Rapid Review: 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

p² + 2pq + q² = 1

p + q = 1

Question 12

Volume Of Distribution

Answer 12

V_d = Amount Of Drug In The Body / Plasma Drug Concentration

Question 13

Half-Life

Answer 13

t_½ = 0.7 x V_d / CL

Question 14

Drug Clearance

Answer 14

CL = Rate Of Elimination Of Drug / Plasma Drug Concentration

CL = V_d X K_e (Elimination Constant)

Question 15

Loading Dose

Answer 15

LD = C_p x (V_d / F)

Question 16

Maintenance Dose

Answer 16

MD = C_p x (CL / F)

Question 17

Cardiac Output

Answer 17

CO = Rate Of O₂ Consumption / Arterial
O₂ Content - Venous O₂ Content

CO = Stroke Volume x Heart Rate

Question 18

Mean Arterial Pressure

Answer 18

MAP = Cardiac Output x Total Peripheral Resistance

MAP = 2/3 Diastolic + 1/3 Systolic

Question 19

Stroke Volume

Answer 19

SV = CO / HR = EDV - ESV

Question 20

Ejection Fraction

Answer 20

EF = SV / EDV = EDV - ESV / EDV

Question 21

Resistance

Answer 21

Resistance = Driving Pressure (ΔP) / Flow (Q)

= 8η (Viscosity) x Length / πr⁴

Question 22

Net Filtration Pressure

Answer 22

P_net = [(P_c - P_i) - (π_c - π_i)]

J_v = Net Fluid Flow = (K_f) (Pnet)

Question 23

Renal Clearance

Answer 23

C_x = U_xV / P_x

Question 24

Glomerular Filtration Rate

Answer 24

GFR = U_inulin x V/P_inulin = C_inulin

GFR = K_f [(P_GC - P_BS) - (π_GC - π_BS)]

Question 25

Effective Renal Plasma Flow

Answer 25

ERPF = U_PAH x V / P_PAH = C_PAH

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

V_D = V_T 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