RAJESH NAIR DIRECTOR CALF-NDDB, ANAND, GUJARAT

Transcription

1 RAJESH NAIR DIRECTOR CALF-NDDB, ANAND, GUJARAT 1

2 Coverage Need of AQC in food testing laboratories Analytical quality system of food testing laboratories Relationship between Quality System, Quality Assurance & Quality Control Variables of data accuracy Analytical Quality Control (AQC)in food testing laboratories ISO/IEC 17025:2005: Concepts Internal quality control checks External quality control checks Trend Analysis using control charts Conclusion 2

3 Need of AQC in food testing laboratories Emerging food safety issues such as presence of microbial pathogens, bacteria, viruses, environmental toxins, allergens, adulterants, residues of agricultural drugs and toxic chemicals in food commodities, increased consumer awareness and rapidly growing international trade in food have stimulated the demand for accurate food safety testing all over the world. Information about the quality of the food commodity can be generated through quality testing in analytical laboratories. Analytical quality control, commonly shortened to AQC refers to all those processes and procedures designed to ensure that the results of laboratory analysis are consistent, comparable, accurate and within specified limits of precision. 3

4 Analytical quality system of food testing laboratories Quality is hard to define in a way that is appropriate for all situations Therefore, quality means that the laboratory results meet the customer s expectations and are accurate and defensible Analytical quality system of a food testing laboratory includes Quality assurance which further includes quality control. The meaning of the terms Quality Control and Quality Assurance(QA) often vary according to the context In practical terms, QA relates to the overall measures taken by the laboratory to regulate quality Whereas quality control describes the individual measures which relate to the quality of individual samples or batches of samples. 4

5 Relationship between Quality System, Quality Assurance & Quality Control Quality System Quality Assurance Quality Control Quality management works on the organizational level to implement an overall quality policy. A quality system refers to the organizational resources, processes and procedures to implement quality management, which is broader than both Quality Assurance (QA) and Quality Control(QC). QA program is the backbone of the laboratory quality system. QA provides a management tool within the organization. QC is a process within the QA program. The process is to collect evidence that the desired level of quality is achieved. 5

6 Variables of data accuracy Analytical variables Post analytical variables Preanalytical variables 6

7 Analytical Quality Variables PREANALYTICAL Laboratory facilities Laboratory facilities Design of the laboratory Environmental control Housekeeping control Staffing and organization Management structure Job description Staff training Staff performance Support personnel Analytical Standard material & Equipment Shelf life and storage Classes of equipment Maintainenance, calibration and repair Sample collection and handling Sampling Transportation Test material identification Control and storage Methods of analysis Selection method Validation of analytical methods Quality control procedures Quality assurance procedures Chemicals, reagent and standards POST ANALYTICAL External proficiency testing Maintenance of laboratory records Statistical Quality Control 7

8 Laboratory facilities Analytical Quality Variables Facilities must allow Laboratories work to proceed both effectively and safely Facilities should reflect the general features of work programme in long term rather than the specific pattern of current work Design of the laboratories Laboratory should be designed with efficiency in mind Even though the final design of the laboratory is made by architects and engineers the technical hand should be involved in establishing food control laboratories Design of the laboratory should meet minimum requirements to perform several functions such as chemical analysis of foods for proximate, trace metals, additive, nutrients residues and contaminants and for some basic food microbiology as well Environmental control Adequate control of temperature, humidity, and dust is important for staff comfort, instrumental performance and safe working(e.g. with flammable solvents) Computers need to be protected from strong magnetic fields Direct exposure of chemicals and reagents to sunlight and fluorescent light must be avoided Delicate balances and optical instruments may need to be protected from vibrations All these needs have to be documented and identified 8

9 Sampling Analytical Quality Variables Analytical data reported must reflect the composition of received samples as a whole Test material identification Without clear and unambiguous receipt and identification of each individual sample, quality assurance can not be maintained Each test material must be given an identification code, which can uniquely identify that material and records of its analysis Control and storage Deterioration of the test material invalidates the test results Therefore test material must be stored, so as to ensure their integrity, safety, legality and stability Equipment Each item of equipment used in the course of work must be known to be in the proper working order An instrument may be used only by staff with appropriate training For each instrument, the nature and frequency of performance checks and the person responsible for should be specified 9

10 SELECTION OF THE METHOD Analytical Quality Variables Any analytical method used on test materials must be followed in accordance with intended purpose of analysis and must have quality control procedure associated with it Reference methods Official methods In- house methods Screening methods Protocols VALIDATION OF THE METHOD Validation is a process of establishing documentary evidence demonstrating that a procedure, process, or activity carried out in production or testing maintains the desired level of compliance at all stages. 10

11 Analytical Quality Variables Initial Validations Methods must first undergo in-house validation and quality assurance programme which specify what parameters to include in validation Validation of a method developed in house must additionally identify factors which are revealed by an inter laboratory trial Thus it will include demonstration of the robustness of the method and identification of anyaspectofthemethodwhicharecriticaltoitsabilitytogenerateaccuratedata On going validation Some form of ongoing check that the method is continuing to work properly is necessary The nature and frequency of these checks need to reflect the complexity of the method, the degree of skills required, its reliability, track record, number of samples analysed and the quality of data required Usually the checks will take the form of some or all quality control procedures 11

12 Analytical Quality Control (AQC) in food testing laboratories Quality Control refers to a measuring process, or to check a result and provide assurance that all activities are performing within predetermined limits. Why QC? Safety of the consumer is being ensured through quality testing of food commodity in analytical laboratories. What is the goal? To check that the results being produced are fit for purpose. Rapid detection of SIGNIFICANT errors Provide accurate results in a timely manner Cost effective and simple to use To identify the source of error 12

13 ISO/IEC 17025:2005: General requirements for the competence of testing and calibration laboratories 4. Management Requirements 1. Organization 2. Management System 3. Document Control 4. Review of requests, tenders and contracts 5. Subcontracting of tests and calibrations 6. Purchasing services and supplies 7. Service to the customer 8. Complaints 9. Control of nonconforming testing and/or calibration work 10. Improvement 11. Corrective action 12. Preventive action 13. Control of records 14. Internal audits 15. Management reviews 5. Technical Requirements 1. General 2. Personnel 3. Accommodation & environmental conditions 4. Test & calibration methods & method validation 5. Equipment 6. Measurement Traceability 7. Sampling 8. Handling of test & calibration items 9. Assuring the quality of test & calibration results(5.9.1) 10. Reporting the results 13

14 ISO Clause says... The laboratory shall have quality control procedures for monitoring the validity of tests and calibrations undertaken. The resulting data shall be recorded in such a way that trends are detectable and, where practicable, statistical techniques shall be applied to the reviewing of the results. This monitoring shall be planned and reviewed and may include, but not be limited to, the following a. UseofCRMsand/orRMs; b. Proficiency-testing; c. Replicate tests; d. Retesting; e. Correlation of results for different characteristics 14

15 Quality control checks in daily life 15

16 Classification of AQC Internal Quality Control External Quality Control 16

17 Internal quality control checks Internal quality control consists of all the procedures undertaken by a laboratory for the continuous evaluation of its work in order to ensure the consistency of day-to-day results and their conformity with defined criteria Thismaytakeavarietyofformsincludingtheuseof 1. Replicate determinations 2. Reagent blank 3. Method blank 4. Solvent blank 5. Positive control 6. Negative control 7. Use of in-house standards 8. Use of internal standards 9. Use of certified reference material 10. Spike recovery 11. Retesting/Blind sample 12. Calibration verification 13. Trend analysis using control charts 17

18 Replicate determinations Conducting repeat analysis of the same sample Where results are customarily reported on the basis of single determination, it should be practice to include in an analytical batch replicate determinations on the same test material Preferably Replicate of the same test material should be randomised in batch and ideally the analyst should not be aware of their presence 18

19 Blank/Reagent Blank/ Method Blank/ Solvent Blank Ablankormethodblankdetermination isananalysisofasamplewithoutthe analyteor attribute, or an analysis without a sample, i.e. going through all steps of the procedure with the reagents only It is used to determine the contribution of the reagents and the preparative analytical steps to error in the measurement For convenience, some analysts practice "forcing the blank to zero" by adjusting the instrument. Some instruments even invite or compel analysts to do so This is equivalent to subtracting the blank value from the values of the standards before plotting the calibration graph From the standpoint of Quality Control this practice must be discouraged This is becoming more and more common practice with modem sophisticated hi-tech instruments Whateverthecase,adecisiononhowtodealwithblanksmustmadeforeachprocedure andlaiddowninthesopconcerned 19

20 Positive control Where it is anticipated that the majority of the test portion will not contain significant amounts of analyte, it is important to analyse test portion to which analyte has been added and show that the analysis produces expected results This approach can be used to check the effectiveness of the screening test or in presence or absence analysis It is useful for checking the ability to correctly identify test portions containing analyte at the action level Itcanbeusedtoassestheincidencesoffalsenegatives This practice can be proved to be more useful in nutritional analysis of a product claimed to be fortified with the respective nutrients 20

21 Negative control In a reverse situation of positive control where, most test portion contains significant amount of analyte, it is important to include number of test portions which are essentially free of the analyte so as to provide confidence that laboratory contamination levels are acceptably low Use of a matrix which is essentially free of the analyte is particularly important in analysis for trace amounts of additives In case of residues and contaminants it is preferred to have reagent blanks, which contain no test matrix The other form of negative control uses test materials known to contain analyte at levels just below the action level, results from these provide a check on the incidence of false positive 21

22 In-house standards When a large number of similar analysis are to be conducted over a period of time it is usefultochecktheselfconsistencyofthedatabyuseofaninhousestandardmaterial For this a relatively large amount of the matrix containing an appropriate level, it can be homogenised and kept under conditions where the analyte is stable At specified intervals test portions from this in-house standards are included in a normal analytical batch Over a period of time it is possible to see whether the method is giving consistent data andtoobtainanestimateofthelongtermprecision A large number of repeat analysis conducted on the in-house standard over a short time allow the in-house precision(repeatability) of the method to be calculated 22

23 Internal standards Internal standards are similar in analytical behaviour to the compounds of interest, and notexpectedtobefoundinthesamples The response of the target compound is normalized to the response of the reference standard. This reference standard is called an internal standard because it is contained within the aliquot of the sample or sample extract that is actually injected into the instrumentation The ratio of the peak area (or height) of the target compound in the sample or sample extract to the peak area (or height) of the internal standard in the sample or sample extract is compared to a similar ratio derived for each calibration standard The analyst needs to demonstrate that the measurement of the internal standard is not affected by target analytes, surrogates or by matrix interferences This is not as useful for GC and HPLC methods with non-ms detectors, unless the internal standards could be separated from target compounds chromatographically The retention times of the target compound and the internal standard may be used to calculate the relative retention time (RRT) of the target compound and can then be used to compensate for small retention time shifts 23

24 Use of Certified Reference Material These are homogenous test materials in which the analyte has been determined with great care usually by a number of expert laboratories and preferably using a number of different analytical techniques By analysing appropriate certified reference material from time to time it is possible to check the accuracy of the results The in-house standards demonstrates the precision (consistency) of the data being produced while CRM demonstrates the accuracy i.e. how near the results are to correct values Since most analytical instrumentation is comparative, it requires a sample of known composition (reference material) for accurate calibration. These reference materials are produced under stringent manufacturing procedures and differ from laboratory reagents in their certification and the traceability of the data provided. Quality management system involving laboratory accreditation as per ISO/IEC requires metrological traceability to Certified Reference Materials (where possible) when using reference materials for calibration 24

25 Spike Recovery Spike, recovery is an important method for assessing the accuracy of analytical techniques for particular sample types Matrix match standards are ideal for residue testing to get a better recovery Spike-and-recovery is used to determine whether analyte detection is affected by a difference between the diluent, dilution accuracy of calibration standards prepared, the standard curve and the sample matrix Recovery shall be determined in each batch of samples and the recovery factor obtained for the specific batch shall be used in quantitative determination of an analyte in sample Standard recovery criteria are as given in the table, again it depends on respective regulations. concentration Accepted recovery range Less than 1 µg/kg -50 to +20 Between 1 to 10 µg/kg -30 to +10 More than 10 µg/kg -20 to +10 Calibration curve should include at least five calibration points and the working range should be clearly described 25

26 Retesting /Blind sample Retesting of retained sample The stable parameters to be considered as the storage may adversely affect the result The variation should be recorded and investigated OneofthecommonlyfollowedQCinfoodlabs. 26

27 Calibration verification Calibration is the process of testing and adjusting an instrument, kit, or test system readout to establish a correlation between the instrument s measurement of the substance being tested and the actual concentration of the substance Use of CCV standards are recommended in heavy metal testing Calibration verification is the periodic confirmation by analysis of a calibration standard that the instrument performance has not changed significantly from the initial calibration Calibration verification should also be performed under the following conditions 1. Whenever major maintenance is performed or a critical component part of an analyser has been replaced 2. Whenever reagent lots are completely changed (unless it has been stated and shown that these lot changes do not affect test results, as with manufacturer s instructions and guidelines in package inserts and analyser specific manuals) 3. When control values are found to be continually unacceptable, as with shifts and trends in Shewharts/Levy-Jennings graphs over a period of time 27

28 AQC checks in Food Microbiology Lab Standards & critical consumable checks Reference culture quality checks Critical consumable quality verification Media/Diluent sterility checks Spiking samples with reference microbial cultures Duplicate analysis of sample for enumeration tests Analysis of same sample by different method, personnel, equipment etc. 28

29 External quality control Laboratories may wish for, or indeed may be required to have, an external check on their performance. For this, they need to participate in Proficiency testing(pt) schemes. Example of EQC includes 1. Inter laboratory comparisons 2. Proficiency Testing Inter laboratory comparison It is inter comparison of measurement results of a laboratory Successful participation in an inter laboratory comparison is one of the necessary requirements of quality control of data generated from food testing laboratories when PT is not available. 29

30 External quality control Proficiency testing External proficiency testing is an independent external assessment of the correctness of the results and provides an impartial test of analytical quality: which can be done through an inter laboratory proficiency testing Usually it involves presenting the analyst with the test material and requesting specific information about its properties such as moisture, fat, protein, ash, fatty acid composition, toxic metal concentration, pesticide/drug residues etc. Ideallytheanalystshouldnotbeawarethattheitisproficiencytest,butoftenthiswillnot be feasible Asinglebadresultfrombadtestingmaypromptactionstorectifythematter,butasingle good result in no way guarantees that all results are of quality achieved on the proficiency testing The proficiency test therefore needs to be conducted on quite regular basis 30

31 Trend Analysis using control charts The control chart, also known as the process-behaviour chart is one of the seven basic tools of Statistical Quality Control A control chart is a graph of test results with respect to time or sequence of measurements, with limits drawn within which results are expected to lie when the analysis is in a state of statistical control. A procedure is in statistical control when results consistently fall within established control limits. It reveals trends that in themselves do not yet result in a rejection of analytical results, but it will give early warnings of issues or problems that are developing. The accuracy of an analysis or manufacturing process is monitored using one or more of the following control charts: Shewhart control chart Moving average control chart CUSUM control chart 31

32 Shewhart Control Charts Valueofthecontrolsample/QCstandardforeachbatchisplottedontheyaxis. The batch number(or measurement number) is plotted on the x axis. If the analysis (or process) is working satisfactorily the points should be randomly distributed about the target value and between the upper warning limit (UWL) and lower warning limit (LWL). Warning limits at the target value±2s (where s is the standard deviation of a large number of replicate analyses) and the action limits at the target value ±3s 32

33 Moving average Control Chart The average results of a given number of batches is plotted, instead of plotting the result for each individual batch. Each point plotted will be the average of that batch, plus a given number of batches immediately before it. Advantage: This smoothens the data making trends easier to see. Disadvantage: This delays the appearance of changes affecting the analysis. The warning limits are the target value±(2s/ n) and the action limits are the target value ±(3s/ n), where n is the number of batches used to calculate the moving average. 33

34 CUSUM Control Chart This chart shows up trends more quickly than a Shewhart chart. In this chart, the difference between each QC value and the target value (QC result target value) is calculated, taking note of the sign. The differences are added and plotted against batch number. If the analysis is working satisfactorily the points will wander about 0(the x axis). If there is a problem with the analysis or process, the points will move away from the x axis,upordown. Target value 34

35 Trend-Out of Control The warning limits can be expected to be breached once in 20 occasions, therefore no action may be required for a single breach when all other points lie within the warning limits and are randomly distributed around the target mean. More fall outside 3s (outside the upper or lower control limits) Two or more consecutive values fall outside 2s (outside the upper or lower warning limits) on the same side of the mean A series of seven or eight consecutive values fall all above or all below the mean An increasing or decreasing trend is detected. 35

36 Conclusion Laboratory accreditation does not guarantee that the laboratory is of high quality, but it helps give customers confidence that the lab is capable of producing quality data. Implementation of the AQC requires resources and investment, so there is a significant cost to quality. By applying systematic and continuous QC tools in routine testing, a lab can achieve the accuracy in their reported results. The new trend includes software programs to implement QC activities and statistical analysis. The responsibility of QC does not lie with only the laboratory management or QC /QA department personnel. Each individual working in the lab is responsible for the implementation of QC techniques. QC is a collective responsibility. 36

37 Thank You For Your Kind Attention