- range - SD - coefficient of variation - SD index

POC testing Flashcards by Ruth Joy De Guzman

What are the measure of center

mean
median
mode

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most commonly used and often called the
average

mean

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: is the “middle” point and is often used with
skewed data so its calculation is not significantly affected
by outliers.

median

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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

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The foundation for monitoring performance
(known as QC

descriptive statistics

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imply the largest value in the
data minus the smallest value, which
represents the extremes of data one might
encounter.

range

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most frequently used measure of
variation

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most frequently occurring value in a
data set. Although it is seldom used to describe data,
it is referred to when in reference to the shape of
data, a bimodal distribution

mode

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MEASURE OF SPREAD

range
SD
coefficient of variation
SD index

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similar to the mean in that it
is an average.

variance

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calculated by dividing the SD by
the mean and multiplying by 100 to
express it as a percentage

coefficient of variation

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the average of the squared
distances of all values from the mean

variance

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A solution of known characteristics and of
known value or whose concentration is
accurately known

standard solution

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Serve as a reference for unknown

standard solution

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For precision

CONTROL SOLUTION

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For accuracy

standard solution

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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

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It sets the spectrophotometer
reading to zero

blank solution

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The fundamental basis of any statistical
analysis

Machine problems
Contaminated reagent
Technical errors

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Distilled water as reagent blank
vs Specific reagent per analyte

blank solution

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A solution composed of several known constituents which can be run simultaneously with the test to check the accuracy of the results.

control solution

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The mathematical result when the summation
of data is divided by the total number of data

Arithmetic Value or Mean or average (x)

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It is the percentile expression of the mean which is measure of the relative magnitude of variability.

Coefficient of Variation (CV)

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Stable for a long period of time

control solution

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It is the statement of the extent of variation in any series of measurement

It is the ratio of the standard deviation over the mean expressed in percent

It is a measure of the distribution range of values around the mean value or average

It is a statement of variability and measures the significant differences between groups of data

Variance

Example of histograms

- Shewhart-Levey Jennings Chart - Gaussian Curve - Cumulative Sum Graph -Youden Plot

It will group any series of measurement in the same sample in a cluster around the mean in a bell shaped curve

Gaussian Curve

Most commonly used quality charts or histograms

Shewhart-Levey Jennings Chart

with x and y axis

Youden Plot

value is zero and not the mean.

Cumulative Sum Graph

Cumulative Sum Graph also known as

CUSUM graph

Gaussian Curve also known as

Gaussian distribution curve, normal distribution curve and commonly the bell-shaped curve

also known as dot chart

Shewhart-Levey Jennings Chart

Shewhart-Levey Jennings Chart also referred as

Levey-Jenning chart, S-L/J

Plotted with the accumulated differences from the mean of individual values with the middle value being zero.

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.

Youden Plot

uses a multiple QC procedure as decision criteria to determine if an analytic run is in control

Westgard rules

Youden Plot also referred as

Twin plot, Two-Mean chart or the Two-way Average chart

WESTGARD RULES definiton

- Reduces false rejections and maintains high error detection - Provides help in troubleshooting

when the values of the control fall within the confidence limit

In control

when the values of the control fall outside the confidence limit.

out of control

Violation of this rule is associated with random error

1 3s

The numerical difference between this 2 controlled values within the same run exceeds 4 SD

R 4s

Serves as a warning rule that will alert the med tech for possible problem`

1 2s

States that 4 consecutive controlled values exceeds ± 1 standard deviation and on the same side of the mean

4 1s

controlled value is greater than - 2 SD; other value exceeds + 2 SD

R 4s

States that 1 controlled value exist ± 2 standard deviation from the mean

1 2s

1 controlled value exceeds ± 3 standard deviation from the mean.

1 3s

Violation of this rule is associated with systematic error

10 X

2 consecutive controlled values exceed the same limit, either +2SD or -2SD

2 2s

formed by controlled values that is either increase or decrease for at least 6 consecutive days

trend

Formed by controlled values that distribute themselves on one side of the mean for at least 6 consecutive days

shift

This indicates a gradual loss of reliability in the test system

trend

Represents sudden or abrupt change in the test system performance

shift

Set of numbers indicating range and values one would expect in a defined population with no apparent clinical problems

reference value

defined as medical testing at or near the site of patient care.

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

It is important to establish a structure for POCT that defines authority, responsibility, and accountability

Oversight structure

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 made.

point of care testing

purpose of structure for POCT

To facilitate timely and accurate performance. To facilitate compliance with regulatory agencies. To facilitate a process of standardization. To coordinate and facilitate communication between the laboratory. To facilitate the education of POCT personnel.

a laboratory scientist or pathologist with a PhD, MD, or DO degree usually fills this position

director

for each units/floor/clinic that performs POCT, it is important to have a designated contact person or trainer. This person greatly facilitates the efficient POCT program and is a communication link between the POCC and the testing staff

designated contacts

responsible for implementing and coordinating point- of care patient testing and facilitating compliance with procedures and policies and regulatory requirements

Point-of-care coordinator

Validation

Accuracy

– Sensitivity and specificity – Reportable range/linearity – Reference range – Split-sample correlation vs reference method

precision

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

The following materials should be collected before beginning the implementation process:

 Instrument manual  Package inserts for reagent  Package inserts for quality controls  Materials safety data sheet  Sample procedure from vendor  Sample training materials from vendor  Other institutions procedure for test  Applicable regulatory or certifying standard

Procedure/Policy

 ▪ Principle  ▪ Testing personnel  ▪ Specimen  ▪ Reagents  ▪ Reagents, supplies, and equipment  ▪ Maintenance  ▪ Power  ▪ Calibration  ▪ Quality control

Training Checklist

 ▪ Read procedure  ▪ Maintenance  ▪ Reagents  ▪ QC  ▪ Specimen requirements  ▪ Direct observation  ▪ Reporting results  ▪ Safety  ▪ Operator information (name, operator ID no., floor)  ▪ Trainer signature  ▪ May supplement with quiz

most frequently electrolytes and/or blood gases

Point-of-care chemistries and blood gases

connectivity has been the most significant recent development in POCT.

Point-of-care connectivity

is the highest volume POC test in most healthcare institutions

Point-of-care glucose

the most common POC coagulation test is activated clotting time (ACT)

Point-of-care coagulation

at the present time, only minimal hematology POCT has been available. The spun hematocrit was the most common POC hematology test

Point-of-care hematology