Equations Flashcards
(26 cards)
Sensitivity
sensitivity = TP/(TP + FN) = 1 - FN rate
TP= true positive; FN = false negative
Specificity
specificity = TN/(TN + FP) = 1 - FP rate
Positive Predictive Value
PPV = TP/(TP+FP)
Negative Predictive Value
NPV=TN/(TN+FN)
Relative Risk
R=[a/(a+b)]/[c/(c+d)]
Attributable Risk
AR=[a/(a+b)] - [c/(c+d)]
*AR - difference in risk between exposed and unexposed groups, or the proportion of disease occurrences that are attributable to the exposure (ie smoking causes 1/3rd of cases of pneumonia)
Number needed to treat =
1/absolute risk reduction
*Absolute risk reduction - reduction in risk associated with a treatment compared to a placebo
Number needed to harm =
1/attributable risk
Hardy-Weinberg equilibrium =
p^2 + 2pq + q^2 = 1
p+q = 1
- p^2 - frequency of homozygosity for allele p
- q^2 - frequence of homozygosity for allele q
- 2pq - frequency of heterozygosity (carrier frequency)
Henderson-Hasselbach equation =
pH = pKa + log [HCO3-]/(0.3XPCO2)
Volume of distribution
Vd= (amount of drug in body)/(plasma drug concentration)
Clearance
CL = rate of elimination of drug/plasma drug concentration
Half-Life
t1/2 = (0.7XVd)/CL
Loading dose
LD = Cp X (Vd/F)
- Cp=target plasma concentration
- F=Bioavailability = fraction of administered drug that reaches circulation (if IV, F=100%; if oral, F=% that survives first pass in liver or gut)
Maintenance dose
MD = Cp X (CL/F)
Cardiac output
CO = rate of O2 consumption/ (arterial O2 content - venous O2 content)
-AND-
CO = stroke volume X heart rate
Mean Arterial Pressure
MAP = CO X total peripheral resistance
-AND-
MAP = 1/3 systolic + 2/3 diastolic
`Stroke Volume
SV = end diastolic volume - end systolic volume
Ejection Fraction
EF = (Stroke volume/End diastolic volume) X 100
Resistance
R = driving pressure / flow
= (8 X viscosity X length) / (pi X r^4)
Net filtration pressure
Pnet = [(Pc-Pi) - (rc - ri)]
- Pc=capillary pressure –> pushes fluid out of capillary
- Pi=interstitial fluid pressure –> pushes fluid into capillary
- rc= (r should be sigma) plasma colloid osmotic pressure –> pushes fluid into capillary
- ri= interstitial fluid colloid osmotic pressure –> pushes fluid out of capillary
Glomerular filtration rate
GFR= Uinulin X (V/Pinulin) = Cinulin
= (urine concentration X urine flow) / Plasma concentration
- Uinulin = urine inulin
- Pinulin = plasma inulin
- Cinulin = clearance of inulin
- V = urine flow rate
-AND-
GFR = Kf [(PGC - PBS) - (rGC - rBS)]
- GC = glomerular capillary
- BS = Bowman’s space
- rBS - normally equals 0
*** Normal GFR = 100 mL/min
Effective renal plasma flow
ERPF = Upah X (V/Ppah) = Cpah
Renal blood flow
RBF = RPF / (1-Hct)
