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Quality Assurance in the clinical laboratory

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Presentation on theme: "Quality Assurance in the clinical laboratory"— Presentation transcript:

1 Quality Assurance in the clinical laboratory
Lecture 1

2 Definition Quality assurance is the coordinate process of providing the best possible service to the patient and physician Quality assurance includes monitoring and controlling: the competence of personnel, quality of materials, methods, reagents and instruments, and the reliable reporting of test results

3 WHO Definition Quality assurance has been defined by WHO as:
The total process whereby the quality of the laboratory reports can be guaranteed. It has been summarized as the: Right result, at the Right time, on the Right specimen, from the Right patient, With the result interpretation based on, Correct reference data, and at the Right price.

4 Sources of Error Erroneous results are at best a nuisance; at worst, they have potential for causing considerable harm Errors can be minimized by: careful adherence to robust, agreed protocols at every stage of the testing process this means a lot more than ensuring that the analysis is performed correctly. Errors can occur at various stages in the process: pre-analytical, occurring outside the laboratory, analytical, occurring within the laboratory, post-analytical, whereby a correct result is generated but is incorrectly recorded in the patient's record,


6 Aspects of a Good Quality Assurance Program
A good quality assurance program has three major aspects: Preventive activities Assessment Procedures Corrective actions

7 Preventive Activities
Prevent errors Improve accuracy and precision Method selection Careful laboratory design Hiring of competent personnel Development of comprehensive procedure manuals Effective preventive maintenance programs

8 Assessment Procedures
Monitor the analytical process Determine the type of error Determine the amount of error Determine the change in accuracy and precision These activities include: The testing of quality control material Performing instrument function checks Participating in proficiency testing programs (e.g. survey programs of accrediting agencies)

9 Corrective Actions Correct errors after discovery
Communication with the users of laboratory's services Review of work Troubleshooting of instrument problems

10 Quality Assurance versus Quality Control
Quality control involves the use of control samples to monitor the precision and accuracy of a test procedure Control sample is processed along with the patient samples and the results are compared Quality control is an important part of quality assurance program

11 Accuracy and Precision
Accuracy is the measure of "truth" of a result Accurate results reflect the "true" or correct measure of an analyte or identification of a substance

12 Accuracy and Precision
Precision is the expression of the variability of analysis, reproducibility of a results, or an indication of the amount of random error Precision is completely independent of accuracy or truth A procedure can be precise, as determined by repeat analysis, but the result can be inaccurate Three terms are widely used to describe the precision of a set of replicate data: standard deviation; variance; coefficient of variation

13 Good Accuracy Good Precision
Accuracy and Precision Neither Good precision Nor Accuracy Good Accuracy Good Precision Good Precision Only

14 Accuracy and Precision
Accuracy: both are equally precise, but in method D the mean value differs from the true value The mean for method C is equal to the true value Both methods are equally precise, but method C is more accurate

15 Precision The graph shows the distribution of results for repeated analysis of the same sample by different methods Precision: the mean value is the same in each case, but the scatter about the mean is less in method A than in method B Method A is, therefore, more precise 15

16 When Errors Occur ? Errors occur when there is a loss of accuracy and precision A primary goal of quality assurance is to reduce and detect errors or to obtain the best possible accuracy and precision

17 Types of Errors Mistakes jeopardize patient care and must be detected and avoided at all times random errors systematic errors

18 Random Errors Occur without prediction or regularity
Affect measurement of precision and causes data to be scattered more Random errors occur as the result of: Carelessness, Inattention, when taking short cuts in procedures, Mislabeling specimens, Incorrect filing of reports, Reporting of wrong result to the wrong patient

19 Systematic Errors Errors within the test system of methodology
Affect the accuracy of results Causes the mean of a data set to differ from the accepted value Examples include: Incorrect instrument calibration Unprecise or malfunctioning dilutors and pipettes Reagents that lost their activity

20 Systematic Errors Types of systematic errors
proportional systematic error or bias It grows larger as the concentration of analyte grows constant systematic error "constant bias" A constant amount over the entire range of the analysis process.

21 Types of Errors The dashed line represents ideal method performance where the test method and the comparative method give exactly the same results. The bottom line shows the effect of a proportional systematic error, where the magnitude of the error increases as the test result gets higher. The top line shows the effect of a constant systematic error, where the whole line is shifted up and all results are high by the same amount. Note that these results will also be subject to the random error of the method, therefore the actual data points would scatter about the line as illustrated in the figure. The range of this scatter above and below the line provides some idea of the amount of random error that is present.

22 Detecting Systematic Errors
Analyzing standard samples The best way to estimate the bias of an analytical method is by analyzing standard reference materials, materials that contain one or more analytes at well-known or certified concentration levels Using an independent analytical method The independent method should differ as much as possible from the one under study to minimize the possibility that some common factor in the sample has the same effect on both methods Performing blank determinations Varying the Sample Size As the size of a measurement increases, the effect of a constant error decreases. Thus, constant errors can often be detected by varying the sample size.

23 Benefits of an Effective quality Assurance Program
Correct and timely presentation of data to the physician Improvement of precision and accuracy Early detection of mistakes More efficient and cost effective use of materials and personnel Meeting the requirements of inspection and accreditation agencies Development of accurate and concise procedures and manuals Measure of productivity of personnel and instrumentation.

24 Personnel, Staff Development & Quality Assurance
The most expensive and complex resource in any organization is its' employees Choosing the appropriate individuals for the job and managing them effectively is one of the most difficult and powerful means available to prevent errors in the laboratory

25 Tiers of Responsibility

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