Laboratory Administration Flashcards
Percentages at 1,2,3 SD if Gaussian
1sd=68%
2sd=95.5%
3sd=99.7%
SD=
average distance of a value from the mean
Mode
most frequent value
Coefficient of variation
describes the sd as % of the mean at a particular analyte concentration
CV=
SD/meanx100
Clinical sensitivity
positivity in presence of disease
Sensitivity=
TP/(TP+FN)
Specificity=
TN(TN+FP)
PPV definition
percent of + results that actually indicate dz
PPV=
TP/all+
NPV=
TN/all-
when dz prevalence is low, PPV ___, NPV ____
PPV decreases
NPV increases
Punnett square
x=dz, y = test result,
top left = True positive
bottom right = true negative
Relative risk definition
risk of an outcome “Y” in the presence of condition “X” as compared to the population
RR=
(#with X who develop Y/#with X) / (#in pop with Y/# in pop)
ordinal scale
gives a number with an assigned value (ex. urine protein 1+)
ROC curve
X-axis = 1-specificity (1-false+) Y-axis = sensitivity (true+)
ROC curve provides
view of whole spectrum of sensitivities and specificities at different cut off values
Most accurate point on ROC curve
closest to upper left corner
Wesgard rules
1:3s = 1 value 3sd above mean
2:2s = 2 in row 2sd on same side
R:4s = two values >4sd from each other
4:1s = 4 in a row 1sd on same side
10:mean = 10 on same side of mean
Westguard rules addressing drifts and shifts
(systematic errors)
2: 2s
4: 1s
10: mean
agency approving proficiency testing
Dept of Health and Human Services
Satisfactory proficiency testing
acceptable results in >4/5
3x/yr x 5 samples
random variability increases with
increasing [analyte]
analytical sensitivity
lowest analyte concentration detectable
analytical sensitivity calculation
mean + 3sd (of lots of runs with no analyte)
interferences are responsible for a ____ bias
constant
solvent exclusion effect
indirect ISE
lipemia, paraprotein
when sitting, concentration of ____ goes ___ by __%
proteins, cells, things bound to proteins
up
5-15%
order of collection
Culture Red Blue Green Purple Gray
Anion gap
Na- (Cl+HCO3)
osmolal gap
measured - (2Na + Glu/18 + BUN/2.8)
Friedewald equation
LDL=Tchol-HDL-TG/5
FENA=
(Urine Na x Plasma creat)/(Urine creat x Plasma Na)
Correction of anion gap for hypoalbuminemia
+2.5(4-albumin)
