Rapid Review - Equation Review

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 / (FN + TN)

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

Hardy-Weinberg equilibrium

Answer 10

p^2 + 2pq + q^2 = 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 1/2 = 0.693 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

D = Cp x CL x tao / 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 x 1/3 systolic

Question 18

Stroke volume

Answer 18

SV = EDV - ESV

Question 19

Ejection fraction

Answer 19

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

Question 20

Resistance

Answer 20

Resistance = driving pressure (delta P) / flow (Q) = 8(viscosity) x length / (pi)r^4

Question 21

Net filtration pressure

Answer 21

P net = [(Pc - Pi) - (pi c - pi i)]; 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[(P gc - P bs) - (pi gc - pi bs)]

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

Winters formula

Answer 28

PCO2 = 1.5 [HCO3-] + 8 +/- 2

Question 29

Physiologic dead space

Answer 29

Vd = Vt x (PaCO2 - PeCO2)/PaCO2

Question 30

Pulmonary vascular resistance

Answer 30

PVR = (P pulm artery - P L atrium) / cardiac output

Question 31

Alveolar gas equation

Answer 31

PAO2 = PIO2 - PaCO2/R