Quality-Control.ppt

Click to edit Master title style,Click to edit Master text styles,Second level,-Third level,Quality Control Introduction,Purchasing&Inventory,Assessment,Occurrence Management,Information Management,Process Improvement,Customer Service,Facilities&Safety,The Quality System,Organization,Personnel,Equipment,Documents&Records,Process Control (QC&EQA)&Specimen Management,The Quality Assurance Cycle,Pre-Analytic,Analytic,Post-Analytic,Data and Lab Management,Safety,Customer Service,Patient/Client Prep,Sample Collection,Sample Receipt and Accessioning,Sample Transport,Quality Control,Record Keeping,Reporting,Personnel Competency,Test Evaluations,Testing,Quality Control,Definitions,Qualitative Quality Control,Quantitative QC How to implement,Selection and managing control materials,Analysis of QC data,Monitoring quality control data,What is Quality Control?,Process or system for monitoring the quality of laboratory testing,and the accuracy and precision of results,Routinely collect and analyze data from every test run or procedure,Allows for immediate corrective action,Designing a QC Program,Establish written policies and procedures,Corrective action procedures,Train all staff,Design forms,Assure complete documentation and review,Qualitative vs.Quantitative,Quantitative test,measures the amount of a substance present,Qualitative test,determines whether the substance being tested for is present or absent,Qualitative QC,Quality control is performed for both,system is somewhat different,Controls available,Blood Bank/Serology/Micro,RPR/TPHA,Dipstick technology,Pregnancy,Stains,Reagents,Antisera,Label containers,contents,concentration,date prepared,placed in service,expiration date/shelf life,preparer,Media Preparation,Record amount prepared,Source,Lot number,Sterilization methodPreparation date,Preparer,pH,Expiration date,Microbiology QC,Check:,Sterility,Ability to support growth,Selective or inhibitory characteristics of the medium,Biochemical response,Frequency,Test QC organisms with each new batch or lot number,Check for growth of fastidious organisms on media of choice incubate at time and temp recommended,RECORD Results on Media QC form,Quality Control:Stains and Reagents,Gram stain QC,Use gram positive and gram negative organisms to check stain daily,Other:,Check as used positive and negative reactions,Stock QC organisms,Organisms to be maintained must be adequate to check all media and test systems.,E.coli,MacConkey,EMB,susceptibility tests,Staphylococcus aureus,Blood agar,Mannitol Salt,susceptibility tests,Neisseria gonorrhoeae,chocolate,Martin-Lewis,Detecting Errors,Many organisms have predictable antimicrobial test results,Staphylococcus,spp.are usually susceptible to vancomycin,Streptococcus pyogenes,are always susceptible to penicillin,Klebsiella pneumoniae,are resistant to ampicillin,Sources of Error,If you encounter an unusual pattern,rule out error by checking identification of organisms,repeat antimicrobial susceptibility test,Report if repeat testing yields same result,or refer the isolate to a reference laboratory for confirmation,Quality Control Quantitative Tests,How to implement a laboratory quality control program,Implementing a QC Program Quantitative Tests,Select high quality controls,Collect,at least,20 control values over a period of 20-30,days for each level of control,Perform statistical analysis,Develop Levey-Jennings chart,Monitor control values using the Levey-Jennings chart and/or Westgard rules,Take immediate corrective action,if needed,Record actions taken,Selecting Control MaterialsCalibrators,Has a known concentration of the substance(analyte)being measured,Used to adjust instrument,kit,test system in order to standardize the assay,Sometimes called a standard,although usually not a true standard,This is,not,a control,Selecting Control Materials Controls,Known concentration of the analyte,Use 2 or three levels of controls,Include with patient samples when performing a test,Used to validate reliability of the test system,Control MaterialsImportant Characteristics,Values cover medical decision points,Similar to the test specimen(matrix),Available in large quantity,Stored in small aliquots,Ideally,should last for at least 1 year,Often use biological material,consider bio-hazardous,Managing Control Materials,Sufficient material from same lot number or serum pool for one years testing,May be frozen,freeze-dried,or chemically preserved,Requires very accurate reconstitution if this step is necessary,Always store as recommended by manufacturer,Sources of QC Samples,Appropriate diagnostic sample,Obtained from:,Another laboratory,EQA provider,Commercial product,Types of Control Materials,Assayed,mean calculated by the manufacturer,must verify in the laboratory,Unassayed,less expensive,must perform data analysis,“Homemade”or“In-house”,pooled sera collected in the laboratory,characterized,preserved in small quantities for daily use,Preparing In-House Controls,Criteria for Developing Quality Controls for HIV,Low positive,Between the cut off and positive control,At a level where variability can be followed,Generally 2 times the cut off,Production of a QC Sample-Production Protocol,Materials,Calculation of Volume,stock sample,diluent,QC batch,Method,Validation Acceptance Criteria,batch,stability,Process for Preparing In-house Controls,Serial dilution of high positive stock sample,Select suitable dilution,Produce large batch,Test stability,Test batch variation,Dispense,label,store,Making Suitable Dilutions,100 ul serum,in tube 1,100ul diluent in each tube,Mix and Transfer,Each tube is a 1:2 dilution,of the previous tube,Discard,Selecting a Suitable Sample Dilution,Serial Dilutions on Abbott AxSYM HIV-1/HIV-2 MEIA,Doubling Dilutions,2,4,8,16,32,64,128,256,512,1024,2048,4096,8192,16384,32768,65536,131072,262144,524288,S/Co Ratio,0,2,4,6,8,10,12,14,16,18,20,Pos Cont 3.3,Neg Cont 0.38,Cut Off 1.0,Batch Production,Prepare positive sample,centrifuge,heat inactivate,Mix positive sample in diluent,magnetic stirrer,Bottle batch in numbered lots of suitable volume,Stability Testing,Assess the rate of deterioration,QC Sample,Storage,Day 7,Day 14,Day 21,Day 28,-20c,4c,16-25C,Batch Validation,Dispense aliquots,Test aliquots,Confirm desired titre level,compare against target value,Confirm minimal batch variation,acceptable if CV 20%,aim for 10%,Storage of QC Samples,Validated batch aliquoted into smaller user friendly volumes for storage,Establish a storage protocol:,store at-20,o,C,in use vials stored at 4,o,C,use 0.5 ml vial maximum of one week,freeze-dried,(requires accurate reconstitution),chemically preserved,Quality Control-Quantitative,Analysis of QC Data,How to carry out this analysis?,Need tools for data management and analysis,Basic statistics skills,Manual methods,Graph paper,Calculator,Computer helpful,Spreadsheet,Important skills for laboratory personnel,Analysis of Control Materials,Need data set of at least 20 points,obtained over a 30 day period,Calculate mean,standard deviation,coefficient of variation;determine target ranges,Develop Levey-Jennings charts,plot results,Establishing Control Ranges,Select appropriate controls,Assay them repeatedly over time,at least 20 data points,Make sure any procedural variation is represented:,different operators,different times of day,Determine the degree of variability in the data to establish acceptable range,Measurement of Variability,A certain amount of variability will naturally occur when a control is tested repeatedly.,Variability is affected by operator technique,environmental conditions,and the performance characteristics of the assay method.,The goal is to differentiate between variability due to chance from that due to error.,Measures of Central Tendency,Data are frequently distributed about a central value or a central location,There are several terms to describe that central location,or the central tendency of a set of data,Measures of Central Tendency,Median,=the value at the center(midpoint)of the observations,Mode,=the value which occurs with the greatest frequency,Mean,=the calculated average of the values,Calculation of Mean,X=Mean,X,1,=First result,X,2,=Second result,X,n,=Last result in series,n Total number of results,Calculation of Mean:Outliers,192 mg/dL,194 mg/dL,196 mg/dL,196 mg/dL,160 mg/dL,196 mg/dL,200 mg/dL,200 mg/dL,202 mg/dL,255 mg/dL,204 mg/dL,208 mg/dL,212 mg/dL,Calculation of Mean,192 mg/dL,194 mg/dL,196 mg/dL,196 mg/dL,196 mg/dL,200 mg/dL,200 mg/dL,202 mg/dL,204 mg/dL,208 mg/dL,212 mg/dL,Sum=2,200 mg/dL,Mean,=the calculated average of the values,The sum of the values(X,1,+X,2,+X,3,X,11,)divided by the number(n)of observations,The mean of these 11 observations is(2200,11)=,200 mg/dL,Calculation of Mean:ELISA Tests,Collect optical density(OD)values for controls for each assay run,Collect cutoff (CO)value for each run,Calculate ratio of OD to CO(OD/CO)for each data point or observation,This ratio standardizes data,Use these ratio values to calculate the mean,Normal Distribution,All values are symmetrically distributed around the mean,Characteristic“bell-shaped”curve,Assumed for all quality control statistics,Normal Distribution,Frequency,4.74.84.9Mean5.15.25.3,Normal Distribution,Mean,Accuracy and Precision,The degree of fluctuation in the measurements is indicative of the“precision”of the assay.,The closeness of measurements to the true value is indicative of the“accuracy”of the assay.,Quality Control is used to monitor both the precision and the accuracy of the assay in order to provide reliable results.,Precise and inaccurate,Precise and accurate,Precision and Accuracy,Imprecise and inaccurate,Measures of Dispersion or Variability,There are several terms that describe the dispersion or variability of the data around the mean:,Range,Variance,Standard Deviation,Coefficient of Variation,Range,Range refers to the difference or spread between the highest and lowest observations.,It is the simplest measure of dispersion.,It makes no assumption about the shape of the distribution or the central tendency of the data.,Calculation of Variance(S,2,),Calculation of Variance,Variance is a measure of variability about the mean.,It is calculated as the average squared deviation from the mean.,the sum of the deviations from the mean,squared,divided by the number of observations(corrected for degrees of freedom),Degrees of Freedom,Represents the number of independent data points that are contained in a data set.,The mean is calculated first,so the variance calculation has lost one degree of freedom(n-1),Calculation of Standard Deviation,Calculation of Standard Deviation,The standard deviation(SD)is the square root of the variance,it is the square root of the average squared deviation from the mean,SD is commonly used(rather than the variance)since it has the same units as the mean and the original observations,SD is the principle calculation used in the laboratory to measure dispersion of a group of values around a mean,Standard Deviation and Probability,For a set of data with a normal distribution,a value will fall within a range of:,+/-1 SD 68.2%of the time,+/-2 SD 95.5%of the time,+/-3 SD 99.7%of the time,68.2%,95.5%,99.7%,Frequency,-3s-2s -1s Mean +1s +2s+3s,Standard Deviation and Probability,In general,laboratories use the+/-2 SD criteria for the limits of the acceptable range for a test,When the QC measurement falls within that range,there is 95.5%confidence that the measurement is correct,Only 4.5%of the time will a value fall outside of that range due to chance;more likely it will be due to error,Calculation of Coefficient of Variation,The coefficient of variation(CV)is the standard deviation(SD)expressed as a percentage of the mean,Ideally should be less than 5%,Monitoring QC Data,Monitoring QC Data,Use Levey-Jennings chart,Plot control values each run,make decision regarding acceptability of run,Monitor over time to evaluate the precision and accuracy of repeated measurements,Review charts at defined intervals,take necessary action,and document,Levey-Jennings Chart,A graphical method for displaying control results and evaluating whether a procedure is in-control or out-of-control,Control values are plotted versus time,Lines are drawn from point to point to accent any trends,shifts,or random excursions,Levey-Jennings Chart,Levey-Jennings Chart-,Record Time on X-Axis and the Control Values on Y-Axis,Time(e.g.day,date,run number),Levey-Jennings Chart-,Plot Control Values for Each Run,Time(e.g.day,date,run number),Levey-Jennings Chart,Calculate the Mean and Standard Deviation;Record the Mean and+/-1,2 and 3 SD Control Limits,Mean,Day,+,1SD,+2SD,+3SD,-1SD,-2SD,-3SD,Levey-Jennings Chart-,Record and Evaluate the Control Values,Mean,Day,+1SD,+2SD,+3SD,-1SD,-2SD,-3SD,Findings Over Time,Ideally should have control values clustered about the mean(+/-2 SD)with little variation in the upward or downward direction,Imprecision=large amount of scatter about the mean.Usually caused by errors in technique,Inaccuracy=may see as a trend or a shift,usually caused by change in the testing process,Random error=no pattern.Usually poor technique,malfunctioning equipment,Statistical Quality Control Exercise,Hypothetical control values(2 levels of control),Calculation of mean,Calculation of standard deviation,Creation of a Levey-Jennings chart,When does the Control Value Indicate a Problem?,Consider using Westgard Control Rules,Uses premise that 95.5%of control values should fall within 2SD,Commonly applied when two levels of control are used,Use in a sequential fashion,Westgard Rules,“Multirule Quality Control”,Uses a combination of decision criteria or control rules,Allows determination of whether an analytical run is“in-control”or“out-of-control”,Westgard Rules(,Generally used where 2 levels of control material are analyzed per run),1,2S,rule,1,3S,rule,2,2S,rule,R,4S,rule,4,1S,rule,10,X,rule,Westgard 1,2S,Rule,“warning rule”,One of two control results falls outside 2SD,Alerts tech to possible problems,Not cause for rejecting a run,Must then evaluate the 1,3S,rule,1,2S,Rule,=A warning to trigger careful inspection of the control data,Mean,Day,+1SD,+2SD,+3SD,-1SD,-2SD,-3SD,1,2S,rule violation,Westgard 1,3S,Rule,If either of the two control results falls outside of 3SD,rule is violated,Run must be rejected,If 1,3S,not violated,check 2,2S,1,3S,Rule,=Reject the run when a single control measurement exceeds the+3SD or-3SD control limit,Mean,Day,+1SD,+2SD,+3SD,-1SD,-2SD,-3SD,1,3S,rule violation,Westgard 2,2S,Rule,2 consecutive control values for the same level fall outside of 2SD in the same direction,or,Both controls in the same run exceed 2SD,Patient results cannot be reported,Requires corrective action,2,2S,Rule,=Reject the run when 2 consecutive control measurements exceed the same+2SD or-2SD control limit,Mean,Day,+1SD,+2SD,+3SD,-1SD,-2SD,-3SD,2,2S,rule violation,Westgard R,4S,Rule,One control exceeds the mean by 2SD,and the other control exceeds the mean by+2S