Reagents and reference materials Flashcards
(20 cards)
Chemistry approach
Machine used: Cobas
Liquid reagent: No constitution needed; ready to use and shorter shelf life
WET CHEMISTRY
- Needs a reconstitution reagent (distilled water); Used for controls, standards or calibrators, and reagents
- Process of adding distilled water to lyophilized reagent
- Product:
- Advantage over compared to liquid
- Lyophilized
- Reconstitution
- Reconstituted reagent
- Longer shelf life
- Entails freezing a material at −40 °C or less and then subjecting it to a high vacuum
- Very low temperatures cause the ice to sublimate to a vapor state
- The solid non-sublimable material remains behind in a dried state
Lyophilization
- Machine used: Vitros; Features a smaller volume requirement, less error
- Reagent preparation is not required because of?
- Principle used (based on 1):
- Dry chemistry
- cartridge (less time preparation)
- Reflectance photometry
Remember the 5 layers
SSRIS
1. Spreading layer
2. Scavenger layer
3. Reagent layer
4. Indicator layer
5. Support layer
- Reagent reacts with sample
- Reacted sample collects for spectral analysis
- Optical interface
- Sample is distributed evenly
- Filters out substances that interfere with
results
A. Spreading layer
B. Scavenger layer
C. Reagent layer
D. Indicator layer
E. Support layer
CDEAB
REAGENT CONSIDERATIONS
- Check the label
- See expiration date
- Check reagent lot number
- Write date opened & initials of MT
STORAGE AND STABILITY
- If there is change in the reagent lot number perform
- Reagent storage
- Trend/Drift shows what error?
- 4 reasons for using a calibrator/standard
- Validation study (recalibration)
- 2-8C
- Systematic
- Change in the reagent lot number (1), rgt control out of range (2), for eval & technical validation (3), and when establishing a reference range (4)
INTERFERING SUBSTANCES
- Interferes most of the reaction especially if its enzymatic principle
- In clinical chemistry test, what specimen is always used?
- Common interference:
- TOF. Drugs and other substances absent in the sample
- TOF. Diliuent water with microbial group
- Anticoagulants
- Serum
- EDTA, sodium flouride, potassium oxalate
- False (presence)
- True (Pyridoxal phosphate)
- Also called intra-assay precision, this measures how consistent test results are within a single run (no time gap).
- It assesses repeatability—how close the results are when the same sample is tested multiple times in one session.
- Repeatability in one run
Within-run precision
Run 1 at 6 AM:
Result 1 = 10
Result 2 = 10
Result 3 = 10
…
Interpretation: If all values are nearly identical, the within-run precision is excellent.
- Also called between-run precision, this checks consistency of test results over multiple runs with time gaps.
- It’s about reproducibility over time—like checking if the analyzer gives consistent results for the same sample when tested at 6 AM, 1 PM, and 6 PM.
Run-to-run precision
REFERENCE MATERIALS
- Substance of lower purity; Cannot be used alone, this requires the main standard.
- Represents a specimen that is similar in composition to the patient’s whole blood or plasma. The value is known and measured the same way with the patient unknown sample.
- A highly purified chemical can be measured directly to produce a substance of exact known concentration; Can be used alone
- Value is predetermined by manufacturer
- Medtech determined the value
A. Primary standard
B. Secondary standard
C. Controls
D. Assayed
E. Unassayed
- B
- C
- A
- D
- E
CONTROLS
● Normal or pathological
● Use of control is once in 24 hours
● Westerguard rules:
- 1:2S
- 1:3S
- R:4S
- 2:2S
- 4:1S
- 10:X
2 Levels
Westgard rules for 2 levels
● Westerguard rules:
- 1:2S
- 1:3S
- R:4S
- 2:2S
- 4:1S
- 10:X
● High, normal, or low
● Use of control is every 8 hours
● Blood gasses
● POCT glucose
● Additional westgard rules :
- 3:15
- 2 of 3:2S
- 7T
- 9X
3 Levels
additional westgard rules of 3 levels
● Westerguard rules:
- 1:2S
- 1:3S
- R:4S
- 2:2S
- 4:1S
- 10:X
● Additional westgard rules :
- 3:15
- 2 of 3:2S
- 7T
- 9X
Control
- All tests for clinical chemistry only use 2 levels of control except:
- Tests that are obligate to use control every 8 hours:
- blood gasses, therapeutic drugs and hormones
- blood gasses, POCT for glucose and for CBC
● Monitors overall reliability of laboratory results
● By means of accuracy and precision :
QUALITY CONTROL
TWO DIVISIONS OF QUALITY CONTROL
- Analysis of control samples; Instrument maintenance; Statistical analysis
- Proficiency testing or NEQAS (National
External Quality Assurance Team
- Internal
- External
Reference Lab
- Clinical chemistry
- Hematology
- Cardiovascular markers
- MicroPara
- HIV
- Lung center of the Philippines
- NKTI
- Heart Center
- RITM
- San Lazaro SACCL
