 40 variables were measured during 40 characterization runs and 23 runs analyzing unknowns.

Chemistry Techniques, Analytical↗
PubMed1999

Comparative antimicrobial activity of gatifloxacin tested against Streptococcus spp. including quality control guidelines and etest method validation. Quality Control Study Group.

Gatifloxacin (formerly AM-1155 or CG 5501) is a new 8-methoxy fluoroquinolone with enhanced activity against Gram-positive cocci, especially Streptococcus pneumoniae and other streptococci. Recent clinical strains (599 isolates) were tested against gatifloxacin, three comparison fluoroquinolones, and penicillin by the reference broth microdilution, Etest (AB BIODISK, Solna, Sweden) and standardized disk diffusion methods (5 micrograms gatifloxacin disk). Gatifloxacin (MIC90, 0.5 microgram/ml) activity was generally comparable to that of trovafloxacin (MIC90, 0.25 microgram/ml), or sparfloxacin (MIC90, 0.5 microgram/ ml) and markedly superior to ofloxacin (MIC90, 2-4 micrograms/ml) against the streptococci. Rates of penicillin non-susceptibility were 41.9, 38.0, and 16.2% for S. pneumoniae (301 strains), viridans group streptococci (150 strains), and beta-haemolytic streptococci (148 strains). Etest results correlated well (95.7-100.0% +/- one log2 dilution) with the reference MIC results, but Etest tended to have elevated gatifloxacin MIC results compared to the broth microdilution method for the highly resistant isolates (MICs, > 2 micrograms/ml). Gatifloxacin disk zone diameters correlate well to reference MICs for all streptococci and proposed interpretive criteria (susceptible at < or = 1 microgram/ml or > or = 18 mm, and resistant at > or = 4 micrograms/ml or < or = 14 mm) did not produce discords between method results (absolute agreement). A nine laboratory quality control (QC) study conforming to the National Committee for Clinical Laboratory Standards (NCCLS) Guideline M23-T3 studied S. pneumoniae ATCC 49619 and gatifloxacin. Proposed ranges for QC of NCCLS tests were 0.12-0.5 microgram/ml for the broth microdilution test and 24-31 mm for the disk diffusion method. These reported results indicate that gatifloxacin was a potent fluoroquinolone with extensive activity against streptococcal isolates. In vitro test methods to measure this activity appear accurate and comparable; and QC guidelines have been established for routine clinical laboratory use pending approval by the NCCLS and the Food and Drug Administration (FDA).

Anti-Infective Agents↗
PubMed1984

The impact of quality control materials on the performance of an internal quality control system: 3. Experiences from S-triiodothyronine analysis.

In this subproject a method for S-triiodothyronine was used for evaluation of the specified system of internal quality control. Decisions on acceptance and rejection of series were based on results from a human pool with triiodothyronine concentration at the upper reference limit. In the parallel system specimens from patients and from healthy individuals were used in combination with artificial materials so that changes in accuracy, specificity, and detectability could be disclosed. The results were examined for false rejections and false acceptances. For all the seven rejections in 117 series due to a mean rule of 8 controls with a pfr of 0.01, the parallel system supported the decisions. In eight occasions the series were rejected due to a range rule with a pfr of 0.05; one rejection was confirmed by the parallel system and the remaining seven times out of the 117 series were close to the expected five percent of false rejections. A small systematic change in standardization of about eight percent was too small to be recognized by the quality control system. The specificity was not changed during the investigation period; all of the systematic changes were caused by variations in the standard materials. In conclusion the investigation confirmed the validity of the specified system of internal quality control.

False Negative Reactions↗
PubMed1980

Quality control revisited.

Quality Control is a way of life for today's clinical laboratory and the direct responsibility of its director. While individual laboratory sections require quality control procedures of ever-growing complexity, there also is need for an overview and the statement of policies that concern the laboratory as a whole. In the August 1977 issue of Pathologist (I & A Center, pp. 442-444), Dr. Diamond, regional commissioner for the northeast, described a guide for a comprehensive quality control statement. The following article is an expansion and development of that statement.

Hospitals↗
PubMed1981

Infection control as a quality control in an integrated hospital quality assurance program.

I have discussed infection control in the context of a quality control system in a hospital. To date hospital "quality assurance" has been unfocused, retrospective, and CME related-an inappropriate response to such quality problems as inappropriate antibiotic usage, hospital related infection, and professional (malpractice) liability. I have suggested that the control paradigm (a concurrent signal leads to response system) may provide the approach needed to enhance the effectiveness of the whole hospital quality assurance effort.

Cross Infection↗
PubMed2001

Electronic quality control, the total testing process, and the total quality control system.

Traditional statistical quality control (QC) using matrix controls is often difficult to implement in point-of-care settings. Alternative QC procedures, such as electronic QC, have been developed by many manufacturers and approved for use by regulatory and accreditation organizations. Electronic QC usually involves the substitution of an electrical signal for the signal that would normally be generated by a sensor responding to an analyte in a specimen; sometimes an artificial nonliquid sample is substituted to cause the sensor to generate an electrical signal. The usefulness of electronic QC can be assessed by identifying the steps in the total testing process that are being monitored. An example is provided for blood gas measurements to illustrate the steps that can be monitored by different types of QC procedures and materials. The need to monitor all of the steps generally requires a combination of procedures and materials, or a total QC system that includes electronic QC, matrix controls, and even real patient specimens. Electronic QC is an essential part of the total QC system, but is not by itself sufficient.

Clinical Chemistry Tests↗
PubMed2006

Quantitative assessment of computed radiography quality control parameters.

Quality controls for testing the performance of computed radiography (CR) systems have been recommended by manufacturers and medical physicists' organizations. The purpose of this work was to develop a set of image processing tools for quantitative assessment of computed radiography quality control parameters. Automatic image analysis consisted in detecting phantom details, defining regions of interest and acquiring measurements. The tested performance characteristics included dark noise, uniformity, exposure calibration, linearity, low-contrast and spatial resolution, spatial accuracy, laser beam function and erasure thoroughness. CR devices from two major manufacturers were evaluated. We investigated several approaches to quantify the detector response uniformity. We developed methods to characterize the spatial accuracy and resolution properties across the entire image area, based on the Fourier analysis of the image of a fine wire mesh. The implemented methods were sensitive to local blurring and allowed us to detect a local distortion of 4% or greater in any part of an imaging plate. The obtained results showed that the developed image processing tools allow us to implement a quality control program for CR with short processing time and with absence of subjectivity in the evaluation of the parameters.

Calibration↗
PubMed1984

The impact of quality control materials on the performance of an internal quality control system: 2. Experiences from S-calcium analysis.

In this subproject the analysis of S-calcium was used for evaluation of the specified system of internal quality control. Decisions on acceptance or rejection of series were based on a non-human pool with a calcium concentration near the upper reference limit. In the parallel system, specimens from patients and healthy individuals were used together with other non-human pools to disclose changes in accuracy. The results were examined for false rejections and false acceptances. In all the rejections based on a mean rule with 9 controls and a pfr of 0.01, the parallel system supported the decisions. On 18 occasions the series were rejected based on a range rule with a pfr of 0.05. Ten of the rejections were confirmed by the parallel system, and the remaining eight times of the 165 series were close to the expected five per cent of false rejections. The matrix effect estimated from the human and non-human serum pools was less than 15 per cent of the total variation. This supported the convenient use of non-human control materials in the analysis of S-calcium. The total variation, CVt, was estimated to be in the range of 0.027-0.030. The median of the patient results could be a valuable tool in quality control, whereas the mean of patient results within the reference limits is of no value. In conclusion, the investigation confirmed the validity of a system for internal control of a specified quality.

Analysis of Variance↗
PubMed2005

Using an independent quality control software program, EZ Runs, to monitor quality control procedures for a bench-top coagulation analyzer.

BACKGROUND: Comprehensive quality control (QC) procedures are necessary to ensure accurate analytic method performance. Highly automated systems typically have inherent QC programs that facilitate performance and maintenance of QC procedures; however, for bench-top analyzers that lack internal systems, independent QC programs must be used. OBJECTIVE: The goal of this study was to evaluate the adaptability of an independent QC program, EZ Runs (Westgard QC Inc, Madison, WI, USA), to the maintenance of QC procedures for a mechanical, bench-top coagulation unit and to compare the results with our current, manual, QC method in a qualitative way. METHODS: A QC application file for activated partial thromboplastin time (aPTT) performed on a STart4 (Diagnostica Stago, Parsippany, NJ) was created in EZ Runs. Results were recorded and interpreted using this software package as well as the current, manual, QC method. RESULTS: EZ Runs was adaptable to QC monitoring for the bench-top analyzer, and the program permitted identification of both random and systematic errors not detected by the manual QC system. CONCLUSIONS: EZ Runs improved the performance and maintenance of QC procedures for this bench-top coagulation analyzer. The results indicated the need to improve staff training in assay performance and QC interpretation. In addition, use of the software program indicated that a multirule QC design was needed to monitor assay performance.

Animals↗
PubMed1999

Gas chromatographic-tandem mass spectrometric determination of anabolic steroids and their esters in hair. Application in doping control and meat quality control.

We have developed a powerful and simple sensitive method for testing hair for anabolic steroids and their esters. A 100-mg amount of powdered hair was treated with methanol in an ultrasonic bath for extraction of esters, then alkaline digested with 1 M NaOH for an optimum recovery of other drugs. The two liquid preparations were subsequently extracted with ethyl acetate, pooled, then finally highly purified using a twin solid-phase extraction on amino and silica cartridges. The residue was derivatized with N-methyl-N(trimethylsilyl)-trifluoracetamide (MSTFA) prior to injection. Analysis was conducted by gas chromatography coupled to a triple quadrupole mass spectrometer. The generally chosen parent ion was the molecular ion while two daughter ions were selected for each compound with collision energies ranging from -16 to -21 eV. Internal standards were nandrolone d3 for non-esterified drugs and testosterone phenyl propionate for esters. The limits of detection calculated from an analysis of the blanks (n=30) were 0.08 pg/mg for nandrolone, 6.20 pg/mg for boldenone, 0.07 pg/mg for methyl testosterone, 0.15 pg/mg for ethinyl estradiol, 2.10 pg/mg for metandienone, 0.86 pg/mg for testosterone propionate, 0.95 pg/mg for testosterone cypionate, 1.90 pg/mg for nandrolone decanoate, 3.10 pg/mg for testosterone decanoate and 4.80 pg/mg for testosterone undecanoate. Application to doping control has been demonstrated. In a series of 18 sportsmen, two tested positive for anabolic steroids in hair whereas urinalysis was negative for both of them. The first positive case was nandrolone and the second case concerned the identification of testosterone undecanoate. Measured in 10 white males aged between 22 and 31 years, the testosterone concentration was in the range 1.7-9.2 pg/mg (mean=5.0 pg/mg). The method was also applied in meat quality control. Of the 187 analyses realized based upon hair and urine sampling in slaughter houses, 23 were positive for anabolic steroids in hair: one case for boldenone, one case for metandienone, two cases for testosterone propionate, three cases for nandrolone, five cases for testosterone decanoate and 11 cases for methyl testosterone. In the meantime, urinalysis was always negative for these drugs or their metabolites.

Adult↗
PubMed1977

Combined Shewhart-cusum control chart for improved quality control in clinical chemistry.

We describe the adaptation of the decision limit cumulative sum method (cusum) to internal quality control in clinical chemistry. With the decision limit method, the cusum is interpreted against a numerical limit, rather than by use of a V-mask. The method can be readily implemented in computerized quality-control systems or manually on controls charts. We emphasize the manual application here and demonstrate how the technique can be implemented on existing Shewhart or Levey-Jennings control charts. This permits both cusum and Shewhart control rules to be used simultaneously on a single control chart and also minimizes the data calculations necessary for the cusum method. Computer simulation studies are used to determine the performance characteristics of several different cusum rules, alone and in combination with a Shewhart rule. These studies indicate that improvements in existing quality-control systems should be possible by addition of this simple cusum method and by use of a combined Shewhart-cusum control chart. This should be particularly advantageous when introducing the cusum method in laboratories with manual quality-control systems.

Chemistry, Clinical↗
PubMed1990

[Current status and trends in quality control in parasitology and mycology].

The survey of the results of the control quality in Parasitology and Mycology showed in general an improvement in the correct diagnosis for the specimen analysed (preparations of parasites, smears, stools, sera, fungal cultures). The wrong diagnosis of Ascaris lumbricoides eggs in stools diminished from 5% to 1.5%. The trichrome Gomori-Wheatley stain technic on smears in PVA was introduced. 16 reference or national standards sera for the parasitological serology, including 6 for toxoplasmosis and one for candidiasis were established. The increasing number of participants (more than 4,000) and particularly for the serology of toxoplasmosis showed the interest of the biologists for the quality of their tests.

Animals↗
PubMedDate not supplied

[Evaluating an internal quality control procedure: application to multidimensional control].

Internal quality control keeps in constant evolution in the industrial world. Introducing in clinical chemistry new QC methods derived from the industrial practice raises the point of the means for their evaluation. The main evaluation criteria are discussed in this paper. The importance of ARL (average run length) as a key-criterion of the efficiency of a quality control procedure is stressed. These principles were applied to the multivariate approach of multilevel control with the Hotelling's T2. This method led to a better detection of random errors than the independently managed conventional Shewhart (Levey- Jennings) charts. Applied to systematic errors, both methods gave similar results with a certain lack of sensitivity. However the multivariate method can be sensitised using EWMA (exponentially weighted moving average), a method specific for improved bias detection. EWMA efficiency outperforms that of the older systems of rules. Moreover, in any kind of error, multivariate approach secures a well-defined false rejection rate, whereas this rate is dependant on unknown inter-level correlation coefficients in conventional QC.

Bias↗
PubMedDate not supplied

How much quality control is enough? A cost-effectiveness model for clinical laboratory quality control procedures (illustrated by its application to a ligand-assay-based screening program).

Quality assurance testing represents a substantial proportion of the clinical laboratory budget, but current guidelines are based on criteria that pertain to analytic error rather than to optimization of the cost-effectiveness of patient care. A general Bayesian mathematical model for the cost-effectiveness of assay quality control has been developed, and is demonstrated using previously published data. The cost-effectiveness of quality assurance as defined here depends upon the prevalence of disease, the shapes of the distributions of test results observed in the non-diseased and diseased populations, the decision limit selected for labeling results positive or negative, the costs and benefits associated with each of the possible therapeutic outcomes, the magnitude of random and systematic analytical errors, the statistical power of the quality control test in use, the costs associated with delays due to re-assay, and the proportion of total test cost attributable to quality control procedures. Given current clinical laboratory practice, much of this information will not be routinely available. The model combines these factors into a simple equation with three terms: one for the cost of the original and any required repeat laboratory analyses, one for the cost of delay entailed by the rejection of an assay batch, and one for the change in total costs consequent to rejection of erroneous assay results.

Clinical Laboratory Techniques↗
PubMed1979

An investigation into the distribution of radial immunodiffusion quality control data.

Quality control data from routine radial immunodiffusion assays for IgG, IgA, IgM, C3, C4 and alpha1-antitrypsin were tested by the Kolmogorov--Smirnov procedure for gaussian distribution. All but alpha1-antitrypsin were nongaussian in type. Further analysis of these date by plotting on log-normal probability paper showed them to have a log-normal distribution. Treatment of the date by either gaussian or nonparametric statistical methods produced little difference in confidence limits. It does not appear necessary to use nonparametric methods to calculate confidence limits from quality control data for the procedures studied.

Complement C3↗