Module 1: Topic 2: Quality Management

why is internal QC in lab procedures needed?

to minimise errors and ensure test result accuracy

what does internal QC involve:

• rigorous, systematic checks on instrumentation, methodologies and processes used in daily operations

• lab equipment is calibrated and functions optimally

What does Quality Control ensure:

ensures an analytical run produces results that are consistent with results from previous internal runs

while remaining an important part of labs quality activities, QC does not ________

guarantee the correct result

What type of errors are usually encountered?

• Data input errors - standards, calibration values

• Instrument errors - accuracy, precision

• Observer errors - reading errors, errors in equipment selection, analysis and interpretation

• Environmental errors - external factors affecting measurement

How is the uncertainty in measurement defined?

Repeatability, reproducibility, within-lab responsibility, between-lab reproducibility, stability, bias, drift, resolution, standard uncertainty

How is the uncertainty in measurement defined? Repeatability

variation among measurements made on the same object using the same conditions (precision)

How is the uncertainty in measurement defined? Reproducibility:

variation among measurements made on the same sample using diff conditions (instrument, operator, lab)

How is the uncertainty in measurement defined? Within-lab reproducibility:

precision within a single lab over time

How is the uncertainty in measurement defined? Between-lab reproducibility:

precision between diff labs

How is the uncertainty in measurement defined? Stability:

Variation among measurements made on the same object using the same conditions at diff times

How is the uncertainty in measurement defined? Bias:

diff between measurement average for the same object and its true value

How is the uncertainty in measurement defined? Drift:

continuous or incremental change over time

How is the uncertainty in measurement defined? Resolution:

smallest change in a quantity that causes a detectable change in output/indication

How is the uncertainty in measurement defined? Standard uncertainty:

uncertainty expressed as a standard deviation

What are some sources of uncertainty?

1. weighing uncertainties

2. volume uncertainties of pipettes

3. fluctuations of density

4. temp effects

5. metrological traceability

6. homogeneity of the sampling material

7. matrix of the sampling material

8. complex steps in preparation of the sample

9. stability of measuring signal

10. calibration of measuring device

what type of specimen is suitable for quality controls?

Specimen that has been assayed many times

• shelf life/open-vial stability

• liquid vs lyophilised

• medically relevant levels

• challenge range of instrumentation

• within-run/vial-to-vial variability

• matrix preservatives

What are some properties of QC materials?

• sample specially prepared for use as QC

• QC can be plasma or serum

• can be used to check for accuracy if value has been reliably determined (e.g. reference centre)

• should be controls of high, N and low values

• at least 1 QC specimen must be used for every batch analysis

• large number of specimens: use 1 control for every 20 specimens

• same material is used for external QC or as a calibrator

Why should we perform duplicate tests on specimens?

• provides way to check precision of routine work

Duplicate testing on specimens detects _____ random errors, but is it not sensitive to _________, nor will it detect ____________

1. random errors

2. gradual drift

3. incorrect calibration

what limitations are there of internal QC?

only detects change in performance between current and “stable” operation

• if original determination of mean contained systematic errors, they are not detected

• evaluation of original method needs to establish accuracy (as well as recovery and interference

  Ongoing comparison studies using external QA are needed to ensure systematic errors do not slowly increase and are undetected

What is External Quality Assurance (EQA) and who performs it?

• external comparison of the labs performance against other labs involved in similar activities

• evaluation by an outside agency of the performance by a no of labs on material which is supplied specially for the purpose

How is EQA organised?

usually organised on a national or regional basis

The analysis of performance is _______

retrospective

what is the objective of EQA?

objective is to achieve comparability, not necessarily accuracy unless the specimens have been assayed by a reference lab, using methods of known precision, alongside a reference preparation of known value

What are the functions of EQA schemes?

• Primary - Measurement

  • QA material, data collection and analysis

• Secondary - Assessment

  • analytical standards: allowable limits

• Tertiary - Corrective action

  • protocols for dealing with poor performance

  • evaluation and education

What are the outcomes of EQA schemes?

• compare lab results w peer group for:

  • accuracy

  • precision

  • linearity

• compare methods and instruments

What is EQA: Profiency surveillance?

critical supervision of all aspects of lab tests

• preanalytical: collection, labelling, delivery, storage of specimens before tests

• postanalytical: reading and reporting of results

includes maintenance and control of equipment and apparatus

What is EQA: Verification and standardisation

• EQA involves validating lab results against those of other accredited labs

• measurements are verified and standardised by sending samples to external entities such as RCPA-QAP

• EQA ensures alignment with industry standards and enhances reliability of findings

Differences of External QA vs Internal QC?

• ensures results from diff labs are comparable using same test, methodology and/or instrument

• an external proficiency organisation provides samples, and lab results are evaluated and compared to peers

• provides independent external evaluation of labs performance

• an investment in reducing risk of reporting incorrect results and minimising potential harm to patients and labs

• aids regulatory compliance; labs that participate in EQA may be preferred by their referring clinicians

• checks on internal QC and competency of lab staff

What are the three major activities of QAP?

1. Preventative

2. Assessment

3. Correction

What are some Preventative activites of QAP

activities performed before examining specimen that establish systems to promote accuracy in analytical testing

1. preventative equipment maintenance

2. instrument calibration

3. testing of media

4. induction and training of personnel

What are some Assessment activites of QAP

activities performed during testing to determine whether test systems are performing correctly

1. assaying standards and controls

2. maintaining control charts

What are some Correction activites of QAP

activities performed to correct system after an error has been detected

1. equipment troubleshooting

2. recalibration of instruments

What agencies address quality?

1. Royal College of Pathologists of Australasia (RCPA)

2. National Pathology Accreditation Advisory Council (NPAAC)

3. National Association of Testing Authorities (NATA)

What are Levey-Jennings control charts and what are they used for?

type of control chart used in lab studies to monitor and assess stability and correctness of lab processes over time

what are the Westgard analysis of quality

• 1_2s (warning)

• 1_3s (random error)

• 2_2s (systematic error)

• R_4S (random error)

• 4_1s (bias)

• 10_x (bias)