Method Eval Flashcards
The measure of center, spread and shape.
Descriptive statistics
Assessment of data dispersion, or spread, allows
laboratorians to assess the predictability (and the
lack of) in a laboratory test or measurement.
Descriptive statistics
Most commonly used and often measure
Mean
Mean is also called as
Average
Add all the given value, then divide it to the number of the values
Mean
is used in many statistical
formulas.
Summation sign
the mean of a specific dataset is
called
X or x bar
The “middle” point and is often used with skewed
data so its calculation is not significantly affected
by outliers.
Median
It is the middle of the data after the data have been
rank ordered.
Median
It is the value that divides the data in
half.
Median
values are rank ordered
from least to greatest and the middle value is
selected.
Median
Rarely used as a measure of the data’s center but is
more often used to describe data that seem to
have two centers
Mode
Mode is also called as
Bimodal
is the most frequently occurring value in
a data set.
Mode
it is seldom used to describe
data
Mode
it is referred to when in reference to the
shape of data, a bimodal distribution
Mode
it is referred to when in reference to the
shape of data, a bimodal distribution
Mode
There are four commonly used
descriptions of spread:
Range
Standard deviation
Coefficient of variation
Standard deviation index
It is a common type of distribution for variable
Bell curve/ normal distribution/ gaussian curve
The easiest measure of spread to understand
Range
is simply the largest value in the data
minus the smallest value, which represents the
extremes of data one might encounter.
Range
is often a good measure of dispersion
for small samples of data.
Range
is one description of the spread of data.
Range
It is simply
the difference between the highest and lowest data
points
Range
To calculate the SD of a dataset, it is easiest to first
determine the variance
Variance
is similar to the mean in that it is an
average.
Variance
is the average of the squared distances of
all values from the mean:
Variance
- is the most frequently used measure of variation.
Standard deviation
is the square root of variance
Standard deviation
Standard deviation is called
s, SD or σ
Another way of expressing SD is in terms of the
Coefficient of variation
is calculated by dividing the SD by
the mean and multiplying by 100 to
express it as a percentage:
Coefficient of variation
Formula of Coefficient of variation
CV= (SD/M)x 100
the __________ the STANDARD DEVIATION (SD) is and
the LOWER the COEFFICIENT OF VARIATION (CV) is,
the MORE PRECISE the data is.
LOWER
the LOWER the STANDARD DEVIATION (SD) is and
the LOWER the COEFFICIENT OF VARIATION (CV) is,
the MORE ___________ the data is.
PRECISE
preferably used to determine errors/variations
Levey-Jennings Chart
Solution For accuracy
Standard solution
A solution of known characteristics and of known
value or whose concentration is
accurately known
Standard solution
It is composed of one known constituent only and
used as a basis of reference for the calculation of
the value of the unknown.
Standard solution
100% pure solution
Standard solution
Serve as a reference for unknown
Standard solution
Choose the standard nearest to the unknown
Standard solution
purity of standard solution
100% +0.02%
Concentration of the unknown
Standard solution
For precision solution
Control 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.
Control solution
Stable for a long period of time
Control solution
2 forms control solution
Liquid or lyophilized
WHEN TO PERFORM
QUALITY CONTROL
- Beginning of each shift (Daily testing)
- New instrument
- After an instrument is serviced
- When reagent lots are changed
- After calibration and
- Whenever patient results seem inappropriate
*Lot number changes annually
*Calibration must be followed by control
A solution without the specimen.
Blank solution
It sets the spectrophotometer reading to zero.
blank solution
Distilled water as reagent blank
vs. Specific reagent per analyte
Blank solution
Three types blank solution
Water blank
Sample blank
Reagents blank
Type of Blank solution remove interference
Sample blank
e.g. of interference sample balnk
Hemoglobin - hemolysis
Lipid- turbidity
Bilirubin- increase
Type of blank solution set reading to zero, for
correcting color interference
Reagent blank
Errors in Quality Control
Variation
The fundamental basis of any statistical analysis.
Mechanial problems
Contaminated reagent
Technical errors
The mathematical result when the summation of data is divided by the total number of
data
Arithmetic value or mean or average
It is the statement of the extent of variation in any series of measurement
Standard deviation
It is a measure of the distribution range of values around the mean value or average
Standard deviation
Measure of spread of data.
Standard deviation
It is the percentile expression of the mean which is measure of the relative magnitude of
variability.
Coefficient of variation
- It is the ratio of the standard deviation over the mean expressed in percent
Coefficient of variation
It is a statement of variability and measures the significant differences between groups of
data.
Variance
Most commonly used histogram/charts
Shewhart-levey jenning chart
Shewhart-jevey jenning chart also known as
Levey-jenning chart, s-l/j or dot chart
It will group any series of measurement in the same sample in
a cluster around the mean in a bell shaped curve
gaussian curve
Histogram show the confidence limit
Gaussian curve
Gaussian curve also known as
Gaussian distribution curve, normal
distribution curve
Gaussian curve is commonly known as
Bell-shaped curve
Plotted with the accumulated differences from the mean of
individual values with the middle value being zero.
Cumulative sum graph
Value is zero and not the mean.
Cumulative sum graph
Cumulative sum graph also known as
Cusum graph
Histogram/chart with x and y axis
Youden plot
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.
Youden plot
Youden plot also known as
Twin plot, two mean chart or two way average chart
INTERPRETATION OF RESULTS: when the values of the control fall within the confidence limit
In control
INTERPRETATION OF RESULTS: when the values of the control fall outside the confidence limit.
Out control
Westgard rule Developed by
James westgard
uses a multiple QC procedure as decision criteria to
determine if an analytic run is in control
Westgard rules
States that 1 controlled value
exist ± 2 standard deviation from the
mean.
1 2 s
Serves as a warning rule that
will alert the med tech for possible
problem
1 2s error
States that 1 controlled value
exist ± 2 standard deviation from the
mean.
1 2s error
States that 4 consecutive controlled
values exceeds ± 1 standard deviation
and on the same side of the mean
4 1s error
2 consecutive controlled values
exceed the same limit, either +2SD
or -2SD
2 2s error
1 controlled value is greater than - 2
SD; other value exceeds + 2 SD
R 4s error
The numerical difference
between this 2 controlled values
within the same run exceeds 4 SD
R 4s error
10 consecutive controlled
value lies in the same side of the
mean
10x error
No requirement as to the size of SD
10x error
Violation of the rule
is associated with: 1 2s error
None
Violation of the rule
is associated with: 1 3s error
Random error
Violation of the rule
is associated with: 4 1s error
Systematic error
Violation of the rule
is associated with: 2 2s error
Systematic error
Violation of the rule
is associated with: R 4s error
Random error
Violation of the rule
is associated with: 10x error
Systematic error
is formed by controlled
values that is either increase or
decrease for at least 6 consecutive
days
Trend
This indicates a gradual loss of
reliability in the test system
Trend
Formed by controlled values that
distribute themselves on one side of
the mean for at least 6 consecutive
days
Shift
Represents sudden or abrupt
change in the test system
performance
Shift
Trend main cause
deterioration of
reagent
Shift main cause
improper calibration
of machine
Range of values for a given constituent in healthy individuals (normal value)
Reference value
Set of numbers indicating range and values one would expect in a defined population with no apparent clinical problems
Reference value
Concept of Gaussian distribution can be directly applied to the discussion of reference values
Reference value
POINT OF CARE TECHNIQUE
Objectives:
– 1. Define point of care testing
– 2. Explain what basic structure is required to manage POCT team
– 3. List the common POC applications
is defined as medical testing at or near the site of patient
care.
Point of care testing
The driving notion behind POCT is to bring the test conveniently and immediately to the
patient.
Point of care testing
This increases the likelihood that the patient, physician, and care team will receive the
results quicker, which allows for immediate clinical management decisions to be mad
Point of care testing
POCT includes:
-blood glucose testing,
-blood gas and electrolytes analysis,
-rapid coagulation testing,
-rapid cardiac markers diagnostics,
-drugs of abuse screening,
-urine strips testing, etc.
Support staff:
- Director
- Point-of-care coordinator
- Designated contacts or trainers in
non-laboratory departments
a laboratory scientist or pathologist with a PhD, MD, or DO degree usually
fills this position.
Director
the POCC coordinator is responsible for implementing and coordinating
point- of care patient testing and facilitating compliance with procedures
and policies and regulatory requirements.
Point of care coordinator
for each units/floor/clinic that performs POCT, it is important to have a
designated contact person or trainer.
Designated contacts or trainers in
non-laboratory departments
This person greatly facilitates the efficient POCT program and is a
communication link between the POCC and the testing staff
Designated contacts or trainers in
non-laboratory departments
Is the consistent use of the same instrument/reagent/test method for any particular
analyte throughout the designated health care system
Standardization
Standardization produces the following benefits:
> Improved patient care
Decrease cost
Saves work in time
Facilitates regulatory compliance
Committees Communication:
Networking
Committees Selection of device and methods:
review multiple options
Implementation
o Instrument manual
o Package inserts for reagent
o Package inserts for quality controls
o Materials safety data sheet
o Sample procedure from vendor
Procedure/Policy
• Principle
• Specimen
• Reagents
• Maintenance
• Power
Training Checklist
▪ Maintenance
▪ Reagents
▪ QC
▪ Reporting results
▪ Safety
Point-of-care applications
Point-of-care glucose
Point-of-care chemistries and blood gases
Point-of-care coagulation
Point-of-care hematology
Point-of-care connectivity
is the highest volume POC test in most healthcare institutions.
POC glucose
- most frequently electrolytes and/or blood gases.
POC blood gas
- the most common POC coagulation test is activated clotting time (ACT)
POC coagulation
POC coagulation - the most common POC coagulation test is _______________ (ACT)
activated clotting time
- at the present time, only minimal hematology POCT has been available.
POC hematology
The spun hematocrit was the most common POC hematology test.
POC hematology
was the most common POC hematology test.
spun hematocrit
connectivity has been the most significant recent development in POCT.
POC connectivity
Accuracy under only
Validation
Precision under
– Sensitivity and specificity
– Reportable range/linearity
– Reference range
– Split-sample correlation vs reference method
