QC manual.pdf

 What is Quality Control?  Quality Control Products  Internal Quality Control  Why do we need Internal Quality Control?  Aim of IQC  Types of Control sera (IQC)  Carry Over  Duplicated measuring  Measuring of Impression  Measuring of Precision  Pooled Sera (Levy Jennings Chart)  Co...

 What is Quality Control?  Quality Control Products  Internal Quality Control  Why do we need Internal Quality Control?  Aim of IQC  Types of Control sera (IQC)  Carry Over  Duplicated measuring  Measuring of Impression  Measuring of Precision  Pooled Sera (Levy Jennings Chart)  Commercially prepared control sera  Impression (Acceptable limit)  Impression %  Impression & precision % 1  The precision of the method. (Error caused by substances)  The accuracy of the method. (Recovery Test)  The sensitivity of the method. (Detection limit)  The specificity of the method. (Measure only analyte of interest)  The linearity of the method. (Concentration range)  Assessment 2 Student Name…………………………………….. University No:………………………… Teaching Staff of Clinical Chemistry Department: Dr. Mohammed Hilal Dr. Alrashed Abrahim Dr. Zuhair Yagoub Astuz: Suzan Osman Astuz: Sara Alrashed Astuz: Wiaam Alser Astuz: Salma Baheir Astuz: Nada Mahmoud Astuz: Hassan Ahmed Astuz: Hafya AbuAlmakarm L.T: Ayman Seid Ahamed This manual Prepared by: Dr. Zuhair Yagoub Abdelkarim 3  Laboratory Quality Control Workbook Overview Learn how to calculate the required and other useful statistics Learn how to recognize patterns in quality control data that may indicate the test system is operating outside of specifications Learn how to investigate and troubleshoot when certain patterns exist Discover important items to consider when purchasing a control product What You Will Learn? Define and apply the basic elements of quality control, and implement a quality control program in the laboratory Define, calculate and apply the following statistics: mean, standard deviation, coefficient of variation, coefficient of variation ratio and standard deviation index Describe, choose and apply each of the Westgard rules Identify which Westgard rules identify random error and which rules identify systematic error Identify and differentiate trend and shift Identify and differentiate random error and systematic error 4  Construct a Levey-Jennings chart and evaluate graphed data for out of control events Assess instruments, reagents, and control products using the coefficient of variation Evaluate within lab precision using the coefficient of variation ratio Evaluate laboratory accuracy using the standard deviation index Choose and/or recommend control materials based on shelf life, box pricing, clinically relevant decision levels, matrix effects and inter laboratory comparison programs What is Quality Control? Quality control in the medical laboratory is a statistical process used to monitor and evaluate the analytical process that produces patient results. QC results are used to validate whether the instrument is operating within predefined specifications, inferring that patient test results are reliable. Once the test system is validated, patient results can then be used for diagnosis, prognosis, or treatment planning. Quality Control Products A quality control product is a patient-like material ideally made from human serum, urine or spinal fluid. A control product can be a liquid or freeze dried (lyophilized) material and is composed of one or more constituents (analytes) of known concentration. Control products should be tested in the same manner as patient samples. A quality control product usually contains many different analytes. For example, a general chemistry control can contain any number of chemistry analytes including potassium, glucose, albumin and calcium. 5 A normal control product contains normal levels for the analyte being tested. An abnormal control product contains the analyte at a concentration above or below the normal range for the analyte. For example, the normal range for a potassium level is about 3.5 – 5.0 mmol/L. A normal control would contain potassium at a level within this range. An abnormal control would contain potassium at a level below 3.5 mmol/L or above 5.0 mmol/L. Regular Testing Good laboratory practice requires testing normal and abnormal controls for each test at least daily to monitor the analytical process. Self- Test 1. What is quality control? 2. Name two components of quality control in the medical laboratory? 3. What is mmol/L? 4. How often should quality control products be tested? 5. If the QC result for the normal level of control is outside the range defined for that control level, normal patient results may be reported. (Circle the answer below) o True o False Internal Quality Control 6 Done during the day routine work, provides an immediate control. Errors are corrected immediately. Why do we need Internal Quality Control? 1. Monitor analytical processes. 2. Detect analytical errors. 3. Prevent reporting of incorrect patient values. 4. To ensure that test results are reliable. Aim of IQC: Is to monitor the analytical method and detection of any deviation during the analysis Types of Control sera (IQC) 1- Carry over. 2- Pooled Sera. 3- Commercially prepared control sera. I. - Freeze dried (Lyophilized sera). II. - Liquid synthetically manufactured sera. 4- Duplicated test on patient specimen. (Runs at the same time, differences between duplicate should not exceed 2SD). Practical No ( ) 7 Date............. Internal Quality Control Carry Over. Glucose Estimation Enzymatic colorimetric method Aim To determine the blood glucose concentration in blood sample. Principle: Beta-D- GLUCOSE + H2O + O2 ----GOD-----→ D- GLUCONATE +H2O2 4-A.A + PHENOL + H2O2 ---POD-----→ quinoneimine +H2O REAGENT: 1. Mono reagent: phosphate buffer 100 mmol\l, PH 7.5, glucose oxidase > 10 u/l, peroxidase >1 u/l, 4-aminoantipyrine 0.4 mmol/l, phenol 5 mmol\l. 2. Glucose standard: 100 mg\dl Sample: Serum or fluoride oxalate plasma free of hemolysis. Reagent and stander stable until expiry date when store at 2-8 Co Procedure: Blank STD Test QC sample Working reagent 1000 µL 1000 µL 1000 µL 1000 µL STD 100mg/dl ----- 10 µL ------- Sample ------- ------ 10 µL QC sample 10 µL Mix well; incubate for 10 min at R.T, read the absorbance of test and std against reagent blank using 520 nm (green) filter. Calculation: 8 O.D of test / O.D of STD × conc of STD = conc. Of test (mg\dl) QC sample: ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… …………………………………………………………………………………… Patient sample ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………. Comment:…………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ………………………………………………………………………. Practical No ( ) 9 Date............. Internal Quality Control Measuring of Impression  Error of scatter  Determine of impression by: 1) Duplicated Analysis (difference > SD ) 2) CV % 3) Levey Jennings Chart (+ 2SD) 4) Acceptable limit 5) Impression % 1) Duplicated measuring (difference > SD ) AIM : To study the random error (imprecision) PROCEDURE: Estimate the concentration of the analytes in the controls &in the sample (2times) C1&C2. C1 C1 C2 C2 Test1 Test2 STD Blank Glucose reagent 1ml 1ml 1ml 1ml 1ml 1ml 1ml 1ml Control1 0.01ml 0.01ml Control2 0.01ml 0.01ml Sample 0.01ml 0.01ml Glucose STD 0.01ml Mix incubates for 10 min at RT. Read the absorbance of the test controls and STD against blank at 510 nm.  Calculate the different between the 2 concentrations of control (d). 10   Obtain the square different of the concentrations (d2) for the controls.  Obtain the summation of d2. (Ʃd2). For controls Con1 Con2 d d2 C1 C2 3 C-- C10 Ʃ  Calculate the mean & standard deviation using the following formula X X=∑ N √∑ 2 = 2  Obtain the 2SD.  Calculate (d) for the sample  Reported or Rejected of sample result : If the d of the sample is < 2SD the result is reported. If the d of the sample is > 2SD the result is 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Internal Quality Control Measuring of precision  Relative standard deviation index (CV %):  The CV % should be less than 5 % for precise measuring.  The confident interval of QC is defined as the QC acceptable limit + 2 SD (95%) for the run of QC. You are provided with glucose control liquid sera. Replicated the control sera for glucose measuring 20 times and calculate:  Mean(X)  The confident interval (control rang)  Relative standard deviation index (CV %) 13 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Practical No ( ) 15 Date............. Internal Quality Control How to construct Levy Jennings Chart Using Pooled Sera Levey-Jennings Charts To simplify the review of quality control data, most clinical laboratories plot them on a Levey-Jennings chart, which is a graphical representation of the results over a certain period of time. Typical Levey-Jennings chart. All results for 20 consecutive runs are within 2 SD of the mean (x + 2s). Usually by established by analyzing control sera (pooled sera) at least 20 times You are provided with Pooled serum collected from 100 normal individuals (without sings & symptoms of dieses, No metabolic disorders & others disorders), 16 Cholesterol STD (200 mg/dl). Replicated measuring the Pooled serum for total cholesterol at least 20 times.  Construct Levey Jennings Chart for Cholesterol Estimations.  Use the westgard multirules (Accept or rejects) for QC sample run ( day 15 )  Use the QC result (Accept or Reject) for patient sample. 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Practical No ( ) 19  Date............. Internal Quality Control Commercially prepared control sera. Liquid synthetically manufactured sera The Assayed control Sera: (have determined range of values) analytes Methods Mean Range( +2SD) Glucose Glucose oxidase/peroxidase 100 85 - 115 Uric Acid Uricase enzyme 5.5 4.5 – 6.5 Creatinine Jaffe-kinetic 1.1 0.5 – 1.7 Urea Urease enzyme 35 25 - 45 You are provided with uric acid reagent (Uricase enzyme method) & uric acid STD = 6 mg/dl, estimate the patients sample A, B, C for uric acid concentrations. By using the commercial liquid assayed control sera: I. Construct Levey Jennings Chart for Uric Acid estimations. II. Using the westgard- multi- rules for the Accept or Reject run for A &B patients’ samples. For day 2 if QC result = 4.5 mg/dl III. Using the westgard- multi- rules for the Accept or Reject run for C patient sample. For day 3 if QC result = 6.5 mg/dl. 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Practical No ( ) 22 Date............. Internal Quality Control Impression Acceptable limit  Lower Accepted Limit (L.A.L)  Upper Accepted Limit (U.A.L)  Lower Accepted Limit (L.A.L) = Lower limit+ truncation Truncation = lower limit × C V% 100  Upper Accepted Limit (U.A.L) = Upper limit+ truncation Truncation = upper limit × C V% 100 You are provided with QC sample for glucose estimation using the glucose STD=100 mg/dl & glucose reagent for estimation (10 times). Calculate the:  SD  CV%  Acceptable limit  Comment on your result.............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................. 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25 Practical No ( ) Date............. Internal Quality Control Impression %  Precision from LJ chart = Mean + 2 SD  SD = allowable imprecision × Mean = (5× Mean) 100 100  Precision > allowable SD  Precision % = 100 – imprecision.  Imprecision from replicated control sera = CV %  Precision % = 100 – CV%  Precision < 95%.  Duplicated measurements imprecision = Difference in two Conc × 100 Mean of two Conc You are provided with Bruit reagent & control sera for protein estimations the control sera label (A), (B) and protein STD= 0.065 g/ml find the following: I. Duplicated control sera labelled (A) & Calculate Precision %. II. Replicated control sera labelled (B) 8 times & Calculate Precision %b& Acceptable limits III. Comment in your results 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29 Practical No ( ) Date............. Internal Quality Control Impression & precision %  Precision from LJ chart = Mean + 2 SD  SD = allowable imprecision × Mean = (5× Mean) 100 100  Precision > allowable SD  Precision % = 100 – imprecision.  Imprecision from replicated control sera = CV %  Precision % = 100 – CV%  Precision < 95%.  Duplicated measurements imprecision = Difference in two Conc × 100 Mean  Replicated = CV% = SD × 100 Mean 3 Patient specimens requested for uric acid estimation. Duplicated the 3 specimens labelled (1), (2) & (3)if you are provided with uric acid reagent & uric acid STD = 0.357 mmol/L, fined the following: I. Calculate SD for different specimens, and comment on your result according to 2SD either repeated or reported of the results II. Calculate the Precision % & imprecision for duplicated specimens (1) & (2) 30 Remember that the precision statistics:- 2  SD duplicated = √∑ 2 √ ∑ − 2  SD replicated = = N X  Mean : X = ∑ 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33 HOW TO VALIDATE A NEW METHOD  Before a new method is validated for use the following should be determined; 1) The precision of the method. 2) The accuracy of the method. 3) The sensitivity of the method. 4) The specificity of the method. 5) The linearity of the method.  What is accuracy? This can be defined as the agreement between the measured value and true value.  How to determine the accuracy of the method? This can be determined by many ways; A. Comparison method B. Using control sera C. Recovery method D. Interference method 1- PERCISION OF THE METHOD  What is precision? This can be defined as the agreement between repeated value. 34   How to determine the precision? This is done by repeat runs to check that results are reproducible from batch to batch or from day to day. Example; duplicate analysis 35 Practical No ( ) Date............. Internal Quality Control RECOVERY STUDIES METHOD Recovery Test  This is used so as to known whether a method measures all of the analyte or only part of it.  Recovery defines as a percentage different from the value of 100%.  Method; a test sample is prepared by adding small amount of concentration of the analyte in diluents to the patient sample.  Another sample is prepared from the patient specimen by diluting it with the same volume, but containing only the diluents.  Both diluted specimen are then analyzed by the test method.  The amount recovered is the difference between the measured values of the 2 samples.  The concentration recovered = (conc. Added) – (diluted test)  Recovery(%) = conc. Recovered x100 original Conc  Proportional error = 100 – (recovery %)  If the proportional error is less than the allowable error, then the method is acceptable. Recovery specimen: 0.1 STD+ 0.9 specimens - Specimen original : 0.9 ml specimen - Additive concentration: volume of recovery STD × Conc of STD Initial volume Additive Conc =0.1 \1 ×100 = 1/10 ×100 = 10 mg/dl. 36   Calculation of recovery concentration = Mean of recovery specimen – mean of patient specimen  Recovery % = Recovery Conc ×100 Additional Conc  If recovery is < 90% the method is acceptable  If recovery is > 90% the method is 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38 Practical No ( ) Date............. Internal Quality Control INTERFERANCE STUDIES METHOD  This is used to measure systematic error caused by substances other than the analyte which cause these errors either by react with analytical reagent or alter the reaction between the analyte and analytical reagent.  This method is similar to recovery except that the substance suspected of interference is added to the patient sample.  Common interferences; hemoglobin, hemolysis, bilirubin lipids, anticoagulants, preservatives, turbidity.  Interference is minimized by using blank solution or what is called (test blank) to correct for other substance in the sample by adding the sample to the blank solution but without analytical reagent (reactive 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41 Practical No ( ) Date............. Internal Quality Control SENSITIVITY OF THE METHOD as image  The analytical sensitivity or detection limit refers to smallest concentration that can be measured accurately.  A professional group has defined the detection limits as equal to three times the standard deviation of the blank. Procedure:- 1st obtain the points using the formula: - 5points Z = A+D (N -1) where:- Z = FINAL CONC. A= FIRST CONC. D= DIFFERENT BETWEEN THE POINT. N= NUMBER OF POINTS. 2nd prepare the series of dilutions with different conc. using the formula: RV/O Where:- R= required conc. V= required volume. O= original conc. 3th , estimations of STDs and obtains O.D of each STDs. 4th , construct on graph paper the standard curve (CONC. Versus O.D). 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44  Conc O.D g/dl g/dl g/dl g/dl g/dl Using the data on the table to construct the curve 45 Practical No ( ) Date............. Internal Quality Control SPECIFICITY OF THE METHOD  Specificity refers to methods to measure only analyte of interest.  A method selected to measure for example glucose, should ideally be specific for glucose.  This method has an advantages over another nonspecific method which in addition to measuring the substance under investigation, measure other unwanted but similar substance........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................... 46..........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................