B - CHAPTER IV: QUALITY CONTROL IN CLINICAL CHEMISTRY Flashcards
– a degree to which a set of inherent characteristics fulfills requirements (ISO 9001:2008)
QUALITY
- part of quality management focused on fulfilling quality requirements (ISO 9000:2000)
QUALITY CONTROL
• System of assuring the quality of total laboratory performance
QUALITY CONTROL
• Involves the periodic systematic surveillance of people, tools, methods and reagents
QUALITY CONTROL
– part of quality management focused on providing confidence that the quality requirements will be fulfilled (ISO 9000:2000)
QUALITY ASSURANCE
- Set of activities or plan that aims to maintain the highest degree of excellence for the diagnosis & treatment of disease and maintenance of health
QUALITY ASSURANCE PROGRAM
AREAS of QUALITY CONTROL:
- All [?] are involved.
- The laboratory’s relation to other [?]
- Laboratory [?] should be collected in a manual to be revised at least once a year or when procedures are changed.
patients, laboratory personnel, laboratory equipment, and laboratory tests
hospital departments
policies and procedures
SYSTEM CONCEPTS of QUALITY CONTROL:
– establishes norms that must be met
- Quality Control Surveillance System (QCCS)
– established to offer education of why errors occur; provide a program to remedy defects
- Q.C. Corrective System
– established to prove that corrective measures have produced favorable results.
- Objective Q.C. Parameters
PROCEDURES in QUALITY ASSURANCE PROGRAM
A. CONTROL of PRE-ANALYTICAL VARIABLES FACTORS:
B. CONTROL OF ANALYTICAL VARIABLES MAIN FACTORS:
- Choice of analytical methodology
- Calibration procedures
- Proper documentation of analytical variables
- Proper labeling & use of reagents
- Preventive maintenance of analytical instruments
- Periodic calibration of pipetting devices
- Periodic checking of °T of refrigerator & heating units
- Periodic checking of procedure manuals
- Monitoring of technical competence
- Inventory of control materials
- Control assurance that safety measures are operational
C. CONTROL of POST-ANALYTICAL VARIABLES FACTORS:
- Verification of calculations of the final results
- Check test results for possible transcription errors
- Results should be easy to read & interpret
- Timeliness of reporting values to patient chart
- Procedures for informing physicians about results that require immediate attention
FACTORS Involved in QUALITY CONTROL
- STANDARD
- CONTROL MATERIAL
o A substance of known composition
STANDARD
o Its value is established by an analytical procedure different from that used in the clinical laboratory
STANDARD
o A substance which resembles the unknown specimen (patient’s sample)
CONTROL MATERIAL
o Analyzed daily together with the unknown
CONTROL MATERIAL
o The values obtained from the assays are used for the computation of the mean and the SD
CONTROL MATERIAL
Types of Control Material:
a. Commercial Control Sera
b. Pooled Sera
- are collected daily in the laboratory and pooled for storage in the refrigerator
Excess non-hemolyzed sera without gross lipemia
- When [?] are collected, centrifuge to remove gross contamination
1 – 2 liters
- Filter and divide into aliquots of [?] each
5 mL
- Stopper and store at
-20°C
- [?] as needed and mix well before use
Thaw
ELEMENTS of QUALITY CONTROL:
– extent to w/c the measurement approximates the true value of the quantity being measured
ACCURACY
– a.k.a reproducibility; degree to w/c repeated results agree to each other
PRECISION
– ability of a method to detect a particular substance w/o the interference of some other substances present in the sample
SPECIFICITY
– ability of a method to detect even the smallest amount of that particular substance tested for
SENSITIVITY
– ability of a method to maintain its accuracy & precision over an extended period of time 6. PRACTICABILITY – degree to w/c the method is easily repeated
RELIABILITY
STATISTICAL CONCEPTS in QUALITY CONTROL
➢ A statement of the extent of random variation in any series of measurement
STANDARD DEVIATION
➢ A measure of the distribution of values around the mean
STANDARD DEVIATION
Square of the standard deviation
VARIANCE (s2)
Used to detect significant differences between groups of data
VARIANCE (s2)
Determine contributions of various factors to the total variation
VARIANCE (s2)
Percentile expression of the mean
COEFFICIENT OF VARIATION
Measure of the relative magnitude of variability
COEFFICIENT OF VARIATION
QUALITY CONTROL Associated Activities:
- Assay of control samples
- Instrument maintenance
- Statistical Data Analysis
- Proficiency testing survey
ASPECTS which the laboratory should avoid or minimize:
- Analytical Bias
- Random Analytical Variability
3.ERRORS
❖ Reported values do not fall along the line of slope when graphed
Analytical Bias
❖ Reported lab results do not correspond to the correct value
Analytical Bias
Types of Analytical Bias:
a) Proportional bias
b) Constant bias
c) Combined bias
Problem on Accuracy (Bias) =
Systematic Error
Refers to laboratory analyses that are subject to imprecision
Random Analytical Variability