Equations

Question 1

Sensitivity

Answer 1

Sensitivity = TP / (TP + FN)

Question 2

Specificity

Answer 2

Specificity = TN / (TN + FP)

Question 3

Positive predictive value

Answer 3

PPV = TP / (TP + FP)

Question 4

Negative predictive value

Answer 4

NPV = TN / (TN + FN)

Question 5

Odds ratio (for case-control studies)

Answer 5

Odds ratio = (a/c)/(b/d) = ad / bc

Question 6

Relative risk

Answer 6

Relative risk = [a / (a + b)] / [c / (c + d)]

Question 7

Attributable risk

Answer 7

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

Question 8

Number needed to treat

Answer 8

1 / absolute risk reduction

Question 9

Number needed to harm

Answer 9

1 / attributable risk

Question 10

Body mass index

Answer 10

BMI = weight in kg / (height in meters)^2

Question 11

Hardy-Weinberg equilibrium

Answer 11

p^2 + 2pq + q^2

p + q = 1

Question 12

Volume of distribution (Vd)

Answer 12

Vd = amount of drug in body / plasma drug concentration

Question 13

Half-life

Answer 13

t1/2 = 0.7 x Vd / CL

Question 14

Drug clearance (CL)

Answer 14

CL = rate of elimination of drug / plasma drug concentration
CL = Vd x Ke (elimination constant)

Question 15

Loading dose

Answer 15

LD = Cp (plasma concentration) x (Vd / bioavailability)

Question 16

Maintenance dose

Answer 16

MD = Cp (plasma concentration) x CL

Question 17

Cardiac output

Answer 17

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

Question 18

Mean arterial pressure

Answer 18

MAP = CO x TPR
MAP = 2/3 diastolic + 1/3 systolic

Question 19

Stroke volume

Answer 19

SV = CO / HR
SV = EDV - ESV

Question 20

Ejection fraction

Answer 20

EF = SV / EDV
EF = (EDV - ESV) / EDV

Question 21

Resistance

Answer 21

Resistance = [driving pressure (change in P)] / flow (Q)
Resistance = [8n (viscosity) x length] / (pi x r^4)

Question 22

Net filtration pressure

Answer 22

Pnet = [(Pc - Pi) - (pi c - pi i)]
Jv = net fluid flow = Kf x Pnet

Question 23

Renal clearance

Answer 23

C = (U x V) / P

Question 24

Glomerular filtration rate

Answer 24

GFR = Uinulin x V/Pinulin = Cinulin
GFR = Kf [Pgc - Pbs) - (pi gc - pi bs)]

Question 25

Effective renal plasma flow

Answer 25

ERPF = Upah x (V / Ppah) = Cpah

Question 26

Renal blood flow

Answer 26

RBF = RPF / (1 - Hct)

Question 27

Filtration fraction

Answer 27

FF = GFR / RPF

Question 28

Henderson-Hasselbalch equation (for extracellular pH)

Answer 28

pH = 6.1 + log ([HCO3] / 0.03 Pco2)

Question 29

Physiologic dead space

Answer 29

Vd = Vt x [(PaCO2 - PeCO2) / PaCO2]

Question 30

Pulmonary vascular resistance

Answer 30

PVR = (Ppulm artery - Pleft atrium) / CO

Question 31

Alveolar gas equation

Answer 31

PAO2 = PIO2 - (PaCO2 / R)