What is the definition of Positive Predictive Value (PV)?
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True positives / (True positives + False positives)
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What is the definition of Positive Predictive Value (PV)?
True positives / (True positives + False positives)
What is the definition of Negative Predictive Value (PV)?
True negatives / (True negatives + False negatives)
What is the definition of control?
Specimen is similar to patient’s blood, known concentration of constituent.
What is the definition of precision in clinical quality assessment?
How close the test results are to one another when repeated analyses of the same material are performed.
What are some common issues related to laboratory results?
Unavailable or delayed laboratory results, long turnaround time, incomplete laboratory results, wrong transcription of patient data and laboratory results, missing laboratory results, laboratory results submitted to the wrong physician.
What is the first step in method evaluation?
The precision study.
What is the Youden/Twin Plot used for?
To compare results obtained on a high and low control serum from different laboratories.
What is the definition of accuracy?
Describes how close a test result is to the true value.
What is a Gaussian curve?
A normal bell-shaped curve that represents the distribution of values around the mean in a statistically valid series.
What does a Lean Clinical Laboratory aim to achieve?
Utilizes fewer resources, reduces costs, enhances productivity, promotes staff morale, and improves the quality of patient care.
What is the SD?
The square root of the variance of the values in any one observation or in a series of test results.
What does a point falling from the center but on the 45° line in a Youden/Twin Plot suggest?
A proportional error.
What are analytical errors attributed to?
Operator or instrument error.
When do post-analytical errors occur?
After the analysis is complete but within the confines of the laboratory.
What is a false positive in the context of laboratory testing?
A subject who has a positive test result but does not have the disease.
What are the basic statistical concepts that enable a learner to measure quality?
Accuracy, precision, specificity, and sensitivity.
What does a negative predictive value (PV) indicate?
The number of patients with a normal test result who do not have the disease, compared with all patients with a normal (negative) result.
What is the definition of calibration?
Comparison of an instrument measure or reading to a known physical constant.
What does the precision study estimate?
Random error.
What is the definition of variance in clinical quality assessment?
A general term that describes the factors or fluctuations that affect the measurement of the substance in question.
What percentage of values fall within the third standard deviation (±3 SD) in a normal population?
99.7%
What is the definition of accuracy in clinical quality assessment?
How close a test result is to the true value.
What is the definition of calibration?
The comparison of an instrument measure or reading to a known physical constant.
What is the definition of standards in clinical quality assessment?
Highly purified substances of a known composition.
What is the purpose of using QC specimens in laboratory testing?
To indicate the overall reliability (both accuracy and precision) of the results reported by the laboratory.
How is imprecision or random error studied?
By running 2 control solutions twice a day over a 10-to-20-day period.
What is the most accurate measure of performance affecting laboratory values?
Total imprecision analysis.
What should a laboratory procedure manual include?
A comprehensive listing of approved policies, acceptable practices, and precautions.
What should a written record of QC activities include?
Details of deviation from usual results, problems, failures in functioning or analytical procedure, and corrective actions taken.
What is a common method used in CUSUM?
V mask.
What is the mode?
The value most frequently occurring in a list of numbers.
What is standard deviation (SD)?
A measure of the spread, or variability, in a data set.
What does it indicate when quality control is outside of acceptable limits?
A potential issue with the accuracy or precision of the test results.
What is a defect in Six Sigma?
Anything that does not meet customer requirements.
What is the primary goal of a Lean System?
Reducing waste (nonvalued activities).
What are the indicators of analytic performance?
Internal QC, proficiency testing, accreditation, quality assurance monitoring, and laboratory utilization.
What is a Shewhart Levey-Jennings Chart?
A graphic representation of the acceptable limits of variation in the results of an analytic method.
What type of problems does CUSUM identify?
Consistent bias problems.
What is the definition of specificity?
Cases without a specific disease or condition produce a negative result.
What type of error is associated with accuracy in testing?
Analytical error.
What does Six Sigma aim to improve in the clinical laboratory?
Process by eliminating variations or errors, improved performance, improved quality, improved bottom line, improved customer satisfaction, and improved employee satisfaction.
What is the definition of a control specimen?
A material or solution with a known concentration of the analyte being measured in the testing procedure.
What does quality control (QC) consist of?
Procedures used to detect errors from test system failure, adverse environmental conditions, and variance in operator performance.
What is the definition of quality control?
A process that monitors the accuracy and reproducibility of results through the use of control specimens.
What is the definition of precision?
How close results are to one another.
What are Westgard Rules used for?
To analyze data in control charts based on statistical methods and detect both random and systematic errors.
What is the definition of standards?
Highly purified substance of a known composition.
What percentage of values fall within the second standard deviation (±2 SD) in a normal population?
95%
What type of error occurs when a specimen is collected in the wrong tube?
Preanalytical error.
What type of error is associated with critical value reporting?
Postanalytical error.
What is clerical error?
Error with the highest frequency due to the use of handwritten labels and request forms.
What does the incidence of a disease refer to?
The number of subjects found to have the disease within a defined period in a population of 100,000.
How are defects generally measured in Six Sigma?
Per million opportunities (DPMO).
What are the majority of laboratory errors related to?
Preanalytical or postanalytical phases of testing.
What does the Cumulative Sum Graph (CUSUM) calculate?
The difference between QC results and the target means.
What is the median?
The middle value of a body of data when arranged in order of increasing magnitude.
What is the earliest indication of systematic errors in CUSUM?
When the slope exceeds 45° or a decision (±2.7 SD) is exceeded.
What is the definition of sensitivity?
Cases with specific disease or condition produce a positive result.
What type of error is associated with patient identification?
Preanalytical error.
What is the main goal of Six Sigma?
To reduce the number of defects to near zero.
What is proportional/slope/percent error?
Error that results in greater deviation from the target value due to higher sample concentration.
What is standard deviation (SD) used to express in laboratory tests?
Precision or reproducibility of a test.
What does the prevalence of a disease refer to?
The proportion of a population who has the disease.
What is the mean?
The mathematical average calculated by taking the sum of the values and dividing by the number of values in the list.
What do QC activities include?
Monitoring the performance of laboratory instruments, reagents, other testing products, and equipment.
What percentage of values fall within the first standard deviation (±1 SD) in a normal population?
68%
What is a Delta Check?
A patient-based QC technique that compares current results with past results of the same analytes on the same individual.
What does the term 'reference range' mean?
The range of values that includes 95% of the test results for a healthy reference population.
What is random error?
Error present in all measurements due to chance, varying from sample to sample.
What is systematic error?
Error that influences observations consistently in one direction, often related to calibration problems and other consistent issues.
What is a true positive in the context of laboratory testing?
A subject who has a positive test result and also has the disease in question.
What must be done if the value of the QC specimen is not within the predetermined acceptable range?
The values obtained for the unknown specimens are assumed to be incorrect, and the results are not reported until the error is found and corrected.
What do pre-analytical errors refer to?
Inappropriate performances before specimens are measured by analyzers.
What does a point falling from the center but not on the 45° line in a Youden/Twin Plot suggest?
A constant error.
What is an example of an analytical error?
Incorrect sample and reagent volume.
What is the coefficient of variation (CV) used to express in laboratory tests?
Precision or reproducibility of a test.
What is an example of a pre-analytical error?
Wrong or missing patient identification.
What is a confidence interval?
The range expressed using 2 SD on either side of the mean, with 95% of the values falling above and below the mean.
What is the definition of sensitivity in a laboratory test?
The proportion of cases with a specific disease or condition that give a positive test result.
What does a positive predictive value (PV) for a test indicate?
The number of patients with an abnormal test result who have the disease, compared with all patients with an abnormal result.
What does precision refer to in a laboratory procedure?
Repeatability or reproducibility of obtaining the same value in subsequent tests on the same sample.
What is a false negative in the context of laboratory testing?
A subject who has a negative test result but does have the disease.
What is constant error?
A difference between the target value and the assayed value, independent of sample concentration.
What is the definition of specificity in a laboratory test?
The proportion of cases with the absence of the specific disease or condition that give a negative test result.
What does the accuracy of a procedure refer to?
Closeness of the result obtained to the true or actual value.
What is a true negative in the context of laboratory testing?
A subject who has a negative test result and does not have the disease.
