biochem exam 2

What is used to verify the acceptability of new methods prior to reporting patient results?

Method evaluation

What is the first step of method evaluation?

Determine imprecision and inaccuracy

What is the foundation for monitoring performance (known as QC)?

Descriptive statistics

What are the three measures of center?

Mean, median, mode

What is the most commonly used measure of center and often called the average?

Mean

What is the middle point and is often used with skewed data so that outliers do not significantly affect the calculation?

Median

What is the measure of center that is rarely used and is the most frequently occurring value in a data set?

Mode

What is the term for how data is distributed?

Spread

What is the term for distribution of a data set?

Shape

What is the difference between test and reference method results?

Error

What is the term for when the mean, median, and mode are identical and distribution is symmetrical?

Gaussian or bell curve

What is the total area under a Gaussian distribution?

1\.0 or 100%

What percent falls within 1 SD?

68\.3%

What percent falls within 2 SD?-

95\.4%

What percent falls within 3 SD?

99\.7%

What involves measuring patient specimens by both existing reference and new test methods?

Comparison of methods experiment

What type of analysis provides objective measures of location and dispersion of line

Linear regression

Which error is present in all measurements and can be either positive or negative?

Random error

What error can result from factors including instrument, operator, reagent, or environmental variation?

Random error

Which error influences observations consistently in one direction?

Systematic error

What type of systematic error is in the sample direction and magnitude; magnitude of change is constant and not dependent on the amount of analyte?

Constant error

What type of systematic error is where the magnitude changes as a percent of the analyte present, error dependent on analyte concentration?

Proportional error

What is a random error plus systematic error?

Total error

What are the descriptive statistics of groups of paired observations?

1. Comparison of methods experiment
2. Linear regression
3. Types of errors

What is used to draw conclusions regarding means or standard deviations of two sets of data?

Inferential statistics

What are the two primary government agencies that influence laboratory testing methods?

What are the two primary government agencies that influence laboratory testing methods?

CLIA Regulations for method validation for Nonwaived FDA-Approved tests

1. Demonstrate test performance comparble to that established by manufacturer
a. Accuracy
b. Precision
c. Reportable range
2. Verify reference values appropriate for patient population

CLIA Regulations for method validation for Nonwaived FDA-Approved tests modified or developed by laboratory

1\. Determine \n a. Accuracy \n b. Precision \n c. Analytic sensitivity \n d. Analytic specificity \n e. Reportable range of test results \n f. Reference ranges \n g. Other performance characteristics \n h. Calibration and control procedures

What is new methods selected to reduce costs, improve quality, satisfy clients, or improve efficiency called?

Method selection

What is the dispersion of repeated measurements about the mean due to analytic error?

Imprecision

What is the term for how close the measured value is to the true value due to systematic error?

Inaccuracy

Measurement imprecision

1. Estimates random errors associated with test methods
2. Detects any problems affecting its reproducibility
3. Should be performed over a 10 to 20 day period

Imprecision or Inaccuracy

Imprecision

Imprecision or Inaccuracy

Inaccuracy

How is precision best measured?

Coefficient of Variation

What are the estimations of inaccuracy?

1. Recovery studies
2. Interference studies
3. Comparison of method studies

What shows whether a method is able to accurately measure an analyte?

Recovery studies

What determines if specific compounds affect accurate determination of analyte concentrations?

\n

Interference studies

What examines patient samples by method being evaluated (test) with a reference method?

Comparison of Methods studies

What are methodologies used in past to estimate medically allowable error?

Allowable Analytic Error

Who published error limits allowable by federally mandated proficiency testing

CLIA

What is the ability of a method to detect small quantities or small changes in concentration of an analyte?

Analytic sensitivity

what is the ability of a method to detect only the analyte it is designed to determine?

Analytic specificity

What is the proportion of people with disease who test positive?

Clinical sensitivity

What is the ability of a test to correctly identify the absence of a given disease or condition?

Diagnostic specificity

What is the ability of a test to detect a given disease or condition?

Diagnostic sensitivity

What is positive predictive value?

chance of an individual having a given disease if the test is abnormal

What is negative predictive value?

Chance an individual does not have a disease if the test is within the reference interval

What is the formula for specificity?

TN/(TN + FP)

What is the formula for positive predictive value?

TP/(TP+FP)

what is the formula for negative predictive value?

TN/(FN + TN)

Why type of curves are generated by plotting the true-positive rate against the false-positive rate?

ROC curves

What involves detecting and preventing errors that can eliminate potential negative patient impact events?

Quality improvement and quality assurance

What did the the Six Sigma business management strategy do?

Identified and eliminated causes of defects and errors

What did the principles of the Lean manufacturing strategy do?

Principles work to eliminate the waste

What achieves new levels of performance not otherwise realized through quality control?

Quality improvement

What are the factors for quality improvement?

Culture: relentless pursuit of improvement toward excellence \n Methodology: waste elimination and variation reduction \n Metric: Lean Six Sigma

What does the Lean mean in Lean Six Sigma?

Eliminate non-value-adding steps and reduce cycle time

What is the difference in standard deviation and coefficient of variation?

CV normalizes the SD with respect to the mean; \n SD is more proportional to the mean & therefore is more affected by it

What involves systematic monitoring of analytic processes to detect analytic errors that occur during analysis and ultimately prevents reporting of incorrect patient test results?

Quality control

What graphically represents observed values of a control material over time in context of upper and lower limit controls?

QC charts

How are controlled limits expressed?

Mean +/- the SD

What are the three stage process for operation of a quality control system?

1. Establishing allowable statistical limits of variation
2. Using limits as criteria for evaluating quality control data
3. Taking action to remedy errors when indicated

What is a method used to validate a particular measurement process and required by CAP, CLIA, JCAHO to maintain lab accreditation?

proficiency testing

What are the 4 strict requirements for proficiency testing?

1. Lab must incorporate proficiency testing into its routine workflow as much as possible
2. Test values/samples must not be shared with other labs at any time during testing cycle
3. Proficiency samples are tested by bench technical staff who normally do patient testing
4. Testing should be completed within usual time

What variables must be controlled and standardized to generate a valid reference interval?

pre-analytic and analytic

Parameters used to determine how good a given test is at detecting and predicting presence of disease is important for?

Diagnostic deficiency

What does the Six Sigma mean in Lean Six Sigma?

Reduce variation and error

What is the proportion without disease who test negative?

Specificity

What is the formula for sensitivity?

TP/(TP + FN)

What does DMAIC stand for in six sigma?

Define, Measure, Analyze, Improve, Control

What part of DMAIC aids to end users of services or products, their needs and expectations, project boundaries, process?

Define

Which part of DMAIC collects data, determines defects, and assesses satisfaction?

Measure

Which part of DMAIC examines data to identify root causes of error?

Analyze

Which part of DMAIC fixes problems and prevent future ones with creative solutions?

Improve

Which part of of DMAIC aids in continuous monitoring of new plans?

Control

What describes practices, procedures, and resources needed by the laboratory to ensure the quality of a testing process?

Quality control plan (QCP)

Who assigned technical committee 212 the task of creating global standards for quality and competence in medical laboratories?

International Organization for Standards (ISO)

The basic requirements for ISO 15189 certification includes what

A well-documented procedure analysis by the laboratories and a training manual provided by the laboratories

What is the formula for Sigma?

Sigma = (total allowable error - bias)/CV

What measures light intensity without consideration of wavelength?

Photometric instruments

Beer's Law

The concentration of a substance is directly proportional to the amount of light absorbed or inversely proportional to the logarithm of the transmitted light

Absorbance formula

A = 2-log%T

A = abc what does each stand for?

A: Absorbance \n a: Molar absorptivity \n b: Path length in cm. \n c: Concentration of analyte

What are the components of a spectrophotometer?

Light source \n Monochromators \n Sample cell \n Photodetectors

What is the most common spectrophotometer lamp for vis?

Tungsten

What is the most common spectrophotometer lamp for UV?

Deuterium or Mercury Arc

What do the monochromators do?

Isolates individual wave lengths (filter/prism)

What do the photodetectors do?

Convert transmitted energy to electrical energy that can be read by the detector

What is the sample cell?

Usually a flat surface

What does the Atomic Absorption Spectrophotometer do?

Measures concentration by detecting absorption of electromagnetic radiation by atoms rather than by molecules

What is routinely used to measure concentration of trace metals that are not easily excited?

Atomic Absorption Spectrophotometer (AA Spectrophotmeter)

What is the usual light source for AA Spectrophotometers and is specific for the analyte of interest?

Hollow cathode lamp

What measures light emitted by excited atoms?

Flame photometry

What is part of chemical energy generated produces excited intermediates that decay to a ground state with emission of photons?

Chemiluminescence

How is chemiluminescence different from fluorescence

No excitation radiation or monochromators required

What are advantages to fluormetry?

Greater specificity & sensitivity

What are disadvantages to fluormetry?

Very sensitive to environmental changes

What measures concentration of particulate matter in sample in a straight line?

Turbidimetry

What measures concentration of light scatter in sample at different angles?

Nephelometry