BIOL 325 LECTURE 16 QUALITY CONTROL STUDY GUIDE

Exam 4

what are clinical laboratory improvement amendments?

to establish quality testing standards to ensure consistent patient results

what is the oxford dictionary definition of CLIA?

the maintenance of a desired level of quality in a service or product, especially by means of attention to every stage of the process of delivery or production

why aren’t QC regulations well defined for molecular diagnostics? what are they implemented with?

• molecular diagnostics is an explosive field due to more assays being released and new targets need to be analyzed

• Molecular diagnostics are implemented with increasing scope and speed in routine clinical labs

what is quality assurance? what is the WHO definition?

• QA = assuring the patient and the clinician that the result is correct and that you have done it on the right specimen

• WHO definition = the total process whereby the quality of the laboratory reports can be guaranteed

what is QA summarized as?

• right result, at the

• right time, on the

• right specimen, from the

  • different specimens are needed for different tests

• right patient,

  • can cause false positives

• with the result interpretation based on,

  • correct reference data

• and at the right price

what is quality control controlling? what does it involve? what is the control sample processed along with?

• quality control is controlling every single step in the procedure ensuring you have precision and accuracy

  • an important part of a QA program

• involves the use of control samples to monitor the precision and accuracy of a test produce

• control sample is processed along with the patient samples and the results are compared

what is the difference between quality assurance and quality control?

• quality assurance ensures overall quality in processes, making sure you’re doing the right things the right way.

• quality control specifically monitors and verifies test results, making sure you get the right results.

• QA focuses on preventing errors, whereas QC detects them in the final product.

what are erroneous results?

at best a nuisance/annoying and at worse can cause considerable harm

how do you minimize error?

strict adherence to protocols at EVERY stage of the testing process

where are the three areas that errors can occur? describe them

1. pre-analytical which is outside of the lab

   • person drawing, labeling, transporting the specimen

2. analytical which is within the lab

   • technician is responsible here

3. post-analytical where the correct result is incorrectly recorded in the patients record

   • technician may or may not be responsible for this

how do you minimize pre-analytical error? what does quality assurance include?

• by following proper sample acquisition, labeling the sample correctly (barcoding), and following the holding and storage requirements

  • CLSI was developed for this which tells them what to do

• quality assurance includes monitoring and controlling

  • personnel competence = always monitored

  • quality of materials like reagents and instruments

  • reliable reporting of test results

what are the 6 measurements of test performance?

1. accuracy

2. precision

3. analytical sensitivity

4. analytic specificity = include interfering substances

5. reportable range of test results

6. reference intervals or normal values (if applicable)

what are the measurements of test performance for quantitative assays? what is LOD?

1. linerarity

2. dynamic range

3. limit of detection (LOD)

   • kind of associated with sensitivity

   • lowest LOD = how low can you go/how sensitive is it at the lowest LOD?

   • high LOD = how much can be detected before it cannot be told apart

4. lowest limit of quantification (LLOQ)

what is established for genetic tests?

• establish clinical usefulness and validity, including clinical sensitivity and specificity, and positive and negative predictive value

  • just because you made a great assay doesn’t mean it serves a purpose in a diagnostics lab

what is accuracy?

• are the results right or wrong?

  • essentially assessing if test results are correct or close to the true value

what is precision? what is it an indication of? what is it described by?

• the expression of variability in an assay

  • do you get a similar/consistent answer every time?

• indication of the amount of random error

• described by: standard deviation, variance, coefficient of variation

what is analytical sensitivity? how do reference samples measure test of performance?

• how sensitive is your assay?

• at what intervals do your reference work?

  • hope to have a lot of intervals so you can make a standard curve

what are control samples?

samples that are used to monitor the performance of an assay to make sure it is working as intended and to ensure the reliability and accuracy of the test results

when should control samples be taken?

taken in extraction phase when practical, amplification phase, and detection phase

when possible, what should be similar?

when possible, quality-control samples should be similar to patient specimens in order to monitor the quality of all analytical steps

what is extracted during the extraction phase? what is the control format required during this phase, why? what should be in the same tube, why?

• nucleic acids (DNA/RNA) are extracted from specimens either manually or via automated method

• control format required: whole cells, whole bacteria, or virus are best because they mimic the patient sample

• control should be in the same tube before extracting which tells you if the extraction worked

what is amplification? what is the control format required during this phase, why?

• production of multiple copies of a DNA sequence for quantification or strain typing in PCR

• control format required: positive controls could be purified nucleic acid, such as synthetic standard, or a whole genomic extract

  • ensures that the amplification process is working correctly and all of the reagents and instruments in the process are working

what is the detection phase? what is the control format required, why?

• detecting the intended target and positive control

• control format required: positive control should be purified nucleic acid, such as a synthetic standard, or a whole genomic extract

  • ensures that the detection system is working as intended and confirms fluorophore or chromatin is satisfactory

what is verification talking about? what are you given with it?

talking about the equipment and you’re given equipment controls to constantly run because they monitor the performance of the equipment and that it provides accurate results

what is generally conducted upon for verification? how many times are the tests conducted but what does it depend on?

• generally conducted upon installation of a system or new use of a method, requiring that testing be done a certain number of times to confirm the system or method is working properly

• labs often conduct the test 20 times successively and have to get the same results each time

  • the number of tests conducted depends on the lab’s processes and the regulation it follows

what are internal process controls built into?

internal process controls are built into instruments to ensure that the instruments are running properly

what are internal process controls doing in same tube with the pathogen target?

simultaneously extracted and amplified (or only amplified) in the same tube with the pathogen target

what should internal process controls always be combined with? what does it rule out?

• should always be combined with an external positive control to prove the functionality of the reaction mix for amplification of the pathogen target

• rules out inhibition, among other malfunctions, and confirms that a negative result is truly negative

what does homologous and heterologous mean when referring to internal controls? what about intrinsic and extrinsic?

• homologous = uses the same primer

  • heterologous = uses primers to a different target

• intrinsic = same isolated DNA/same patients DNA

  • extrinsic = different sequence from the target sequence

what are external controls? what is an example of them? what does it ensure?

• independent control that provides a true challenge to the system or process being testing to ensure this system or process is working properly

• ex. sending the sample sample to a different lab that runs a similar but subtly different technique

• ensures experiments are valid

what are the four reasons why quality control is done?

1. protects patients/reduces risk of misdiagnosis

2. ensures procedures, equipment and materials are working properly

3. ensures personnel competence

4. improves daily workflow and produces consistent, reliable results

what are the 8 QC best practices?

1. use quality control materials with known values (standard curves)

2. include quality control in the procedure manual

3. monitor equipment, media, reagents, stains, and antigens

4. train and monitor personnel

5. participate in inter-laboratory comparison program (checks methodology)

6. perform verification as needed

7. perform validation as needed

8. keep detailed records

what are systematic errors?

• errors within the test system or methodology and affects the accuracy of the results

  • mean of a data set differ from the accepted value

what are the three examples of systematic errors?

1. incorrect instrument calibration

2. unprecise or malfunctioning dilutors and pipettes

3. reagents that lost their activity

what are four ways that systematic errors are detected?

1. analyzing standard samples

2. using an independent analytical method

3. performing blank determinations

4. varying the sample size

what is the best way to eliminate bias regarding analyzing standard samples?

the best way to estimate the bias of an analytical method is by analyzing standard reference materials, materials that contain one or more analytes at well-known or certified concentration levels

why should independent methods differ?

should differ as much as possible from the one under study to minimize the possibility that some common factor in the sample has the same effect on both methods

how can errors be detected by varying the sample size?

as the size of a measurement increases, the effect of a constant error decreases which results in the constant errors being detected by varying the sample size