Equation Review Flashcards
Sensitivity
Sensitivity = TP / (TP + FN)
Specificity
Specificity = TN / (TN + FP)
Positive predictive value
PPV = TP / (TP + FP)
Negative predictive value
NPV = TN / (FN + TN)
Odds ratio (for case-control studies)
Odds ratio = (a/c)/(b/d) = ad/bc
Relative risk
Relative risk =[a/(a + b)] / [c/(c + d)]
Attributable risk
Attributable risk = a/(a+b) − c/(c + d)
Number needed to treat
1/absolute risk reduction
Number needed to harm
1/attributable risk
Hardy-Weinberg equilibrium
p2 + 2pq + q2 = 1
p + q = 1
Volume of distribution
Vd = amount of drug in the body / plasma drug concentration
Half-life
t1/2 = (0.693 × Vd) / CL
Drug clearance
CL = rate of elimination of drug / plasma drug concentration = Vd × Ke (elimination constant)
Loading dose
LD = (Cp × Vd) / F
Maintenance dose
MD =(Cp × CL × τ) / F
Cardiac output
CO = rate of O2 consumption / (arterial O2 content − venous O2 content)
CO = stroke volume × heart rate
Mean arterial pressure
MAP = cardiac output × total peripheral resistance
MAP = 2 ⁄3 diastolic + 1 ⁄3 systolic
Stroke volume
SV = EDV – ESV
Ejection fraction
EF = SV / EDV = (EDV − ESV) / EDV
Resistance
Resistance = driving pressure (ΔP) / flow (Q) = (8η (viscosity) × length) / πr4
Net filtration pressure
Pnet = [(Pc − Pi) − (πc − πi)]
Jv = net fluid flow = (Kf)(Pnet)
Renal clearance
Cx = Ux V / Px
Glomerular filtration rate
GFR = Uinulin × V / Pinulin = Cinulin
GFR = Kf [(PGC – PBS) – (πGC – πBS)]
Effective renal plasma flow
ERPF = UPAH × (V / PPAH) = CPAH
Renal blood flow
RBF = RPF / (1 − Hct)
Filtration fraction
FF = GFR / RPF
Henderson-Hasselbalch equation (for extracellular pH)
pH = 6.1 + log([HCO3−] / 0.03 PCO2)
Winters formula
PCO2 = 1.5 [HCO3–] + 8 +/- 2
Physiologic dead space
VD = VT × (PaCO2 − PECO2) / PaCO2
Pulmonary vascular resistance
PVR = (Ppulm artery – PL atrium) / cardiac output
Alveolar gas equation
PAO2 = PIO2 – PaCO2 / R
