1 Quality Assurance and Quality Control in the Molecular LaboratoryChapter 16 Quality Assurance and Quality Control in the Molecular Laboratory
2 Objectives Describe proper specimen accession for molecular testing.Describe the optimal conditions for holding and storage of specimens and nucleic acid. Explain the basic components of molecular test performance, including quality assurance and controls. Discuss instrument maintenance, repair, and calibration. Describe recommendations for preparation and use of reagents in the molecular laboratory. Explain documentation and reporting of results.
3 Specimen Accession Pre-analytical error is the consequence of erroneous or misleading results caused by events that occur prior to sample analysis. The condition of the specimen and, if necessary, the chain of custody is reviewed upon receipt in the laboratory. No specimen is accepted without proper labeling and identification. If a specimen is unacceptable, the disposal or retention of the specimen is recorded.
4 Precautions All specimens are potentially infectious and should be handled with standard precautions using proper personal protective equipment (PPE). Gloves are highly recommended not only as part of standard precautions, but also to protect nucleic acids from nuclease degradation. Gloves are absolutely required for handling of RNA. Transmission-based precautions, including respirators, are used with airborne or contact transmissible agents. Contact precautions are designed for direct patient care.
5 Specimens for Molecular TestingSpecimens of minimal cellular content are often analyzed. Cross-contamination must be avoided. The specimen is inspected for hemolysis. If white blood cell lysis has occurred, DNA and RNA yield will be reduced. Solid tissues are best analyzed from fresh or frozen tissues. The quality of nucleic acid from fixed tissue depends on the fixing process and the fixative used.
6 Specimen Collection: AnticoagulantsAdditive Color Testing None Red Chemistry, serum, viral antibody studies Sodium heparin (freeze dried) Green Immunology, virology studies Sodium heparin Brown Cytogenetic studies, molecular studies Tripotassium EDTA (7.5-15% solution) Lavender Virology, molecular biology Acid citrate dextrose (ACD) solution Yellow Molecular biology
7 Specimen Holding and Storage: DNASpecimens Blood, Bone marrow, Fluids <1 day, 23°C; 3 days, 4°C WBC, >1 year, -20°C or -70°C Tissue 23°C (not recommended) <1 day, 4°C >2 weeks, -20°C >2 years, -70°C Isolated DNA <26 weeks, 2-25°C 1-3 years, 4°C (1 year for Southern blot) <7 years, -20°C, -70°C (not frost-free)
8 Specimen Holding and Storage: RNASpecimens Blood, Bone marrow, Fluids <2 hours, 23°C or 4°C 5 days, 23°C; 7 days 4°C in denaturant 1-2 weeks, -70°C in denaturant WBC, 2-4 weeks, -20°C; >6 months, -70°C Tissue <2 hours, 4°C snap frozen, -70°C, >2 years nitrogen vapor -140°C– -150°C, >2 years Isolated RNA 2–25°C (not recommended) <30 days, -20°C in DEPC-treated water <30 days, -70°C in DEPC-treated water >6 months, -70°C in ethanol
9 Laboratory Preparation for RNA AnalysisBench, equipment separate laboratory area designated RNase free or RNF wipe with RNase ZAP, RNase AWAY Disposables certified RNase free rinsed in 0.1% diethyl pyrocarbonate (DEPC) Reagents add 0.05–0.1% DEPC (except Tris) test with RNase Alert (Ambion) Reactions add Rnasin (Promega)
10 Test Performance Federal regulations from the Food and Drug Administration (FDA) require validation of the performance of clinical test methods and reagents in accurately detecting or measuring analytes prior to use in human testing.
11 Criteria for Assessment of Test PerformanceThe clinical sensitivity of an assay equals: TP TP+FN X 100 The clinical specificity of an assay equals: TN TN+FP X 100 TP = true positive, TN = true negative, FN = false negative, FP = false positive
12 Criteria for Assessment of Test PerformanceThe clinical accuracy of an assay equals: TN + TP TN+TP+FN+FP × 100 TP = true positive, TN = true negative, FN = false negative, FP = false positive
13 Test Validation Test validation is performed on specimens of types that will be encountered in the routine use of the test. The number of specimens tested varies with the procedure and availability of test material. Results from the new test methodology are compared to results from established procedures or correlated to clinical diagnosis.
14 Test Validation Commercially developed and FDA-approved molecular methods are verified by using the purchased reagent sets to test validation specimens in the laboratory. If the commercial test is modified, validation is required to show equal or superior performance of the modified procedure. Once a procedure has been established, the method is documented in the laboratory according to Clinical and Laboratory Standards Institute (CLSI) guidelines.
15 Proficiency Testing Proficiency testing refers to external specimens from a reference source supplied to independent laboratories. The College of American Pathologists (CAP) and other organizations supply specimens for molecular analysis. If proficiency specimens are not commercially available, laboratories can exchange blinded split specimens, or alternatively, blinded specimens measured or documented by independent means such as chart review can be tested within the laboratory.
16 Controls Controls are samples of known type or amount that are treated like and run with patient specimens. With qualitative tests, a positive, negative, and in some cases, a sensitivity control, are required. In quantitative methods, high-positive, low- positive, and negative controls are included. For amplification procedures, amplification controls are required to avoid false-negative results.
17 Controls Quantitative PCR methods that automatically analyze results require a standard curve or dilution series of the positive control. In methods requiring detection of a target-specific product or relative amounts of target, internal controls are run simultaneously, preferably in the same reaction mix as the test specimen. e.g., housekeeping genes, centromere probes, amplification controls
18 Quality Assurance Periodic review and documentation of test results is required. Molecular quantitative methods should have a defined dynamic range, sensitivity level, and accuracy. Assay levels that distinguish positive from negative results (cut-off values) must also be well defined and verified at regular intervals.
19 Instrument MaintenanceManufacturers supply recommendations for routine maintenance. The laboratory maintains a schedule and instructions for all routine maintenance. Technologists should be aware of the limits of user-recommended repairs and when service calls are indicated. Regular calibration, or fitting an instrument or test system output with the actual concentration of a reference analyte, is required for detection systems.
20 Reagents Instructions on the preparation of reagents and the quantities used in each assay are included in the written laboratory protocol. The sequences of primers and probes are also documented. Primer binding sites and sizes of expected amplicons are also documented.
21 Analyte Specific ReagentAnalyte-specific reagents (ASR) are probes, primers, antibodies, or other test components that detect a specific target. Most ASRs used in the molecular laboratory are class I, not subject to special controls by the Food and Drug Administration. Class II and III ASRs include those used by blood banks to screen for infectious diseases or those used in diagnosis of certain contagious diseases such as tuberculosis.
22 Hazardous Chemicals The National Fire Protection Association has developed a series of warning labels for universal use on all chemical containers. Flammability 0-4 Health hazard Instability Special hazards O, W
23 Hazardous Chemicals: Transport and StorageSecondary or reinforced containers are required for transport and handling of dangerous chemicals such as concentrated acids or phenol. Volatile and flammable reagents are stored in properly vented and explosion- proof cabinets or refrigeration units.
24 Hazardous Chemicals: Radioactive MaterialThe Nuclear Regulatory Commission (NRC) requires that laboratories working with radioactive reagents maintain a radiation safety manual providing procedures for the safe handling of radioactive substances. Use and storage of radioactive reagents are in designated areas.
25 Documentation of Test ResultsTest results in the form of electropherograms, gel images, or autoradiograms should be of sufficiently high quality that results are unequivocal. Documentation of assay conditions, reagent lot numbers and quality and quantity of the isolated DNA or RNA is required. In situ results such as FISH are correlated with histological findings (stained sections) of tissue morphology. Raw data is retained with the final report and clinical interpretation of the test results.
26 Reporting Test ResultsThe test report must convey the method or manufactured kit used, the locus, mutation or organism tested, the analytical interpretation of the raw data, and the clinical interpretation of the analytical result. The likelihood of false-positive or false-negative results are also included on a report.
27 Reporting Test Results: DisclaimerWhen Class I ASRs are used in an analytical method, the following disclaimer is included in the test report: "The FDA has determined that such clearance or approval is not necessary. This test is used for clinical purposes. It should not be regarded as investigational or for research. This laboratory is certified under the Clinical Laboratory Improvement Amendments of 1988 (CLIA-88) as qualified to perform high complexity clinical laboratory testing.“ (Molecular Pathology Checklist, College of American Pathologists, Northfield, IL)
28 Summary Proper specimen handling is required for accurate test results. Specimens should be held and stored under conditions that will preserve nucleic acids. Molecular test performance is monitored by the use of quality controls. Instruments should be maintained and calibrated for accurate detection and measurement of analytes. Reagents are prepared, stored, and used as recommended by manufacturers and/or laboratory protocol. Raw data should be documented and results clearly reported.