Reference Interval Flashcards
Reference value
is a term used in medicine to denote a laboratory value used as a reference for values obtained by laboratory examinations of patient samples (blood, urine or other materials)
T/F
T
A reference range
-is a set of reference values used by a health professional to interpret a set of medical test results.
T/F
T
A reference range
The range is usually defined as the set of values that ___% of the healthy population falls within
95
Reference individual:
-An individual selected for comparison using defined criteria
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T
Reference Value:
-observation/measurement of a quantity on a reference individual
T/F
T
Observed value:
-value of a particular quantity obtained by observation/measurement & produced to make a medical desicion
T/F
T
Relationship of Recommended Terms
Reference ___ make up a Reference Population from which is selected Reference ____on which Reference ____ are determined
on which is observed a Reference ___ on which are calculated Reference ___ that may define Reference Intervals
individual
Sample Group
Values
Distribution
Limits
Types of Reference Ranges
-___ based reference ranges
-____ associated reference ranges
-_____ based reference ranges
-____ Specified ranges
Subject
Health
Population
Time
Subject based reference ranges
-Comparison of _____
-Often more sensitive in that it rules out ______
an individuals current value with an historical one
biological variation effects.
Biological factors
Age: e.g. (higher or lower?) plasma urea levels are found in the elderly. Also , (higher or lower?) ALP activity in growing children compared with adults.
Higher
Higher
Sex: e.g. (higher or lower?) values of plasma urea, creatinine and urate are found in men
compared with women during the
reproductive phase of life.
Higher
serum iron levels (rise or declines ?) as the day progresses.
Rise
plasma protein levels are (higher or lower?) in samples collected from patients when they are lying down.
Lower
Determination of Reference Limits
-Mean ____ – Parametric statistic for
Gaussian or normal frequency distribution
-_____– Non-Parametric statistic for
Skewed or Non-Gaussian distribution
-Log transformation of data for Skewed or
Non-Gaussian distribution – Mean ± 2SD
± 2SD
Percentiles
Unit:______
Sodium-
Potassium-
Bicarbonate-
Mmol/L
135-145
3.3-5.0
18-31
Unit:_____
Calcium-
Phosphate-
Magnesium-
Mmol/L
2.1-2.55
0.83-1.48
0.66-1.07
Unit: ______
Chloride-
UREA-
Blood urea nitrogen-
Mmol/L
95-105
2.5-6.4
1.7-9.1
Creatinine in serum (___) - _____
Creatinine in 24hr urine( ___)-____
Umol/L
53-115
Mmol/day
7.1-17.1
Unit:_____
Fasting plasma glucose:
Random plasma glucose:
Mmol/L
3.5-5.8
3.6-7.8
Total bilirubin(____)?
Umol
1.7-17.1
Creatinine clearance( _____) -??
Ml/min
90-125
Conjugated bilirubin (—-)-?
Umol/L
0-3,4
Reference intervals are sometimes erroneously referred to as “ _______.”
normal ranges
all normal ranges are reference intervals
T/F
T
all reference intervals are normal ranges.
T/F
F
Reference intervals , reference ranges
the preferred term is ___________
Why?
reference interval
because range implies the absolute maximum and minimum values
The clinical laboratory is required by good laboratory practice and accreditation agencies (i.e.,____________ checklist) to either _______ or _____ reference intervals for any new tests or significant changes in methodology.
College of American Pathologists [CAP]
verify or establish
Establishing a reference interval
It is a costly and labor-intensive study that will involve laboratory resources at all levels and may require from ____ to as many as >___ study individuals.
120
700
Verifying a reference interval
Verifying a reference interval (______): This is done to confirm the validity of an existing reference interval for an analyte using the same (identical) type of analytic system (method and/or instrument).
These can require as few as ___ study individuals
transference
20
most common reference interval studies performed in the clinical laboratory is??
Verifying a reference interval
Verifying a reference interval
The manufacturer’s reported 95% reference limits may be considered valid if no more than ___% of the tested subjects fall outside the original reported limits
If more than __% of the values fall outside of the proposed interval, an additional ____ or more specimens should be analyzed.
If the second attempt at verification fails, the laboratorian should re-examine the analytic procedure and identify any differences between the laboratory’s population and the population used by the manufacturer for their analysis.
If no differences are identified, the laboratory may need to establish the reference interval using at least ______ individuals.
Once a reference interval is determined, it needs to be communicated to the ____________
This is important given the slight variations in reference intervals seen even among testing facilities using similar methodologies.
10
10
20
120
physicians interpreting test results at the time the test results are reported.
Use histogram or bar chart?
Histogram
In the most basic sense, data may be either normally distributed (_____) or skewed (_____)
gaussian
nongaussian
gaussian or _______ or _______ or ______
Normal distribution curve
Frequency distribution curve
Bell’s curve
A parametric method defines the interval by the mean +/-___ SDs; this formula will include the central 95% of values as given in the example shown.
1.96
In reality, most analytes display a normal (gaussian) distribution.
T/F
F
They do not
Data that are not normally distributed (i.e., nongaussian) must be analyzed using _______ analyses.
nonparametric
Nonparametric determination of the reference interval is analyzed using ______, which (do or do not?) depend on the distribution.
percentages
Do not
For nonparametric
The reference interval is determined by using the central 95% of values; the reference range is therefore defined by the ____ to the ____ percentiles.
2.5th
97.5th
Most reference interval analyses are determined using (parametric or nonparametric?) analysis.
This is because (parametric or nonparametric?) analysis can be used on (gaussian or skewed ?) distributed data and it is the ____-recommended method
nonparametric
nonparametric
gaussian
CLSI
three most commonly used descriptions of the center are the ______,_____, and _____
The _____ is most commonly used and often referred to as the ______
The _____ is the “middle” point of the data and is often used with (Gaussian or skewed ?) data.
The ______ is rarely used as a measure of the data’s center but is more often used to describe data that seem to have _____
mean, the median, and the mode.
mean; average
median;skewed
mode; two centers (i.e., bimodal).
In other words, given any gaussian distributed data:
Approximately ____% of the data fall between +/-1 SD from the mean;
Approximately ____% of the data fall between +/-2 SDs from the mean; and
Approximately ____% fall between +/- 3 SDs from the mean.
68
95
99
When interpreting laboratory data, clinicians compare the measured test result from a patient with a _______
reference interval.
The theory for the development of reference intervals was the work of _____ main expert committees.
two
Reference intervals are usually established by the _________ or the ___________ and new methodologies.
scientific community
manufacturers of reagents
_________________ is an example of an accreditation agency
College of American Pathologists [CAP] checklist
Answer with pre-analytical or analytical considerations
Subject preparation
Stress
pre-analytical
pre-analytical
Answer with pre-analytical or analytical
Collection time
pre-analytical
Answer with pre-analytical or analytical
Prescription medications
Pre-analytical
Answer with pre-analytical or analytical
Sample storage
Precision
Pre-analytical
Analytical
Answer with pre-analytical or analytical
Food/beverage ingestion
pre-analytical
Answer with pre-analytical or analytical
Accuracy
analytical
Answer with pre-analytical or analytical
Linearity
Recovery
analytical
analytical
Answer with pre-analytical or analytical
Interference
Analytical
Answer with pre-analytical or analytical
Lot-to-lot reagents
Analytical
The reference interval is calculated statistically using methods that depend on the __________
distribution of the data.
Nonparametric determination of the reference interval is analyzed using _____
percentages
Nonparametric curve depends on the distribution of data
T/F
F
It doesn’t
There are three most commonly used descriptions of spread: (1) ____, (2) ______, and (3)___________.
range
Standard deviation(S.D)
coefficient of variation (CV)
The total area under the gaussian curve is ___, or ___%.
1.0
100
