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22 Cards in this Set
- Front
- Back
Sensitivity |
is the ability of an analytical method to measure the smallest concentration of the analyte of interest. |
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Specificity |
is the ability of an analytical method to measure only the analyte of interest. |
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Accuracy |
the nearness or closeness of the assayed value to the true or target value. |
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Precision or reproducibility |
the ability of an analytical method to giverepeated results on the same sample that agree with one another. |
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Practicability |
the degree by which a method is easilyrepeated. |
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Reliability |
the ability of an analytical method tomaintain accuracy and precision over an extended period of time during which equipment, reagents and personnel may change |
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Diagnostic sensitivity |
is the ability of the test to detect theproportion of individuals with that disease who test positively with the test.- indicates the ability of the test to generatemore true-positive results and few false negative. |
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Diagnostic sensitivity formula |
Sensitivity (%) = 100 x the number of diseased individuals with a positive test ÷ Total number of diseased individuals |
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Diagnostic specificity |
- is the ability of the test to detect theproportion of individuals without the disease who testnegatively for the disease. - it reflects the ability of the method to detect true-negative with very few false-positives |
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Diagnostic specificity formula |
Specificity (%) = 100 x the number of individuals without the disease with a negative test ÷ total number of diseased individuals |
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Intralab (internal QC) |
- it involves the analyses of control samplestogether with the patient specimens. - it detects changes in performancebetween the present operation and the “stable” operation. -detects both random and systematic errors. |
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Interlab (internal QC) |
- it involves proficiency testing programsthat periodically provide samples of unknown concentration of analytes to participating laboratories. - it is important in maintaining long-term accuracy of the analytical methods.- it is also used to determine estimates of the state-of-the-art interlaboratory performance. - difference of >2 in the results indicates that a laboratory is not in agreement with the rest of the laboratories included in the program. |
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Objectives of QC |
1. To check the stability of the machine. 2. To check the quality of reagents. 3. To check technical errors. |
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Characteristics of an Ideal QC Material |
1. Resembles human sample. 2. Inexpensive and stable for long periods. 3. No communicable diseases. 4. No matrix effects/known matrix effects. 5. With known analyte concentrations. 6. Convenient packaging for easy dispensing and storage. |
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5 and 20 |
the different levels of control material must be analyzed between _______ days. |
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mean and standard deviation (SD). |
Control limits are calculated from the ________ and ________ |
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human sample |
Quality control materials should resemble __________ and be available for a minimum concentrations which requires new estimates of the mean and standard deviation. |
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single lot |
Use of a _______ for an extended period allows reliable interpretative criteria to be established which will permit efficient identification of an assay problem. |
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Human control materials |
are preferred but because of limited sources and biohazard considerations, bovine control materials are used. |
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Bovine-based QC material |
is NOT the choice for immunochemistry, dye-binding and certain bilirubin assays. |
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Matrix effects |
are results of improper product manufacturing, use of unpurified human and nonhuman analyte additives and altered protein components. |
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Assayed controls |
are more expensive but can be used as external checks for accuracy.Determination of the mean and SD for the unassayed controls is also advisable because this process improves the performance characteristics of statistical control procedures. |