QUALITY ASSURANCE IN THE CLINICAL LABORATORY

Lecture 1

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

• 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.

WHO Definition

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,

Aspects of a Good Quality Assurance Program

• A good quality assurance program has three major aspects:

1. Preventive activities

2. Assessment Procedures

3. Corrective actions

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

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)

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

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

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

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

Good Accuracy Good

Precision

Good Precision Only

Neither Good precision Nor Accuracy

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

Accuracy and 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

Precision

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

Types of Errors

• Mistakes jeopardize patient care and must be detected and avoided at all times • random errors• systematic errors

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

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

Systematic Errors

• Types of systematic errors

A. proportional systematic error or bias • It grows larger as the concentration of analyte grows

B. constant systematic error "constant bias" • A constant amount over the entire range of the analysis

process.

The dashed line represents ideal method performance where the test method and the comparative method give exactly the same results.

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.

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.

Types of ErrorsTypes of Errors

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.

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.

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

Tiers of Responsibility