Quality control
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Promotion of quality control and continuous improvement of the total testing process, including preanalytical and postanalytical phases
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Quality control
- 1. Tapeshwar Yadav (Lecturer) BMLT, DNHE, M.Sc. Medical Biochemistry
- 2. Three principles of clinical labThree principles of clinical lab
- 3. What is Quality?What is Quality?
- 6. Prerequisite for an effective lab servicePrerequisite for an effective lab service
- 7. Steps in obtaining a laboratory testSteps in obtaining a laboratory test
- 8. Lab testing processes and their potential errorsLab testing processes and their potential errors
- 9. Lab testing processes and their potential errorsLab testing processes and their potential errors
- 10. Lab testing processes and their potential errorsLab testing processes and their potential errors
- 11. Lab testing processes and their potential errorsLab testing processes and their potential errors
- 12. Lab testing processes and their potential errorsLab testing processes and their potential errors
- 13. Lab testing processes and their potential errorsLab testing processes and their potential errors
- 14. Elements of a QA/QC ProgramElements of a QA/QC Program
- 15. Quality Control: Technical ProceduresQuality Control: Technical Procedures
- 30. Control of analytical quality using statistical methods and control charts Control of analytical quality using statistical methods and control charts
- 33. l
- 42. CUSUM Control ChartCUSUM Control Chart
Editor's Notes
- Animated 3-D cube with changing pictures (Basic) Tip: This example uses six pictures grouped in four sets of three, so that during the animation, various pictures appear on the cube. To reproduce the effects on this slide, do the following: On the Home tab, in the Slides group, click Layout, and then click Blank. On the Insert tab, in the Illustrations group, click Picture. In the Insert Picture dialog box, select a picture, and then click Insert. Select the picture. Under Picture Tools, on the Format tab, in the Size group, click the Size and Position dialog box launcher. In the Format Picture dialog box, resize or crop the image so that the height is set to 3.42โ and the width is set to 3.42โ. To crop the picture, click Crop in the left pane, and in the Crop pane, under Crop position, enter values into the Height, Width, Left, and Top boxes. To resize the picture, click Size in the left pane, and in the right pane, under Size and rotate, enter values into the Height and Width boxes. Under Picture Tools , on the Format tab, in the Picture Styles group, in the bottom right corner click the Format Shape dialog box launcher. In the Format Picture dialog box, in the left pane, click 3-D Format, and then in the 3-D Format pane, under Bevel, in the Top section, do the following: Click the button next to Top and then select Convex (second row, third from the left) In the Width box, enter 6 pt. In the Height box, enter 6 pt. Also in the Format Shape dialog box, in the left pane, click Line Color, and then in the Line Color pane, do the following: Click Solid line. Click the button next to Color, and then click More Colors. In the Colors dialog box, on the Custom tab, enter Red: 8, Green: 18, Blue: 31. Also in the Format Shape dialog box, in the left pane, click Line Style, and then in the Line Style pane, in Width box, enter 0.75 pt. To reproduce two additional pictures and the cube, do the following: Select the picture on the slide. On the Home tab, in the Clipboard group, click the arrow next to Copy, and then click Duplicate. Repeat this step again for a total of three pictures. Position the pictures on the slide so that each one is visible. Select one of the duplicate pictures. Under Picture Tools, on the Format tab, in the Adjust group, click Change Picture. In the Insert Picture dialog box, select a picture, and then click Insert. Select the picture. Under Picture Tools, on the Format tab, in the Size group, click the Size and Position dialog box launcher. In the Format Picture dialog box, resize or crop the image so that the height is set to 3.42โ and the width is set to 3.42โ. To crop the picture, click Crop in the left pane, and in the Crop pane, under Crop position, enter values into the Height, Width, Left, and Top boxes. To resize the picture, click Size in the left pane, and in the right pane, under Size and rotate, enter values into the Height and Width boxes. Repeat steps 1 -3 to reproduce another picture. Select the picture that will appear on the top of the cube. Under Picture Tools, on the Format tab, in the Picture Styles group, click Picture Effects, point to 3-D Rotation, and then under Parallel, click Off Axis 1 Top (second row, third option from the left). Select the picture that will appear on the left side of the cube. Under Picture Tools, on the Format tab, in the Picture Styles group, click Picture Effects, point to 3-D Rotation, and then under Parallel, click Off Axis 1 Left (second row, first option from the left). Select the picture that will appear on the right side of the cube. Under Picture Tools, on the Format tab, in the Picture Styles group, click Picture Effects, point to 3-D Rotation, and then under Parallel, click Off Axis 1 Right (second row, second option from the left). Drag the pictures on the slide to create a cube. The edges of each picture may not line up exactly. To align the pictures as closely as possible, on the View tab, click Zoom. In the Zoom dialog box, click 400%, and then drag the pictures on the slide. Tip: To help more precisely place the pictures, select the picture that you want to move, then hold down the CTRL key and use the keyboard direction arrow keys. Press and hold SHIFT and select all three pictures on the slide. On the Home tab, in the Drawing group, click Arrange, and then click Group. On the Home tab, in the Editing group, click Select, and then click Selection Pane. Edit the name of the group in the Selection and Visibility pane, by double-clicking the group and then entering Cube Group. To reproduce the shadow effects on this slide, do the following: On the Home tab, in the Drawing group, click Shapes, and then under Rectangles click Rectangle (first option from the left). On the slide, drag to draw a rectangle. Select the rectangle. Under Drawing Tools, on the Format tab, in the Size group, do the following: In the Shape Height box, enter 3.42โ. In the Shape Width box, enter 3.42โ. On the Home tab, in the Drawing group, click the arrow next to Shape Fill, and then under Theme Colors click White, Text 1 (first row, second option from the left). On the Home tab, in the Drawing group, click the arrow next to Shape Outline, and then click No Outline. On the Home tab, in the bottom right corner of the Drawing group, click the Format Shape dialog box launcher. In the Format Shape dialog box, click 3-D Rotation in the left pane. In the 3-D Rotation pane, click the button next to Presets, and then under Parallel click Off Axis 1 Top (second row, third option from the left). Also in the Format Shape dialog box, click Shadow in the left pane, and then do the following in the Shadow pane: Click the button next to Presets, and then under Perspective click Below (first row, third option from the left). In the Transparency box, enter 72%. In the Size box, enter 110%. In the Blur box, enter 41 pt. In the Angle box, enter 115ยฐ. In the Distance box, enter 111 pt. On the Home tab, in the Drawing group, click Arrange, and then click Send to Back. Drag the rectangle under the cube so that it looks like the cube is floating. On the Home tab, in the Editing group, click Select, and then click Selection Pane. In the Selection and Visibility pane, press and hold CTRL and select both Cube Group and the rectangle. On the Home tab, in the Drawing group, click Arrange, and then do the following: Click Group. Point to Align, and then click Align to Slide. Point to Align, and then click Align Center. Point to Align, and then click Align Middle. To reproduce the animation effects on this slide, do the following: Select the cube. On the Home tab, in the Drawing group, Clipboard group, click the arrow next to Copy, and then click Duplicate. Click one of the pictures in the new group of pictures and under Picture Tools, on the Format tab, in the group, click Change Picture. In the Insert Picture dialog box, select another picture and click Insert. If necessary resize the picture โ under Picture Tools, on the Format tab, in the Size group, click the Size and Position dialog box launcher. In the Format Picture dialog box, resize or crop the image so that the height is set to 3.42โ and the width is set to 3.42โ. To crop the picture, click Crop in the left pane, and in the Crop pane, under Crop position, enter values into the Height, Width, Left, and Top boxes. To resize the picture, click Size in the left pane, and in the right pane, under Size and rotate, enter values into the Height and Width boxes. Right-click another picture in the new group of pictures and repeat step 2.Note: If necessary, reposition the new pictures so they form a cube. Select the second cube. On the Animations tab, in the Animations group gallery of animation effects, under Entrance, click Fade. In the Animation Pane, click the arrow next to the animation, and then click Timing. In the Fade dialog box, on the Timing tab, in the Delay box, enter 0.5 seconds, and then click OK. Select both cubes. On the Home tab, in the Drawing group, click the arrow below Arrange, and under Position Objects, point to Align, and do the following: Select Align Center. Select Align Middle. Repeat steps 1 through 6 two more times to reproduce the third and fourth cube, which improves the animation effect. To reproduce the background effects on this slide, do the following: On the Design tab, in the Background group, click Background Styles, and then select Style 8 (second row, fourth from the left). Note: If this action is taken in a PowerPoint presentation containing more than one slide, the background style will be applied to all of the slides.
- 2 DEFINlTIONS 2.1 International definitions Quality assurance. All those planned and systematic actions necessary to provide adequate confidence that a product or service will satisfjl given requirements for quality(lo). Trueness: closeness of the agreement between the average value obtained from a large series of test results and an accepted reference value(11). Precision: closeness of agreement between independent test results obtained under prescribed conditions(l2). Bias: difference between the expectation of the test results and an accepted reference value(ll). Accuracy: closeness of the agreement between the result of a measurement and a true value of the measurand(l3). Note 1. Accuracy is a qualitative concept. Note 2. The termprecision should not be used for accuracy. Error: result of a measurement minus a true value of the measurand(13). Repeatability conditions. conditions where independent test results are obtained with the same method on identical test items in the same laboratory by the same operator using the same equipment within short intervals of time(11). Uncertainty of measurement: parameter, associated with the result of a measurement, that characterises the dispersion of the values that could reasonably be attributed to the measurand(l4). Note I. The parameter may be, for example, a standard deviation (or a given multiple of it), or the half-width of an interval having a stated level of confidence. Note 2. Uncertainty of measurement comprises, in general, many components. Some of these components may be evaluated from the statistical distribution of results of a series of measurements and can be characterised by experimental standard deviations. The other components, which can also be characterised by standard deviations, are evaluated from assumed probability distributions based on experience or other information. Note 3. It is understood that the result of a measurement is the best estimate of the value of a measurand, and that all components of uncertainty, including those arising from systematic effects, such as components associated with corrections and reference standards, contribute to the dispersion. Traceability: property of the result of a measurement or the value of a standard whereby it can be related to stated references, usually national or international standards, through an unbroken chain of comparisons all having stated uncertainties(13). 0 1995 IUPAC, Pure and Applied Chemistry, 67,4 654 WP ON HARMONIZATION OF QUALITY ASSURANCE SCHEMES FOR ANALYTICAL LABS Reference material: material or substance one of whose property values are sufficiently homogeneous and well established to be used for the calibration of an apparatus, the assessment of a measurement method, or for assigning values to materials(l3). Certified reference material: reference material, accompanied by a certificate, one or more of whose property values are certified by a procedure which establishes its traceability to an accurate realisation of the unit in which the property values are expressed, and for which each certified value is accompanied by an uncertainty at a stated level of confidence(l3).
- 2.1 International definitions Quality assurance. All those planned and systematic actions necessary to provide adequate confidence that a product or service will satisfjl given requirements for quality(lo). Trueness: closeness of the agreement between the average value obtained from a large series of test results and an accepted reference value(11). Precision: closeness of agreement between independent test results obtained under prescribed conditions(l2). Bias: difference between the expectation of the test results and an accepted reference value(ll). Accuracy: closeness of the agreement between the result of a measurement and a true value of the measurand(l3). Note 1. Accuracy is a qualitative concept. Note 2. The termprecision should not be used for accuracy. Error: result of a measurement minus a true value of the measurand(13). Repeatability conditions. conditions where independent test results are obtained with the same method on identical test items in the same laboratory by the same operator using the same equipment within short intervals of time(11). Uncertainty of measurement: parameter, associated with the result of a measurement, that characterises the dispersion of the values that could reasonably be attributed to the measurand(l4). Note I. The parameter may be, for example, a standard deviation (or a given multiple of it), or the half-width of an interval having a stated level of confidence. Note 2. Uncertainty of measurement comprises, in general, many components. Some of these components may be evaluated from the statistical distribution of results of a series of measurements and can be characterised by experimental standard deviations. The other components, which can also be characterised by standard deviations, are evaluated from assumed probability distributions based on experience or other information. Note 3. It is understood that the result of a measurement is the best estimate of the value of a measurand, and that all components of uncertainty, including those arising from systematic effects, such as components associated with corrections and reference standards, contribute to the dispersion. Traceability: property of the result of a measurement or the value of a standard whereby it can be related to stated references, usually national or international standards, through an unbroken chain of comparisons all having stated uncertainties(13). 0
- 2.2 Definitions of terms specific to this document Internal quality control: set of procedures undertaken by laboratory stafF for the continuous monitoring of operation and the results of measurements in order to decide whether results are reliable enough to be released. Control material: material used for the purposes of internal quality control and subjected to the same or part of the same measurement procedure as that used for test materials. Run (analytical run): set of measurements performed under repeatability conditions. Fitness for purpose: degree to which data produced by a measurement process enables a user to make technically and administratively correct decisions for a stated purpose Analytical system: range of circumstances that contribute to the quality of analytical data, including equipment, reagents, procedures, test materials, personnel, environment and quality assurance measures.
- The performance of a method routinely used in a laboratory must be monitored continuously by quality control techniques in order to detect any change in accuracy or precision and take corrective action. Quality control is of two kinds: internal quality control, the procedure making use of results of only one laboratory for quality control; and external quality control in which the results of several laboratories which analyse the same sample(s) are used.
- Two major types of errors may occur in a laboratory: Random errors that arise due to inadequate control on pre-analytical variables, patient identity, sample labelling, sample collection, handling and transport, measuring devices etc. Systemic errors that occur due to inadequate control on analytical variables; e.g. due to error in calibration, impure calibration material, unstable/ deteriorated calibrators, unstable reagent blanks etc. The performance of a method routinely used in a laboratory must be monitored continuously by quality control techniques in order to detect any change in accuracy or precision and take corrective action. Quality control is of two kinds: internal quality control, the procedure making use of results of only one laboratory for quality control; and external quality control in which the results of several laboratories which analyse the same sample(s) are used.
- It is very difficult to establish effective methods for monitoring and controlling preanalytical variables because may of the variables are outside the laboratory areas. ย Requires the coordinated effort of many individuals and hospital departments
- CONTROL OF THE ANALYTICAL QUALITY USING STABLE CONTROL MATERIALS The performance of analytical methods can be monitored by analyzing specimens whose concentrations are known and then by comparing the observed values with known values. The known values are usually represented by an interval of acceptable values, or upper and lower limits for control (control limits) When the observed values fall within the control limits โ analysis is working properly When the observed value fall outside the control limits the analyst should be alerted to the possibility of problems in the analysis. A control also has a known amount of an analyte but is used to monitor the precision and accuracy of an assay method once it has been calibrated. Use 2 or three levels of controls Include with patient samples when performing a test Used to validate reliability of the test system Types of Control Materials Assayed mean calculated by the manufacturer must verify in the laboratory Un-assayed less expensive must perform data analysis โHome madeโ or โIn-houseโ pooled sera collected in the laboratory characterized preserved in small quantities for daily use
- External QC programme: The concerned laboratory is provided with vials of controls without reference values for analysis under the conditions of that lab. The results obtained would be sent to the reference laboratory for verification. Internal QC programme is suitable to determine the reproducibility of result (precision). External QC programme is useful to assess the closeness of a result to the actual value (accuracy). If the result of the presently used method widely deviates from the majority of the other methods which agree with one another, the method should be immediately replaced by another. Revaluation of calibration standards, reagents, pipettes and measuring devices must be considered in case of any kind of deterioration.
- Internal quality control (QC) programme may be formulated considering the following points: 1. Clinical correlation of test with the disease the patient is suspected to be suffering from. 2. Within-assay variation: The same sample is analysed twice during an assay and the outcome noted. Results should be identical if no error exists; a large variation suggesting one or more errors. 3. Intra-laboratory duplicates: Samples may be analysed in duplicates for 2 days and reproducibility of the four values checked. 4. The results of a test may be compared with the results of the same tests previously conducted on the patient. The values are expected to increase with disease progression and vice versa. A deviation from this pattern indicates error.