Clinical Chemistry Part 1.1 Flashcards
Basic Principles to Laboratory Statistics
What is the prefix and symbol for the following?
a. 10^1
b. 10^-1
c. 10^-2
d. 10^-3
a. deka (da)
b. deci (d)
c. centi (c)
d. milli (m)
What is the prefix and symbol for the following?
a. 10^-6
b. 10^-9
c. 10^-12
d. 10^-15
a. micro (u)
b. nano (n)
c. Pico (P)
d. femto (f)
What are the commonly used prefixes in expressing analyte concentrations?
milli, micro, nano, and pico
What is the prefix used in expressing the Mean Corpuscular Volume (MCV)?
femto
Convert. 1.0 L to uL.
1,000,000 uL
Note:
- L is a basic unit (including meter and gram), so the factor is 10^0.
- u has a factor of 10^6.
- To convert larger unit to smaller unit, get the difference of the exponents and move decimal to the right.
- If smaller unit to larger unit, move decimal to the left.
Convert 5mL to uL.
5,000 uL
Convert 5.3 mL to dL.
0.053 dL
Convert 200 uL to mL.
0.2 mL
Convert 0.00005 ng to pg.
0.5 pg
2500 pmol to mmol.
0.000002500 or 0.0000025
0.4 um to m
0.0000004
moles per L of solution
Molarity
moles per kg solvent
Molality
equivalent weights per L of solution
Normality
the amount of solute per 100 total units of solution
% w/v
volume of sample divided by total volume of solution; expression of relative concentration
Dilution
amount of something relative to
another; expressed as part per part or part per whole
Ratio
What is the conversion factor for the following analyte?
mg/dL to mmol/L
a. Glucose
b. Urea
c. BUN
d. Uric acid
a. 0.0555
b. 0.167
c. 0.357
d. 0.0595
What is the conversion factor for the following analyte?
mg/dL to mmol/L
a. Cholesterol, HDL-C, LDL-C
b. Triglyceride
c. Calcium
d. Magnesium
a. 0.026
b. 0.0113
c. 0.25
d. 0.417
What is the conversion factor for the following analyte?
mg/dL to mmol/L
a. Phosphorus
b. Lactate
a. 0.323
b. 0.111
What is the conversion factor for the following analyte?
mEq/dL to mmol/L
a. Ca2+, Mg2+
b. Na+, K+, Cl-, HCO3-
a. 0.5
b. 1
What is the conversion factor for the following analyte?
mg/dL to umol/L
a. Creatinine
b. Bilirubin
a. 88.4
b. 17.1
What is the conversion factor for the following analyte?
ug/dL to umol/L
a. Ammonia
b. Iron
c. Cortisol
a. 0.588
b. 0.179
c. 0.0276
What is the conversion factor for the following analyte?
ug/dL to nmol/L
a. T4
b. T3
c. Folic Acid
a. 12.9
b. 0.0154
c. 2.27
What is the conversion factor for the following analyte?
pg/dL to pmol/L
a. Vitamin B12
a. 0.738
What is the conversion factor for Proteins (TPAG), g/dL to g/L?
10
known as the nitrogen content of urea
BUN
average or arithmetic mean
Mean
midpoint of a data set after the values have been RANK-ORDERED
Median
midpoint of a data set after the values have been RANK-ORDERED
Median
most frequently occurring value in a data set
Mode
What are the measures of central tendency?
mean, median, mode
distribution of data points around the mean
Standard Deviation (s)
Summation of the squares of the differences between the mean and its
observation divided by the total number of observations minus one
degree of freedom.
Variance (s^2)
best indicator of precision; expressed in percent
Coefficient of Variation (CV)
difference between the highest and lowest values in a data set; most unreliable when outliers are present
Range
What are the measures of distribution/spread/variability?
standard deviation, variance, coefficient of variation, range
Values that deviate greatly from the mean
Outliers
What is the relation between CV and precision?
They are inversely related, in which high precision equates to low CV. The lower the CV, the higher the precision.
What is the empirical rule in Gaussian or Normal Distribution?
68-95-99.7
Note:
- 68% of the values fall in +/- 1 SD
- 95% of the values fall in +/- 2 SD
- 99.7% of the values fall in +/- 3 SD
When verifying a reference interval, at least _____ study individuals are required; RI is adopted if _____ of the subjects fall outside the range.
20; less than or equal 10%
What do we do if there is no existing reference interval for an analyte or when transference studies fail?
establish a reference interval
In establishing a reference interval at least ______ study individuals are required.
120
→ First step in method evaluation; usually done by running two controls materials twice a day over a 10-day period.
→ Also known as 2x2x10
Precision Study
→ Involves spiking a sample with a known amount of an analyte and determining how much of it can be detected by the method in presence of another compound in the matrix.
Recovery Study
Compares the means of two groups of data or the accuracy of the two methods.
T-test
Compares the standard deviation of two groups of data or the precision of two methods.
F-test
→ Used to compare two methods using the best fit line through the data points.
→ X = independent variable/ reference method
→ Y = dependent variable/ new method
Linear regression
→ Ability of a method to detect the smallest concentration of an analyte.
→ Not prone to false negative; desired in screening test
Analytical Sensitivity
→ Ability of a method to detect only the analyte of interest.
→ Not prone to false positive; desired in confirmatory test
Analytical specificity
Ability to detect the presence of a given disease or condition.
Diagnostic Sensitivity
Ability to detect the absence of a given disease or condition.
Diagnostic Specificity
Probability that a positive result indicates disease or presence of a
disease or condition.
Positive Predictive Value
Probability that a negative result indicates absence of a disease or condition
Negative Predictive Value
PPV, NPV, Specificity, Sensitivity Problems (see link)
https://drive.google.com/file/d/1-dXEKR8Z3-b8f75xuOjcOFiSv5tHVwj9/view?usp=sharing
It is important to know and understand the clinical implications of the sensitivity and
specificity of diagnostic tests. The Prostate Specific Antigen (PSA) is one example. This
test has a sensitivity of 86% but a specificity of only 33%. What is the implication of
having these results?
https://drive.google.com/file/d/12JIQ10I3s4K1KmY89N806ZmyOszVHmP5/view?usp=sharing
What is the implication of having an 80% Positive Predictive Value and a 70% Negative
Predictive Value?
https://drive.google.com/file/d/12JIQ10I3s4K1KmY89N806ZmyOszVHmP5/view?usp=sharing