Quality assurance and quality control

Quality assesment

Includes all action a laboratory takes to measure and monitor performance of the laboratory processes

Quality assurance

Refers to all the process a laboratory takes to ensure quality in test results

Quality control

Provides the tools to detect problems early and prevent error from exceeding established quality requirements

Quality improvement

Process thag determine the cause of the problem and provide input to eliminate the problem

External QC

Process by which laboratory uses an outside unbiased source to verify the quality of patient results

Calibrator/Standard

Is a solution that contain a known amount of an analyte and is used to calibrate an assay method

Controls

Are patient-like substances run alongside with patient samples

Mean

Defined as the average of all the data points or values

Median

Defined as the middle data observed once the data is arranged

Mode

Value that occurs with the greatest frequency

Range

Defined as the difference between the highest and lowest value in a data set

Variance

Defined as the measurement of the average squared distance of data points from the mean

Degrees of freedom

Defined as the number of independent data points from the mean

Standard deviation

Defined as the square root of the formula for variance. It is the measurement statistic that described the average distance each data point in a normal distribution is from the mean

Confidence interval

Defined as the limits between we expect a specified portion of a population lie

Coefficient of variation (CV)

Is the standard deviation expressed as a percentage of mean

Trend

Is the a gradual change in the mean that proceeds one direction

Accuracy

Is the ability to obtain the established or true value for a sample

Precision

Is the ability to obtain the same value for repeat measurement of a sample

Shift

Is an abrupt change in the mean that becomed continous

Random error

Is the error occurs without ang real pattern

Systematic error

Is the error that is continous and affects all results equally

Sensitivity

Is the ability of an analytical method to measure the smallest concentration of the analyte interest

Specificity

Is the ability of an analytical method to measure only the analyte of interest.

Intralab (internal QC)

Analysis of sample together with the patient samples

Intralab (Internal QC)

Detects changes in performance between present operation and stable operation

-important for daily montioring

DOH

Mandates the proficiency testing program

-coensides the standard standings

Interlab (external QC)

Involves proficiency testing programs

-important in maintaining long term accuracy of the analytical methods

-difference of more than 2 results woould indicate that the laboratory is not in agreent with other laboratories

Stability of machine

Quality of reagent

Technical errors

Objectives Of QC (to check)

Pipetting

Most technical error

Characteristics of an Ideal QC material

1. Resemble human sample

2. Inexpensive and stable

3. No communicable disease

4. With known analyte concentration

5. Convenient packaging

Bovine

Most quality common material

Quality assesment (verification)

1.sample collection

2. Sample processing

3. Reporting of results

4. Interpretation of the final result by the physician

Pre-analytical CQI

Analytical CQI

Post-analytical CQA

Components of an effective continous quality improvement

Pre-analytical CQI

1.correcting ordering of tests

2.preparation of the patient

3.correct identification of the patient

4.timely transportatiom of the specimens

5.proper handling of the sample

(Outside the laboratory promises)

Analytical CQI

1.proper labelling and use of reagents

2.periodic calibration of pipetting devices

3.preventive maintenance

4.periodic checking of temperatures

5.periodic checking of accuracy

5.constant assurance that safety procedures are followed (inside the laboratory)

Post-analytical CQA

1.verification of calculation on final reports

2.review of test results

3.timeliness of reporting values to patient chart

4.verification of correct interpretation of lab test by physicians

5.delta check

Delta check

Comparison of current result to previous result

Examples of Quality improvement

1.monitoring of hemolyzed samples

2.processing of STAT sample

Control

Are used to montitor the performance of an assay method once it calibrated

Gaussian Curve

-Occurs when the data set can be accurately described by the SD and the mean

-occurs when the data elements are centered around the mean

-focuses on the distribution of errors

Cumulative Sum Graph

-earliest indication of systematic error

-the commonest method is the V-mask

-identofies consistent bias problems

-requires computer implementation

Youden Graph

-use to compare the results obtained on a high and low control serum from different laboratories

-the mean values for one specimen is plotted on the ordinate (y-axis) and the other specimen on the abscissa (x-axis)

Shewhart-Levey-Jennings chart

-most widely used chart

-allows laboratories to apply multiple ryles without the aid of a computer

-is a graphic representation of the acceptablr limits of variation

Outliers

Are control values that are far from the main set of values

Error detection

What error was made?

Where was it made?

When was it made?

Who made it?

Why was it made?

The probabilty of error dectection

The probability of false rejection

Control monitoring and error detection.

Probability of error detection

Describes the ability of the detector to detect an error that beyond the stable impresicion of the instrument

Probability of false rejection

Describes the probability of an alarm when no error exists

Quality planning for QC

Multi-rule system

Multi rule system

Uses multiple rules that define specific limits for control values

Example: westguard rules

1-ODD

Random error

2-EVEN

Systematic error

Random error

Is present in all measurements

-due to instrument,operator and environmental conditions.

Example: pipetting error, mislabelling, temperature flocculation, improper mixing of sample and reagent

Systematic Error

-error that influences observations consistently in one direction

-measure the agreement between the measured quantity and the true value

Examples: detorioration of reagents

Contamination leaky ISE's poorly written procedures

Clerical error

Highest frequency of clerical errors occurs with the use of handwritten labels and request forms

Proficiency testing

Is an important component of quality management program

Peer group evaluation

Allows a laboratory to verify that it is using a method according to the manufacturer's specifications and producing patient results that are consistent with those of other laboratories using the same method

Proficiency testing

Peer group evaluatio

Two laboratories agreement