Presentation on theme: "Quality Assurance in the clinical laboratory"— Presentation transcript:
1 Quality Assurance in the clinical laboratory Lecture 1
2 DefinitionQuality assurance is the coordinate process of providing the best possible service to the patient and physicianQuality 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 theRight time, on theRight specimen, from theRight patient,With the result interpretation based on,Correct reference data,and at the Right price.
4 Sources of ErrorErroneous results are at best a nuisance; at worst, they have potential for causing considerable harmErrors can be minimized by:careful adherence to robust, agreed protocols at every stage of the testing processthis 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 activitiesAssessment ProceduresCorrective actions
7 Preventive Activities Prevent errorsImprove accuracy and precisionMethod selectionCareful laboratory designHiring of competent personnelDevelopment of comprehensive procedure manualsEffective preventive maintenance programs
8 Assessment Procedures Monitor the analytical processDetermine the type of errorDetermine the amount of errorDetermine the change in accuracy and precisionThese activities include:The testing of quality control materialPerforming instrument function checksParticipating 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 servicesReview of workTroubleshooting 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 procedureControl sample is processed along with the patient samples and the results are comparedQuality control is an important part of quality assurance program
11 Accuracy and Precision Accuracy is the measure of "truth" of a resultAccurate 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 errorPrecision is completely independent of accuracy or truthA procedure can be precise, as determined by repeat analysis, but the result can be inaccurateThree 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 PrecisionNeitherGood precisionNor AccuracyGood Accuracy Good PrecisionGood Precision Only
14 Accuracy and Precision Accuracy: both are equally precise, but in method D the mean value differs from the true valueThe mean for method C is equal to the true valueBoth methods are equally precise, but method C is more accurate
15 PrecisionThe graph shows the distribution of results for repeated analysis of the same sample by different methodsPrecision: the mean value is the same in each case, but the scatter about the mean is less in method A than in method BMethod A is, therefore, more precise15
16 When Errors Occur ?Errors occur when there is a loss of accuracy and precisionA primary goal of quality assurance is to reduce and detect errors or to obtain the best possible accuracy and precision
17 Types of ErrorsMistakes jeopardize patient care and must be detected and avoided at all timesrandom errorssystematic errors
18 Random Errors Occur without prediction or regularity Affect measurement of precision and causes data to be scattered moreRandom 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 resultsCauses the mean of a data set to differ from the accepted valueExamples include:Incorrect instrument calibrationUnprecise or malfunctioning dilutors and pipettesReagents that lost their activity
20 Systematic Errors Types of systematic errors proportional systematic error or biasIt grows larger as the concentration of analyte growsconstant systematic error "constant bias"A constant amount over the entire range of the analysis process.
21 Types of ErrorsThe 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 samplesThe 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 levelsUsing an independent analytical methodThe 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 methodsPerforming blank determinationsVarying the Sample SizeAs 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 physicianImprovement of precision and accuracyEarly detection of mistakesMore efficient and cost effective use of materials and personnelMeeting the requirements of inspection and accreditation agenciesDevelopment of accurate and concise procedures and manualsMeasure of productivity of personnel and instrumentation.
24 Personnel, Staff Development & Quality Assurance The most expensive and complex resource in any organization is its' employeesChoosing 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