Equation Review

Question 1

Sensitivity

Answer 1

Sensitivity = TP / (TP + FN)

Question 1

Specificity

Answer 1

Specificity = TN / (TN + FP)

Question 2

Positive predictive value

Answer 2

PPV = TP / (TP + FP)

Question 3

Negative predictive value

Answer 3

NPV = TN / (TN+FN)

Question 4

Odds ratio (for case-control studies)

Answer 4

Odds ratio = a/c | b/d = ad | bc

Question 5

Relative risk

Answer 5

Relative risk = a/(a+b) | c/(c+d)

Question 6

Attributable risk

Answer 6

Attributable risk = a | a+b - c | c+d

Question 7

Number needed to treat

Answer 7

I/absolute risk reduction

Question 8

Number needed to harm

Answer 8

I/atrtributable risk

Question 9

Body mass index

Answer 9

BMI = weight in kg / height in meters squared

Question 10

Hardy-Weinberg equilibrium

Answer 10

p squared + 2pq + q squared = 1

p + q = 1

Question 11

Volume of distribution

Answer 11

Vd = amount of drug in the body / plasma drug concentration

Question 12

Half-life

Answer 12

t half = 0.7 x Vd / CL

Question 13

Drug clearance

Answer 13

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

Question 14

Loading dose

Answer 14

LD = Cp x Vd / F

Question 15

Maintenance dose

Answer 15

MD = Cp x CL / F

Question 16

Cardiac output

Answer 16

CO = rate of O2 consumption / arterial O2 content - venous O2 content
CO = stroke volume x heart rate

Question 17

Mean arterial pressure

Answer 17

MAP = cardiac output x total peripheral resistance
MAP = 2/3 diastolic + 1/3 systolic

Question 18

Stroke volume

Answer 18

SV = CO/HR = EDV-ESV

Question 19

Ejection fraction

Answer 19

EF = SV/EDV = EDV-ESV/EDV

Question 20

Resistance

Answer 20

Resistance = driving pressure (ΔP) / flow (Q) = 8η (viscosity) x length / πr to the fourth

Question 21

Net filtration pressure

Answer 21

Pnet = [(Pc - Pi) - (πc - πi)]
Jv = net fluid flow = (Kf)(Pnet)

Question 22

Renal clearance

Answer 22

Cx = UxV/Px

Question 23

Glomerular filtration rate

Answer 23

GFR = U inulin x V/P inulin = C inulin
GFR = Kf [(Pgc - Pbs) - (πgc - πbs)]

Question 24

Effective renal plasma flow

Answer 24

ERPF = U pah x V / P pah = C pah

Question 25

Renal blood flow

Answer 25

RBF = RPF/1-Hct

Question 26

Filtration fraction

Answer 26

FF = GFR/RPF

Question 27

Henderson-Hasselbach equation (for extracellular pH)

Answer 27

pH = 6.1 + log [HCO3-] / 0.03 Pco2

Question 28

Physiologic dead space

Answer 28

Vd = Vt x (Paco2) - Peco2 / Paco2

Question 29

Pulmonary vascular resistance

Answer 29

PVR = P pulm artery - P L atrium / Cardiac output

Question 30

Alveolar gas equation

Answer 30

PAO2 = PIO2 - PaCO2 / R