Module 5 Quality Control PDF

Evolve. Adapt. Overcome. CEFI is now ready. MODULE 5 / QUALITY CONTROL MLS 109: Clinical Chemistry 1 WILLIAM CHRISTOPHER C. SALAZAR, RMT College of Medical Technology ...

Evolve. Adapt. Overcome. CEFI is now ready. MODULE 5 / QUALITY CONTROL MLS 109: Clinical Chemistry 1 WILLIAM CHRISTOPHER C. SALAZAR, RMT College of Medical Technology  COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. QUALITY ASSURANCE A complete system of creating and following procedures and policies to aim for providing the most reliable patient laboratory results and to minimize errors in the pre analytical, analytical and post analytical phases. Monitors quality performance starting from the ordering of a laboratory determination to its reporting, the interpretation of results, and then application to patient care.  COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. QUALITY ASSURANCE Involves total quality control which requires constant attention of all involved with the process or system. Principle Every laboratory section must have a plan to address preanalytical, analytical and postanalytical testing. Personnel must be trained in every procedure they perform and they must be tested annually for competency.  COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. QUALITY ASSURANCE Procedure manuals, formatted according to CLSI standards, must be available for procedures and must be followed by personnel explicitly. Instrument maintenance and calibration procedures and documentation of the same must be in place. Problem log books should be used to identify potential problems and course of action implemented.  COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. QUALITY ASSURANCE Indicators should be identified to monitor potential problems, thresholds set and data collected. A quality control program using control material that resembles patient samples must be run exactly as the patients  COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. TERMINOLOGIES Sensitivity The ability of an analytical method to measure the smallest concentration of the analyte of interest. High sensitivity = none or low number of false negatives Specificity The ability of an analytical method to measure only the analyte of interest. High specificity = low number of false positives  COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. TERMINOLOGIES Accuracy The extent to which the mean measurement is close to the true value. Indicates how close to the true value the result is. Counterchecked using the mean  COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. TERMINOLOGIES Estimated using 3 types of studies Recovery Determines how much of the analyte can be identified in the sample Interference Determines if specific compounds affect the laboratory tests like hemolysis, turbidity, etc. Patient sample comparison Used to assess presence of error in actual patient sample  COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. TERMINOLOGIES Precision Indicates how close the values are to one another Counterchecked using COV Terms related to precision o Repeatability Closeness of agreement between results of successive instruments carried out under the same conditions  COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. TERMINOLOGIES Reproducibility Closeness of agreement between results of measurements performed under changed conditions of measurements. Reliability Ability of the analytical method to maintain accuracy and precision over an extended period of time. Practicability The degree to which a method is easily repeated.  COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. TERMINOLOGIES Diagnostic sensitivity  Is the ability of the analytical method to detect the proportion of individuals with the disease.  It indicates the ability of the test to generate more true-positive results and few false-negative  Screening tests require high sensitivity so that no case is missed  Sensitivity =  COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. TERMINOLOGIES Diagnostic specificity  Is the ability of the analytical method to detect the proportion of individuals without the disease  It reflect the ability of the method to detect true- negatives with very few false-positives  Confirmatory test requires high specificity to be certain of diagnosis  Specificity =  COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. TERMINOLOGIES Delta check  The current test value is compared to a previous value or values to detect large changes  COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. QUALITY CONTROL QC is concerned with the analytic phase of QA It is a process of ensuring that analytical results are correct by testing known samples that resembles patient samples. It involves the process of monitoring the characteristics of the analytical process and detects analytical errors during testing, and ultimately prevent the reporting of inaccurate patient test results.  COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. QUALITY CONTROL 2 Major Types of QC 1. Internal QC / Intra-Laboratory QC Involves analyses of control samples together with the patient specimens. Primarily monitors day to day performance of laboratory tests. It is important for the daily monitoring of accuracy and precision of analytical methods.  COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. QUALITY CONTROL 2 Major Types of QC 2. External QC / Inter-Laboratory QC Involves proficiency training programs that periodically provide samples of unknown concentration to participating clinical laboratories. It is important in maintaining long-term accuracy of the analytical methods.  COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. QUALITY CONTROL Objectives of Quality Control 1. To check the stability of the machine 2. To check the quality of reagents 3. To check technical / operator errors  COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. QUALITY CONTROL Control Solutions / QC Materials Solutions that are used to check the precision and accuracy of an analytical method. It should resemble the patient specimen and be run with the patients.  COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. QUALITY CONTROL Control Solutions / QC Materials Characteristics of ideal control solution Behaves like real sample Available to last a minimum of one year Should vary minimally in concentration and composition from vial to vial No communicable diseases  COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. ANALYTICAL ERRORS Errors encountered in the collection, preparation, and measurement of specimens including transcription and releasing of results  COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. ANALYTICAL ERRORS A. Random Error Error that occurs unpredictably Affects precision and is the basis for varying differences between repeated measurements  COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. ANALYTICAL ERRORS A. Random Error Examples Variations in technique Pipetting error Mislabeling of samples Improper aliquoting Environmental conditions Temperature and voltage fluctuation  COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. ANALYTICAL ERRORS B. Systematic Error Error that occurs predictably once a pattern of recognition is established. Problem is constant or predictable from day to day. Detected as either positive or negative bias  COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. ANALYTICAL ERRORS B. Systematic Error Trend Values increase or decrease for six consecutive days (crosses the mean) Cause : deterioration of reagents  COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Trend  COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. ANALYTICAL ERRORS B. Systematic Error Shift Values distribute themselves on one side or either side of the mean for six consecutive days (does not cross the mean) Cause : improper calibration of the instrument  COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Shift  COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. ANALYTICAL ERRORS B. Systematic Error Examples Calibration problems Deterioration of reagents and control materials Improper preparation of standards and controls Contaminated solutions Unstable and inadequate reagent blanks  Failing instrumentation Poorly written procedures  COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. ANALYTICAL ERRORS C. Allowable Error The quantity of error that will not negatively affect clinical decisions. Total error must be less than the allowable error to be considered acceptable.  COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. STATISTICS Mean Measure of central tendency associated with symmetrical or normal distribution Formula ∑𝑥 Where x ̅ 𝑛  mean  summation of x  total number of samples  COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. STATISTICS Medial Midpoint, 50th percentile The value that divides the observations into two groups, each containing equal numbers of observation.  COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. STATISTICS Mode The most frequently occurring value Used to describe data with two centers (bimodal) Range The simplest expression of distribution Difference between the highest and the lowest score in a data  COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. STATISTICS Standard Deviation Measure of dispersion of the values from the mean A measure of distribution range Most frequently used measure of variation  COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. STATISTICS Standard Deviation 𝑆𝐷= √ ∑¿¿¿ Formula In a normal distribution 1 SD = 68% of the total population 2 SD = 95% of the total population (maximum allowable SD) 3 SD = 99.7% of the total population  COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. STATISTICS Coefficient of variation Expresses SD as a percentage of mean value Used to determine precision Formula 𝑆𝐷 CoV = x̅  COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. STATISTICS Variance Standard deviation squared Measure of variability Difference between each value and the average of the data Formula Variance = (SD)2  COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. STATISTICS T test Used to determine whether there is a statistically significant difference between the means of two groups of data. F test Used to determine whether there is a statistically significant difference between the standard deviations of two groups of data  COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. QUALITY CONTROL CHARTS 1. Gaussian Curve (Bell-Shaped Curve)  Occurs when the data set can be accurately described by the SD and the Mean.  Obtained by plotting the values from multiple analyses of a sample  Population probability distribution, that is symmetric about the mean  Occurs when the data elements are centered around the mean with most elements close to the mean  Focuses on the distribution of errors from the analytical method rather than the values from a healthy or patient  COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. 1. Gaussian Curve (Bell-Shaped Curve)  COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. QUALITY CONTROL CHARTS 2. Cumulative Sum Graph (CUSUM)  Calculates the difference between QC results and the target means  Common method: V-mask  Identifies consistent bias problems; it requires computer implementation  This plot will give the earliest indication of systematic errors (trend) and can be used with the 13s rule  Very sensitive to small, persistent errors that commonly occur in the modern, low calibration-frequency analyzer  Rules are out of control when the slope exceeds 45° or a  COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. 2. Cumulative Sum Graph (CUSUM)  COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. QUALITY CONTROL CHARTS 3. Youden/Twin Plot  Interlab  Used to compare results obtained on a high and low control serum from different laboratories  It displays the result of the analyses by plotting the mean values for one specimen on the ordinate (y-axis) and the other specimen on the abscissa (x-axis)  COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. 3. Youden/Twin Plot  COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. QUALITY CONTROL CHARTS 4. Shewhart Levey-Jennings Chart  Most widely used QC chart in the clinical laboratory  It allows the laboratorians to apply multiple rules without the aid of a computer  It is a graphic representation of the acceptable limits of variations in the results of an analytical method  Easily identifies random and systematic errors  COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. 4. Shewhart Levey-Jennings Chart  COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. QUALITY CONTROL CHARTS Westgard Multirules Establishes a criteria whether an analytic process is out of control According to Westgard, the use of simple upper and lower control limits is not enough to identify analytical problems. The combination of the control values used in conjunction with a control chart has been called the Multirule Shewhart Plot  COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. QUALITY CONTROL CHARTS Rules I. Random error 12s 1 control value exceeds 2 SD Warning rule – accept the run 13s 1 control value exceeds 3 SD R4s The difference between 2 control values are equal to  COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. QUALITY CONTROL CHARTS Rules II. Systematic error 22s 2 consecutive control values are greater than +/- 2SD 41s 4 consecutive control values on one side of the mean 10x 10 consecutive control values on one side of the mean COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc.