PRELIMS WEEK 5 Flashcards
- Ability of a method to detect and measure even the smallest
amount or concentration of a particular analyte of interest
SENSITIVITY
- Refers to analytical measurement or testing that is used to
asses the quality of an analytical data
QUALITY CONTROL
- It is a system of techniques to ensure with a specified degree
of confidence that the result obtained from each series of
analysis is true and correct.
QUALITY CONTROL
talks about “the system,” the sum of all of the activities in which the laboratory is engaged to ensure that the information generated is correct.
QUALITY ASSURANCE
_________ Sensitivity can measure minute concentration
Analytical
________ Sensitivity, tests must always yield a positive result in the presence of a disease.
Diagnostic
The probability that subjects or patients with a positive
screening test truly harbored the disease
POSITIVE PREDICTIVE VALUE
BEing able to give similar results. Associated with
reproducibility.
PRECISION
Solution without the specimen
* With reagent
* Set the reading to zero
* For accuracy
BLANK
It is composed of one known constituent only and used as
a basis of reference for the calculation of the value of the
unknown.
Checking accuracy
standard solution
A solution (either commercially or non-commercially
prepared) composed of several known constituents which
can be run simultaneously with the test to check the accuracy
of the results.
for precision
control solution
- Measure of central tendency
Arithmetic Value or Mean or average (x)
The value of observation that divides the observation into two
group, the midpoint of the distribution
mean
- Used to compare the means or standard deviations of two
groups of data
Inferential Statistics
Used to determine whether there is a statistically significant
difference between the means of two groups of data
t test
Used to determine whether there is a statistically significant
difference between the standard deviation of two groups of
data
f test
Are errors encountered in the collection, preparation and
measurement of samples
variations
Affects accuracy, you will have failures in hitting or obtaining
the target value
systematic error
Error by chance, factors that can affect the precision
random error
It will group any series of measurement in the same sample
in a cluster around the mean in a bell-shaped curve
gaussian curve / normal
distribution curve
- Obtained by plotting the values from multiple analysis of a
sample - It focuses of the distribution of errors
- Confidence interval 1 = 68%, 2 = 95%, 3 = 99%
gaussian curve
- Plotted with the accumulated differences from the mean of
individual values with the middle value being zero. - Calculates the difference between Quality Control results
- Give the earliest indication of systematic error, sensitive to
small and persistent error
cumulative sum graph
- A 2-mean chart drawn at right angles to one another with the
one set of values on one axis another set of values on the
other axis. - Used to compare results obtained of a high and low control
serum from different laboratories
youden plot
- Detects systematic errors
- Also referred to as Twin Plot or Two-Way average chart or
Two Mean Chart
youden plot
- Most commonly used chart for QC recording
- A graphic representation of the acceptable limits of variation
in the results of an analytical tests.
Shewhart-Levey Jennings Chart
- Allows us to apply rules that help identify if a test is
acceptable or not - Can be used even without the use of a computer, you can
plot is using a graphing paper
lj chart
- Referring to values that either increase or decrease for six
consecutive days - Caused by deteriorating reagent or changes in the
concentration of standards.
trend
Formed by control values that distribute themselves on one
side or either side of the mean for six consecutive days
- Usually caused by improper calibration in the instruments,
changes in the reagent or sudden change in performance or
procedures
shift
- Values far from the main set of values
- Highly deviating values
- Can be a random or systematic error
outliers
Use of high-grade equipment
- Careful use of the equipment
are correction for what error?
random errors
- Lead to the formation of outliers /requires statistical
techniques to be rejected
GROSS ERROR / BLUNDERS
Spilling of small portions of sample during the transfer of
liquids to the container
“Overrun endpoint”
instrument breakdown
loss of crucial sample
are example of what error
gross error / blunders
Precipitation of impurities
Impurities of reagent unstable specimen
Side reactions
Slow or incomplete reactions
are examples of what error
methodoic error
- One value exceed the 3SD
- Indicates Random Error
13S Criteria for Violation
- One of the values exceed the 2SD
- Indicates Random Error
12S
Rejection when the last two control results exist either the
mean positive or negative 2SD
* Indicates Systematic Error
22S VIOLATION
the shorter the wavelength, the higher the ??
frequency
E= hv (h – constant; v - freaquency)
PLANCK’S FORMULA
- Most common type of photodetector
- Excellent sensitivity and rapid response
Photomultiplier (PM) tube
