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Quality Control: Clin Path
Terms in this set (39)
items that contribute to quality control
Entire process in which all phases of lab testing are considered. Goal is to build in quality as part of the testing process to assure test results are correct. Includes planning, monitoring, and education.
A part of quality assurance. Goal is to show that the testing system is operating within acceptable limits and the results are accurate. It uses basic statistical analysis and other analyses to determine that equipment, reagents, and operators are functioning correctly.
Clinical Laboratory Improvement Act of 1988. In human clinical labs, valid QC procedures for instrumentation must be in place. Vet clinic labs have no overall regulation except AAHA guidelines (in some clinics- individual clinics have their own guidelines).
NDSU Diagnostic Lab- has a quality assurance program in place as required by the American Association of Veterinary Laboratory Diagnosticians (the accrediting body for the lab).
1. Routine clin path services must be provided in the hospital lab or through outside sources.
2. A list of services that must be available is given (hematology, serology, chemistry, etc.).
3. Reference ranges must be available for all lab tests performed by both in- house and external labs.
4. Instrumentation for tests performed on the premises must be adequate and include certain minimum equipment.
5. For tests done in external labs, certain info must be supplied (data from specimen, date of sample collection, etc.).
quality control program- AAHA
1. All in-house lab services performed must be carried out by competent personnel using approved standard lab procedures. The quality control system within the pathology lab must be designed to ensure medical reliability of lab data.
2. For in-hospital lab procedures, equipment must be operated and evaluated according to the manufacturer's recommendations and have a written protocol of operation.
3. A record of the quality control tests and maintenance procedures performed on all lab equipment must be maintained.
4. For outside lab procedures, a current letter from the outside lab must be available assuring that a quality control program is in effect. They should participate in at least an annual proficiency survey/ reference sample services covering all types of analyses performed to verify competence.
vet clinics- state of affairs
QC was often not routinely done in veterinary practice, and may still not be done in some clinics because:
1. Running controls increases costs.
2. Manufacturers may lead vets to believe they don't need to do QC.
3. Practitioner may not know how to interpret QC results.
QA/ QC- microscopes
You need lens cleaner, Windex, alcohol, xylene, lens paper, plastic cover, and routine cleaning. Maintenance by qualified microscope repair people.
QA/ QC- centrifuges
Make sure the timer keeps time, tachometer's correct (there's a device that can check the rpms), samples are being centrifuged for the correct time/ speed (too fast and too long can rupture cells and destroy morphology- controls are run on hematocrit centrifuges for different lengths of time to determine which time gives the correct value), and that it's balanced. Brushes may need to be changed.
QA/ QC- refractometers
You need to keep the surface clean, calibrate it with distilled H2O to give it a zero reading.
QA/ QC- analyzers
Before daily use: Clean surfaces including bar code reader and optical sensor. It has an initial warm- up period. Check the optics of the internal spectophotometer (Reflotron). Do a temperature check (even refrigerators should be monitored).
Daily, weekly, monthly maintenance: According to manual. Cleaning or replacing air filter, replacing lamps, inspecting fuses, and flushing tubing, cuvettes, and aperatures with bleach solution.
Pooled freeze- dried sera, usually from human blood, must be re-hydrated to use. Is screened for infectious disease causing organisms like hepatitis and HIV. Ran on your instrument to asses the instrument and your own technique. If values are within normal range, you assume your unknown value is correct. Frequency of testing depends on the machine. May have low, normal, and high control sera to test the whole range of the instrument. If it's out of range, reconstitute another bottle of control, check expiration date, then start looking for problem (can also try new box of slides or reagent).
"assayed" control sera
Has been tested a statistically correct number of times on the type of instrument you are using to develop a range of values for each of the blood chemistries that can be analyzed on that instrument for each species.
charting control values
Trends: A lamp going out can cause the values to slowly start dropping as can a reagent that's deteriorating. All values may be running below average but still in range, that could be a pipettor malfunction.
Shifts: Sudden changes. Can happen with a new reagent being used, new component that's been added to the instrument, or human error.
Normal: Should see values both above and below average.
*You can call the manufacturer to see if the control values are running like they should be.
Some instruments require calibration prior to use and periodically thereafter or when new lot numbers of reagents are used (calibrators contain known amounts of the constituents and they're tested on the instrument- they are NOT controls).
May also refer to the electronics. VetTest has an autocalibration that compensates for lamp intensity variation (corrects for minor changes). Autocal is also run when a new lamp is put in.
Accuracy: Refers to how closely your results agree with the true value.
Precision: Refers to the reproducibility of the results (repeatability).
Reliability: Refers to the ability of a method to be both accurate and precise.
1. To be useful, abnormal test values must have a high degree of association with the disease condition.
2. Test values that fall within the reference interval are considered negative for a specified disease condition. If the disease is absent, the value is a true negative. If the disease is present, the value is a false negative.
3. Test values that fall outside the reference interval are considered positive for a specified disease condition. If the disease is present, the value is a true positive. If the disease is absent, the value is a false positive.
The ability of a test to identify diseased subjects. It's the frequency with which a test identifies a positive or abnormal test result when the disease is present (how well a test can identify a positive/ abnormal result).
Screening tests need a high degree of sensitivity because false negative results are more unacceptable than false positives).
The ability of a test to identify patients that don't have a particular disease. It's the frequency of a negative or normal test result when a disease is absent (how well a test can identify a negative result).
When an accurate diagnosis is absolutely critical, a highly specific test is required because false positives are unacceptable.
Clerical: Labeling, calculations, transcription.
Systematic: Cause the same error repeatedly (pipette set wrong, delivers too much over and over).
Random: Cause variable errors (pipette is starting to malfunction, gets stuck sometimes and delivers too little).
Sample Quality: Hemolysis, lipemia, age, storage conditions, coagulation, type of antigoagulant used (EDTA for calcium tests, sodium fluoride to preserve glucose), wrong type of sample (serum vs plasma).
Other: Reconstitution errors, storage, outdates, instrument problems with optics, temperatures, timing, etc.
Also called normal values. A set of values for the blood chemistries (or any lab test) from a group of clinically healthy animals as established on a particular instrument. Other parameters, in addition to good health, may be age, sex, breed, environment, or geographic locations.
Determination of reference values: At least 30 animals that fit a stated criteria are used. Mean and SD (Standard Deviation) are calculated. Lower and upper limits of the range are calculated as the mean + and - 2 SDs. Values from 95% of the animals will fall within this range.
Techs can't calibrate the instrument. There's a software disk that comes with each new lot of reagents. Inserted into the back of the machine, this disk contains the calibration info the instrument needs to determine patient values. Idexx recommends that controls be run monthly to verify the VetTest is functioning properly. Running controls verifies the optics and the integrity of the slides. Controls are also run when the analyzer is first installed, it's been bumped or moved, fluid has been spilled on it, or if you think the results are incorrect.
VetTest Chemistry Analyzer
A blood testing instrument that analyzes up to 12 biochemical tests at once. Uses a single sample of serum (or plasma for some tests). Takes about 6 mins to analyze all 12 slides (tests). It's a dry chemistry analyzer- doesn't use liquid reagents.
principle of VetTest
10 micrometers of serum are pipetted onto each slide in succession by the instrument. The serum spreads over the top layer of the slide film and is absorbed. As the serum filters through the other layers, biochemical reactions take place within the film producing progressive color changes. The optical system of the instrument measures the colors and their intensities (it uses reflectometry- has 3 reflectometers operating at 6 wavelengths to perform both endpoint and rate measurements, and the reflective density of each slide- which is a function of the concentration of the analyte- is measured up to 18 times). The system converts the measurements into values, which are displayed on the analyzer screen and printout. The system's software disk contains all calibration data for all lots of slides in use.
All slides can be stored in the freezer. Before use, slides must be brought to room temp (about 15 mins). If not used, unopened slides can be put back in the freezer (can be cycled 5 times- label each time not used). Once opened, slides need to be used within 15 mins.
21 different chemistry tests can be done. They can be purchased seperately or as panels of tests (general health profile or pre-anesthetic panel).
VetTest basic system operation
The analyzer walks you through a series of prompts (short audio "beeps" at each one) to guide you through preparing the pipettor, introducing the sample, and initiating analysis. Sample and slides must be at room temp. The analyzer first requests species info and patient ID. Then you pipette serum according to screen instructions. Analysis starts automatically after pipetting- takes 5-6 mins. 3 beeps signal the completion of analysis. Slides are ejected into used slide drawer. Some serum samples may have to be diluted if analyte concentration is beyond the range capability of the instrument (physiologic saline is used as the diluent, no greater than 1:10).
Best specimen collection time is before treatment, fluid administration, or eating. Minimize stress while drawing blood to avoid affecting test results.
Use appropriate containers (unexpired blood tubes), label and store samples properly before testing.
Remove needle before transferring blood to a tube to minimize hemolysis.
Slow draws increase the chance of clotting.
Gently mix blood immediately if in an EDTA tube or other anti-coagulant.
Fill tube full (1/2 tube is suggested minimum).
Keep in mind how urine was collected and how collection methods may affect results.
Try to collect a midstream catch to avoid excess debris, and use sterile technique for cysto. Suggested minimum amount of urine for urinalysis is 7-10 mls. If not tested within 30 mins, refrigerate. Return to room temp before testing.
Use fresh samples. Place in sealed container, refrigerate until testing is done. Choose sample from mucoid, bloody areas of stool.
Thoracentesis: Pneumothorax, pleural effusion. Collect aspirate in EDTA tube for cell counts and total protein, clot tube for chemistries and culture transport media for culture and sensitivity.
Abdominocentesis: (Uroabdomen, peritonitis, ascites from cardiac or hepatic causes). Collect aspirate in EDTA tube for cell counts, total protein, PCV, and cytology. Clot tube for creatinine, potassium, bilirubin, lactate. Culture transport material.
Peritoneal Lavage: (Infusion of fluid in peritoneal cavity and retrieval of fluid for analysis). Collect fluid in EDTA and clot tubes, culture transport media.
Transtracheal Wash and Aspiration: (To evaluate lower respiratory disease). Looking for bacteria, fungi, parasite eggs/ larvae, neoplastic cells, or presence of inflammation. Samples submitted for aerobic and anaerobic cultures, use appropriate transport media. If submitting sample in the syringe, seal needle with a rubber stopper, refrigerate, and culture within 12 hours. Make cytology smears from both the supernatant and sediment after centrifugation. Be sure to make monolayer smears and air dry, pack in protective container for shipment. For in clinic cytology exam, use Romanovsky's of Giema-type stains.
Aspiration of fluid from a joint. A single drop of synovial fluid is sufficient for gross and histologic appearance. Normal fluid is colorless, clear and viscous, and small amount (<0.3 mls). Cell counts are performed or estimated, differential cell count also performed. Another drop is used for bacterial culture (aerobic, anaerobic, and mycoplasma). If submitting to a reference lab, place synovial fluid in an EDTA tube (decant excess anticoagulant from tube before adding the small amount of fluid to minimize diluting effect).
bone marrow aspiration
Need clean glass slides and EDTA tube. Smears are made immediately with the excess sample put into an EDTA tube- helpful to have 2 people do these 2 tasks at the same time to avoid coagulation. Place a drop of NMB on 1 smear, examine under microscope to determine if sample is adequate or if another sample needs to be taken. CBC with reticulocyte count on peripheral blood is also done to obtain both cell populations (marrow and peripheral).
common chemicals in vet clinics
Cleaning and disinfecting agents.
Insecticides and pesticides.
Drugs and medications.
Radiology processing fluids.
"right to know"
OSHA's law that requires you to be informed of all chemicals you may use or be exposed to. The law also requires you to wear all safety equipment that's prescribed by the manufacturer and the employer when using hazardous chemicals.
Material Safety Data Sheets. Give precautions, instructions, advice for handling, clean up of spills, disposal, and chemical compositions. Clinic is required to keep an MSDS library for all chemicals used.
hazard warning labels
Have to be on secondary containers.
Formaldehyde is a suspected human carcinogen. Use in ventilated area, wear gloves and goggles, obtain formalin in small, prefilled containers for tissue samples.
Transmission by contact with broken skin, ingestion, contact with eyes and mucus membranes, accidental inoculation by a needle, or inhalation. Rabies immunization is available. Important zoonotic diseases: Rabies, bacterial infections (Salmonella, Pasteurella, E. coli, Pseudomonas, Borrelia burgdorferi), ringworm caused by Microsporum canis, Trichophyton mentagrophytes, infection with internal parasites, infestation with external parasites, and protozoal infections.
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