L1-QUALITY ASSURANCE Flashcards by Unknown Unknown

Ensures that the final results reported by the lab are correct.

QUALITY ASSURANCE

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-Ensuring accuracy and precision in the lab

QUALITY CONTROL

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TYPES OF QC
- AKA Internal Quality Control
- analyses of control samples together with patient specimens

INTRALAB

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TYPES OF QC
- AKA External Quality COntrol
- Involves proficiency testing programs

INTERLAB

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OBJECTIVES OF QUALITY CONTROL:

T - to check the stability of the machine
T - to check the quality of the reagent
T - to check the technical error

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TYPES OF QC
- sends out specimen to labs to test, results are sent back and results are compared

INTERLAB

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Characteristics of an Ideal QC Material:

With known analyte concentrations
Inexpensive and stable for long periods
No communicable diseases
No matrix effect

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TYPES OF REAGENT
- without any analyte added

REAGENT BLANK

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QUALITY CONTROL PARAMETERS
- Refers how well the test measures what it is supposed to measure.
- accuracy of the test
- how close the result to its true value

VALIDITY

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TYPES OF REAGENT
- Most specific analytical solution
- value will tell the CONCENTRATION OF THE UNKNOWN
- ONLY 1 ANALYTE

STANDARD REAGENT

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QUALITY CONTROL PARAMTERS
- Refers to how well the test performs in use over time.

RELIABILITY

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TYPES OF REAGENT
- Value will DETERMINE ACCURACY and PRECISION
- MANY ANALYTE

CONTROL REAGENT

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Done on apparently healthy indiv
not a basis for treatment

SCREENING TEST

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Indicating a person does not have the disease when, in fact, he/she does not

TRUE NEG

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Done on sick indiv
basis for treatment

DIAGNOSTIC TEST

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Indicating a person has the
disease when, in fact, he or she
does not

FALSE POSITIVE

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Indicating a person has the
disease when, in fact, he or she
does

TRUE POSITIVE

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Indicating a person does not have the disease when, in fact, he or she does

FALSE NEG

Ability of test to detect the smallest amount of analyte

SENSITIVITY

Ability of test to identify correctly those who have the disease (a) from all individuals with
the disease (a+c)

DIAGNOSTIC SENSITIVITY

➔ Ability of test to detect substances without interferences

SPECIFICITY

Highest value - lowest value

RANGE

Ability of the test to identify correctly those who do not have the disease (d) from all individuals free from the disease (b+d)

DIAGNOSTIC SPECIFICITY

TYPES OF ERROR
- constant when measurements are made under the same conditions
Causes: deterioration of reagents, improperly made standard solutions, contaminated solutions, calibration problems, failing instrumentation

SYSTEMATIC ERRORS

Measures of dispersion

STANDARD DEVIATION AND VARIANCE

Index of precision

COEFFICIENT OF VARIATION

SYSTEMATIC ERRORS CAUSES:

deterioration of reagents, improperly made standard solutions, contaminated solutions, calibration problems, failing instrumentation

TYPES OF ERRORS ➔ Unpredictable errors; often due to instrument, operator, and environmental conditions ➔ Causes: pipetting error, mislabeling of samples, temperature fluctuation, improper mixing of sample and reagent

RANDOM ERRORS

- The most commonly used histogram in QC

JENNY-JENNINGS CHART

- Results from QC fall within the confidence limit

IN CONTROL

- The values of the control fall outside the confidence limit

OUT OF CONTRL

Formed by the control that continues to either increase or decrease for a period of 6 or more consecutive days

TREND

Formed by the control that distributes themselves on one side (above or below) of the mean, with no tendency toward either a consistent fall or rise

SHIFT

- Developed by Dr. James O. Westgard ➔ Based on statistical concepts which is a combination of decision criteria or rules to assess if a system is in control

WESTGARD MULTIRULE SYSTEM

➔ How close the measured value is to the true value due to systematic error, which can be either constant or proportional

ACCURACY

-AKA LINEAR/DYNAMIC RANGE - Range of analyte concentrations that can be directly measured without dilution, concentration, or other pretreatment

Analytic Measurement Range

- Ability of a method to detect small quantities or small changes in concentrations of an analyte

ANALYTIC SENSITIVITY

➔ AKA Cross-reactivity ➔ Ability of a method to detect only the analyte it is designed to determine

ANALYTIC SPECIFICITY

➔ Range of analyte that a method can quantitatively report, allowing for dilution, concentration, or other pretreatment used to Extend AMR

CLINICALLY REPORTABLE RANGE

➔ Type of systematic error in the sample direction and magnitude; the magnitude of change is constant and not dependent on the amount of analyte

CONSTANT ERROR

- Effect of a compound/s on the accuracy of the detection of a particular analyte

INTERFERENCE

➔ Substances that cause interference

INTERFERENTS

➔ Lowest amount of analyte accurately detected by a method

LIMIT OF DETECTION

➔ Lowest amount of analyte that can be reported while achieving a precision target (e.g. lowest concentration at which a CV of 10% may be achieved)

LIMIT OF QUANTIFICATION