Rapid Review - Equations

Question 1

Sensitivity

Answer 1

TP/ (TP + FN)

Question 2

Specificity

Answer 2

TN/ (TN + FP)

Question 3

Positive Predictive Value

Answer 3

TP/ (TP + FP)

Question 4

Negative Predictive Value

Answer 4

TN/ (TN + FN)

Question 5

Odds Ratio (for case control studies)

Answer 5

A/C / B/D = AD/BC

Question 6

Relative risk

Answer 6

[A/(A+B)] / [C/(C+D)]

Question 7

Attributable risk

Answer 7

[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

BMI

Answer 10

weight in kg/(height in meters^2)

Question 11

Hardy-Weinberg equilibrium

Answer 11

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

p + q = 1

Question 12

Volume of Distribution

Answer 12

Vd = amount of drug in body/ plasma drug concentration

Question 13

Half life

Answer 13

(0.7xVd)/ CL

Question 14

Clearance

Answer 14

rate of elimination of drug/ plasma drug concentration

Vd * Ke (elimination constant)

Question 15

Loading Dose

Answer 15

Cp * (Vd/F)

plasma concentration * volume of distribution/bioavailability

Question 16

Maintenance Dose

Answer 16

Cp * (CL/F)

plasma concentration * clearance/bioavailability

Question 17

Cardiac Output

Answer 17

SV * HR or

Rate of O2 consumption/ (Arterial - Venous O2 content)

Question 18

Mean Arterial Pressure

Answer 18

CO * TPR or

2/3 diastolic + 1/3 systolic

Question 19

Stroke volume

Answer 19

CO/HR or

EDV - ESV

Question 20

Ejection fraction

Answer 20

SV/ EDV or

(EDV - ESV)/EDV

Question 21

Resistance

Answer 21

change in P/Q = change in pressure/flow or

8nl/(pir^4) [n=viscosity]

Question 22

Net Filtration Pressure

Answer 22

[(Pc-Pi)] - (Pi-c - Pi-i)

Kf(Pnet)

Question 23

Renal clearance

Answer 23

CL = Urine concentration * Volume/Px

Question 24

GFR

Answer 24

Uinulin * V/Pinulin = Cinulin

Kf [(Pressure GC - Pressure Bowman space) - (Pi GC - Pi BS)]

Question 25

Effective Renal Plasma Flow

Answer 25

U PAH * V/P PAH = CPAH

Question 26

Renal Blood Flow

Answer 26

RPF/ (1-Hct)

Question 27

Filtration fraction

Answer 27

GFR/RPF

Question 28

Henderson-Hasselbach equation (for extracellular pH)

Answer 28

pH = 6.1 + log [HCO3-]/0.03 PCO2

Question 29

Physiologic Dead Space

Answer 29

VD = VT * [(PaCO2) - (PECO2)]/PaCO2

Question 30

Pulmonary Vascular Resistance

Answer 30

(Pulmonary A. Pressure - Left Atrium Pressure) / CO

Question 31

Alveolar gas equation

Answer 31

PAO2 = PIO2 - (PaCO2/R)