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Flashcards in Equations Deck (26):
1

Sensitivity

sensitivity = TP/(TP + FN) = 1 - FN rate

(TP= true positive; FN = false negative)

2

Specificity

specificity = TN/(TN + FP) = 1 - FP rate

3

Positive Predictive Value

PPV = TP/(TP+FP)

4

Negative Predictive Value

NPV=TN/(TN+FN)

5

Relative Risk

R=[a/(a+b)]/[c/(c+d)]

6

Attributable Risk

AR=[a/(a+b)] - [c/(c+d)]

*AR - difference in risk between exposed and unexposed groups, or the proportion of disease occurrences that are attributable to the exposure (ie smoking causes 1/3rd of cases of pneumonia)

7

Number needed to treat =

1/absolute risk reduction

*Absolute risk reduction - reduction in risk associated with a treatment compared to a placebo

8

Number needed to harm =

1/attributable risk

9

Hardy-Weinberg equilibrium =

p^2 + 2pq + q^2 = 1
p+q = 1

*p^2 - frequency of homozygosity for allele p
*q^2 - frequence of homozygosity for allele q
*2pq - frequency of heterozygosity (carrier frequency)

10

Henderson-Hasselbach equation =

pH = pKa + log [HCO3-]/(0.3XPCO2)

11

Volume of distribution

Vd= (amount of drug in body)/(plasma drug concentration)

12

Clearance

CL = rate of elimination of drug/plasma drug concentration

13

Half-Life

t1/2 = (0.7XVd)/CL

14

Loading dose

LD = Cp X (Vd/F)

*Cp=target plasma concentration
*F=Bioavailability = fraction of administered drug that reaches circulation (if IV, F=100%; if oral, F=% that survives first pass in liver or gut)

15

Maintenance dose

MD = Cp X (CL/F)

16

Cardiac output

CO = rate of O2 consumption/ (arterial O2 content - venous O2 content)

-AND-

CO = stroke volume X heart rate

17

Mean Arterial Pressure

MAP = CO X total peripheral resistance

-AND-

MAP = 1/3 systolic + 2/3 diastolic

18

`Stroke Volume

SV = end diastolic volume - end systolic volume

19

Ejection Fraction

EF = (Stroke volume/End diastolic volume) X 100

20

Resistance

R = driving pressure / flow

= (8 X viscosity X length) / (pi X r^4)

21

Net filtration pressure

Pnet = [(Pc-Pi) - (rc - ri)]

*Pc=capillary pressure --> pushes fluid out of capillary
*Pi=interstitial fluid pressure --> pushes fluid into capillary
*rc= (r should be sigma) plasma colloid osmotic pressure --> pushes fluid into capillary
*ri= interstitial fluid colloid osmotic pressure --> pushes fluid out of capillary

22

Glomerular filtration rate

GFR= Uinulin X (V/Pinulin) = Cinulin

= (urine concentration X urine flow) / Plasma concentration

*Uinulin = urine inulin
*Pinulin = plasma inulin
*Cinulin = clearance of inulin
*V = urine flow rate

-AND-

GFR = Kf [(PGC - PBS) - (rGC - rBS)]

*GC = glomerular capillary
*BS = Bowman's space
*rBS - normally equals 0

*** Normal GFR = 100 mL/min

23

Effective renal plasma flow

ERPF = Upah X (V/Ppah) = Cpah

24

Renal blood flow

RBF = RPF / (1-Hct)

25

Filtration fraction

FF = GFR / RPF

26

physiologic dead space

VD = VT X (PaCO2 - PeCO2)/PaCO2