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Total Allowable Error (TEa).pptx
1. Total Allowable Error (TEa)
or
Allowable Total Error( ATE)
Labs for Life Project
QUALITY CONTROL TRAINING
2. What is a Quality
Specification/ requirement?
Quality requirements care set to help
guide interpretation of laboratory test
results because they
◦provide perspective about variability of
results within an acceptable interval
◦potential significance of abnormal findings
3. What are some Quality
Specifications?
Total Allowable Error (TEa) which is derived for
clinical decision thresholds is a very useful Quality
Specification that can be adopted for labs: TE< TEa
Sigma-metrics, to define the tolerance limits: Labs
may adopt sigma rules in their quality
specifications (CLSI C 24 A3) (discussed later)
DPMO (Defects per Million Occasions)
5. What is and Why TEa?
Total Allowable Error (TEa) is the amount of
error that can be tolerated without
invalidating the medical usefulness of the
analytic result.
Knowing the Total Error in a system will be of
clinical use only if there is benchmarking for
the allowable error for that analyte.
7. Medical Decision Requirements:
Very few analytes are thus defined
NGSP: National Glycohemoglobin Standardization Program (NGSP)
TEa of HbA1c <6%
NCEP: National Cholesterol Education Program
TEa of Cholesterol < 9%, HDL < 13%, LDL <12%,
Triglyceride <15%
8. Biological Variation Database
The natural fluctuation of body fluid constituents
around the homeostatic setting point, has two
components: within and between-subject variation.
These have been used for many purposes
oTo set analytical quality specifications (As used here)
oTo evaluate the significance of changes in serial results
oTo assess the utility of population-based reference values
oTo assess the number of specimens required to estimate
the homeostatic set point
oTo assess the clinical utility of tests
10. Biological Variation: 3 Databases
The lab may adopt any as their guidelines
Minimum
Desirable
Optimum
11. CLIA Proficiency Testing
Guidelines
Performance goals set by organizers of external
proficiency assessment programs (e.g. CLIA)
In order that QC procedures can ascertain stable
equipment performance, CLIA has prescribed the
TEa limits on deviations from the observations in
the PT program and as per the criticality of the
analyte.
CLIA specifies the goal as percentages or ±
absolute values at the target or as ± 3 SD or a
combination
14. CLIA Proficiency Testing Limits
In the absence of any guideline,
the lab may use the earlier PT
reports.
In the example, for the CD 4
count, the average CV% is 5%.
Three times this is 15%. This
may be applied as the % TEa.
A count of 100 cells, an
acceptable would be ± 15.
Alternatively the lab can use
the respective percent against
the level.
15. Tonk’s Rule
TEa = 25% * BRI as per Tonk’s rules.
Subtract the lower end of reference range from the upper
end and divide by 4 for the absolute number or derive the
percent with the target value as the denominator.
◦ (UL- LL)/ 4 = Absolute TEa
◦ {(UL- LL)/Target}*100 = % TEa
Disadvantages
TEa from reference intervals are also referred to in CLIA ’88
rules which suggests 50% * BRI. This gives rise to
considerable problems
The reference intervals are lab defined, often revised.
16.
17. Current (Running) CV*3
As a last resort, the Current (Running) CV can
be taken as a guideline.
3 times the CV will not only accommodate
the random error, but account for the SE also.
