Method Selection and Evaluation Method Selection and Evaluation D. Kefaya EL- Sayed Mohamed Prof. Of Clinical Pathology (Clinical Chemistry), Mansoura.

Slides:



Advertisements
Similar presentations
Calibration Techniques
Advertisements

Why do Q.A.? Physician’s Expectations Diagnosis Therapy Technology Physician’s Expectations Diagnosis Therapy Technology.
J M KUYL Department of Chemical Pathology NHLS Universitas & UFS
Quantitation of Methemoglobin
Result validation. Exercise 1 You’ve done an analysis to the best of your ability using the correct procedure. Is your answer correct? possibly, hopefully.
L MACKAY, N CRINIS, Q LAM, R SCOTT
Laboratory Quality Control
Week 2: Spectrophotometry Spectrophotometry Beer’s law Standard curve Dilution problems Quality control Control samples Levey-Jenning chart Shift and trend.
Quality Assurance.
Titremetric analysis Dr. Mohammad Khanfar. Concept of Titremetric analysis In general, we utilize certain property of a substance to be analyzed in order.
Internal Quality Control (QC) for Medical Laboratories: An introduction Dr. Otto Panagiotakis and Dr. Alexander Haliassos ESEAP – Greek Proficiency Testing.
MLAB 1335 Immunology/Serology Terry Kotrla
Tandem Mass Spectrometry Newborn Screening Quality Assurance and Control Instrument and Method Validation Gary Hoffman Wisconsin Newborn Screening Laboratory.
BOHB APCCB LABORATORY USE OF THE ABBOTT MEDISENSE METER FOR BETA-HYDROXYBUTYRATE MEASUREMENT. GRD Jones, A Screnci, P Graham Chemical Pathology,
Kyiv, TRAINING WORKSHOP ON PHARMACEUTICAL QUALITY, GOOD MANUFACTURING PRACTICE & BIOEQUIVALENCE Validation of Analytical Methods Used For Bioequivalence.
Chemometrics Method comparison
Method Comparison A method comparison is done when: A lab is considering performing an assay they have not performed previously or Performing an assay.
Unit #7 - Basic Quality Control for the Clinical Laboratory
Quality Assurance.
Quality Assessment 2 Quality Control.
Anura L. Jayewardene, PhD Drug Research Unit at the General SFGH, 1001 Potero Ave. Bldg 100, Rm 157 San Francisco, CA Phone: (415) FAX:
ABC of Quality Control A problem based approach RT ERASMUS NHLS / FACULTY OF HEALTH SCIENCES, UNIVERSITY OF STELLENBOSCH 20th July, 2007, Bela Bela.
The following minimum specified ranges should be considered: Drug substance or a finished (drug) product 80 to 120 % of the test concentration Content.
Quality WHAT IS QUALITY
Abnormal inhibitory activity problem ( ) – ( ) X100 = 120 (%) !? ( ) – ( ) X100 = -10 (%) !!??
Prof. of Clinical Chemistry, Mansoura University.
Quality Control Lecture 5
Choice of Methods and Instruments
Clinical Lab Dilutions MLT 241 Intro to Clinical Chemistry SLO IX. Calculate mathematical manipulations and problems for basic math, the metric system,
G Jones, M Roser Department of Chemical Pathology
Quality Assurance How do you know your results are correct? How confident are you?
1 Exercise 7: Accuracy and precision. 2 Origin of the error : Accuracy and precision Systematic (not random) –bias –impossible to be corrected  accuracy.
Serum biochemical parameters glucose assay Biochemistry Clinical practice CLS 432 Dr. Samah Kotb Lecturer of Biochemistry 2015.
QC/QA.
Application of Westgard multi rules in medical laboratories
Interferences. Matrix interference the matrix is the major component of the sample can affect the measured analyte response Response = constant x concentration.
Quality Control Internal QC External QC. -Monitors a test's method precision and analytical bias. -Preparation of quality control samples and their interpretation.
LECTURE 13 QUALITY ASSURANCE METHOD VALIDATION
 Remember Chemistry panel Quality Control:-  In a medical laboratory, it is a statistical process used to monitor and evaluate the analytical process.
 Routine viral diagnostics: indirect and direct detection of viruses. ◦ Indirect detection: serological tests; ◦ Direct detection:  Viral antigens;
By: EID ALATAWI Serial Dilution. Introduction: Many of the laboratory procedures involve the use of dilutions. It is important to understand the concept.
Chapter 1: The Nature of Analytical Chemistry
Diagnostic clinical chemistry
Quality Assessment.
One-Stage Quantitative
Quality is a Lousy Idea-
Unit #6 - Basic Quality Control for the Clinical Laboratory
CHOICE OF METHODS AND INSTRUMENTS
P.J. Showell1, E.A. Lynch1, H.D. Carr-Smith1, A.R. Bradwell2
INTERNAL QUALITY CONTROL
Preparation of Solutions
CHOICE OF METHODS AND INSTRUMENTS
Cerebrospinal Fluid (CSF) Analysis for total protein
Quality Assurance in the clinical laboratory
iCAP OES Analysis of Trace Elements in Hair
Laboratory Quality Control
Practical clinical chemistry
Quality is a Lousy Idea-
This teaching material has been made freely available by the KEMRI-Wellcome Trust (Kilifi, Kenya). You can freely download,
Exp#4 Cholesterol Quantitative determination of total cholesterol in serum /plasma by enzymatic color/endpoint method.
به نام خدا تضمين کيفيت در آزمايشگاه
Chapter 5 Quality Assurance and Calibration Methods
Choice of Methods and Instruments
Coagulation Factor Assays
Key to Mock TOACS. Key to Mock TOACS Station No 1 (Analytical Work) (STATIC) A scientist is working on an enzyme method with NADH as the indicator.
Method Selection and Evaluation
Introduction To Medical Technology
Quality Control Lecture 3
▪Internal quality control:
Quality Assessment The goal of laboratory analysis is to provide the accurate, reliable and timeliness result Quality assurance The overall program that.
Presentation transcript:

Method Selection and Evaluation Method Selection and Evaluation D. Kefaya EL- Sayed Mohamed Prof. Of Clinical Pathology (Clinical Chemistry), Mansoura University

Before a new test or methodogy is introduced into the laboratory. both managerial and techinal information must be compiled and carefully considered. The information should be collected from many different sources,including manufacturer sales representatives,colleagues,scientific presentations,and the scientific literature.

Linear range:

O.D O.D Glucose concentration (mg/dl)

Observed value True value RE SE TE µ X

Inaccuracy:  The difference between a measured value and its true value.  Is due to the presence of systematic analytical error (S.E.)  S.E. can be constant or proportional.

Test Values Test Values Constant E Ideal Proprtional E 0 30 Reference Values

Inaccuracy  Can be estimated from three studies: recovery. recovery. interference. interference. a comparison-of-methods study a comparison-of-methods study

Example of a recovery study Sample preparation Sample 1:2.0 ml serum ml H2O Sample 2:2.0 ml serum +0.1 ml 20 mg /dl calcium standard Sample 3:2.0 ml serum +0.1 ml 50 mg /dl calcium standard Concentration Concentration Calcium measured added Recovered Recovery Calcium measured added Recovered Recovery Sample mg/dl Sample mg/dl 0.95mg/dl 0.85mg/dl 89% Sample mg/dl 2.38mg/dl 2.29mg/dl 96%

Calculation of recovery Concentration added = standard concentration x Ml standard Ml standard + ml serum Ml standard + ml serum = 20 x 0.1 = 20x 1 = 20 = 0.95 (Sample2) = 20 x 0.1 = 20x 1 = 20 = 0.95 (Sample2) x x10 21 conc. recovered = conc. ( diluted test) – conc. ( baseline) = =0.85 = =0.85 recovery = Conc. Recovered = x100% recovery = Conc. Recovered = x100% Conc. added Conc. added = 0.85 x 100 = 89 % ( sample 2) = 0.85 x 100 = 89 % ( sample 2)

( b )Interference:  The interference experiment is used to measure systematic errors caused by substances other than the analyte

Interference: Interference:  An interfering material can cause systematic errors in one of two ways : The material itself may react with the analytical reagents. The material itself may react with the analytical reagents. Or it may alter the reaction between the analyte and the analytical reagents Or it may alter the reaction between the analyte and the analytical reagents

Interference: Interference:  The interference likes recovery except that the substance suspected of interference is added to the patient sample.  The concentration of the potentially interfering material should be in the maximally elevated range.  If an effect is observed its concentration should be lowered to discover the concentration at which test resultes are frist invalidated

Example of an Interference study Sample preparation Sample 1 : 1.0 ml serum ml H2O (base line) Sample 2 : 1.0 ml serum ml of 10 mg/dl magnesium standard Sample 3 : 1.0 ml serum ml of 20 mg/dl magnesium standard Calcium Measured Magnesium added Interference Calcium Measured Magnesium added Interference Sample mg/dl Sample mg/dl 0.91mg/dl 0.73mg/dl Sample mg/dl 1.81mg/dl 1.68mg/dl

Calculation of interference Concentration added = standard concentration x = 10x 0.1 = 10 = 0..91mg/dl (sample2) = 10x 0.1 = 10 = 0..91mg/dl (sample2) Interference = conc. ( diluted ) – conc. ( baseline) = – 9.8 =0.73 (sample2) = – 9.8 =0.73 (sample2) ml standard ml standard + ml serum

 Common interferences (eg., hemoglobin, lipids,bilirubin,anticoagulants preservatives, and so on)also should be tested.  Glick and Ryder have presented " interferographs " for various chemistry instruments – these are graphs relating analyte concentration measured versus interferent concentration

( C ) comparison – of methouds Experiment:  The best comparative method that can be used is the reference method, which is a method with negligible inaccuracy in comparison with its imprecision.

 Reference methods may be laborious and time- consuming Because most laboratories are not staffed and equipped to perform reference methods, the results of the test method are usually compared with those of the method routinely in use.

 Westgard et al27 and the NCCLS35 recommend that at least 40 sample and preferably 100 samples, be run by botli methods. span the clinical range span the clinical range represent many different pathologic conditions. represent many different pathologic conditions. Duplicate analyses of each sample by each method. Duplicate analyses of each sample by each method.

 If 40 specimens are compared, two to five patient specimens should be analyzed daily for a minimum of 8 days.  If 100 specimens are compared the comparison study should be carried out during the 20-day replication study.

Test method Test method Reference Regression line

Example of Method selection and evaluation (Glucose in Serum)  Analytical Needs :- Rapid procedure is needed at time out side the regular working hours. Rapid procedure is needed at time out side the regular working hours. Sample Volume of 0.2 ml or less Sample Volume of 0.2 ml or less Analytical range of 0.0 to mg/dl. Analytical range of 0.0 to mg/dl. Turn arround time 30 min.or less is needed Turn arround time 30 min.or less is needed

 Quality goals:- The medical decision levels of interest are: 50 (hypoglycemia) 50 (hypoglycemia) 200 mg/dl (hyperglycemia) 200 mg/dl (hyperglycemia) The decision level for screening is 140mg/dl is not needed. The decision level for screening is 140mg/dl is not needed. Precision goals are 1.5 mg/dl at 50 mg/dl 5.0mg/dl at 200 mg/dl 5.0mg/dl at 200 mg/dl Total error goals (TEA) are 6.0 mg/dl at 50.0mg/dl 20.0mg/dl at mg/dl 20.0mg/dl at mg/dl

 Method selection :-  In kit form  Can be set up on an existing laboratory instrument  Requirements:-  Primary reference solutions are prepared for calibration  Control materials  Randomly selected clinical specimen.

 Within – Run Precision :  Analyze 20 aliquots of low abnormal control mean ±SD 56.5 mg/dl ± 0.7  Analyze 20 aliquots of moderatly high control mean ± SD ±2.1 mg/dl  SDs are less than the allowable error in non automated procedure.

 Day to Day precision:  Two Q.C pools are analyzed for 20 days mean ± SD  SD :1.5 mg /50 mg glucose 5.0 mg/200mg glucose 5.0 mg/200mg glucose

 Analytical Range :-  Glucose solutions prepared from a stock glucose reference solution of 1000mg/dl  Duplicate analyses  The plot shows excellent linearity to 600mg/dl. which meets the specification for linearity to 500mg/dl.  The absorbance at zero glucose concentration is the reagent blank value

O.D O.D Glucose concentration (mg/dl)

 Recovery:-  Two pooled sera are perpared as baseline specimens 61mg/dl,171mg/dl  concentrated glucose solution is prepared (10,000mg/dl)  two different amounts of glucose are added to 9.6 ml of pooled sera

171mg/dl61mg/dlTotal Nacl 0.15mol/l Glucese solution 10,000mg/dl bbbbbb aaaaaa 10.0mL 400.0ul 300.0ul 0.0ul 100.0ul 400.0ul Recovery:-

 Quadruplicate assays of A and B are performed and take the mean  Subtract the original (basal) glucose levels (61,171) from the mean of each quadruplicate Recovered glucose Recovered glucose  Recovery % =  Proportional error = 100- recovery% Recovered glucose Glucose added X100

Glucose Recovered mg/dl Glucose found Glucose added Pooled sera mg/dlml/10ml = AAABBBAAABBB Recovery:-

 Interference:  The potential interference of visible abnormal specimens is tested by: A analyzing a series of icteric, turbid,and hemolyzed sera using the new method and an established method know to be free of such interferenc

 The difference ( ) the two methods are 1 – 4 mg which is less than the allowable TEA. B add a small amount of highly concentrated solutions to pooled sera e.g. Ascorbic acid, sod. Salicylate, Trisodium citrate, Heparin, disod. EDTA. B add a small amount of highly concentrated solutions to pooled sera e.g. Ascorbic acid, sod. Salicylate, Trisodium citrate, Heparin, disod. EDTA.  The difference must be < TEA.

METHOD FOR GLUCOSEINTERFERENCE Test Comparative (mg/dl) Concentration Type ( Serum) 113±5.6 97± ± ± ±4.4 98± ± ± mg/dl 96mg/dl Turbid Normal Bil.(Icteric) Hb.(Hemo.) A 660 =0.45 Interference: