Flashcards in Equations Deck (26)
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1
Sensitivity
sensitivity = TP/(TP + FN) = 1 - FN rate
(TP= true positive; FN = false negative)
2
Specificity
specificity = TN/(TN + FP) = 1 - FP rate
3
Positive Predictive Value
PPV = TP/(TP+FP)
4
Negative Predictive Value
NPV=TN/(TN+FN)
5
Relative Risk
R=[a/(a+b)]/[c/(c+d)]
6
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)
7
Number needed to treat =
1/absolute risk reduction
*Absolute risk reduction - reduction in risk associated with a treatment compared to a placebo
8
Number needed to harm =
1/attributable risk
9
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)
10
Henderson-Hasselbach equation =
pH = pKa + log [HCO3-]/(0.3XPCO2)
11
Volume of distribution
Vd= (amount of drug in body)/(plasma drug concentration)
12
Clearance
CL = rate of elimination of drug/plasma drug concentration
13
Half-Life
t1/2 = (0.7XVd)/CL
14
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)
15
Maintenance dose
MD = Cp X (CL/F)
16
Cardiac output
CO = rate of O2 consumption/ (arterial O2 content - venous O2 content)
-AND-
CO = stroke volume X heart rate
17
Mean Arterial Pressure
MAP = CO X total peripheral resistance
-AND-
MAP = 1/3 systolic + 2/3 diastolic
18
`Stroke Volume
SV = end diastolic volume - end systolic volume
19
Ejection Fraction
EF = (Stroke volume/End diastolic volume) X 100
20
Resistance
R = driving pressure / flow
= (8 X viscosity X length) / (pi X r^4)
21
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
22
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
23
Effective renal plasma flow
ERPF = Upah X (V/Ppah) = Cpah
24
Renal blood flow
RBF = RPF / (1-Hct)
25
Filtration fraction
FF = GFR / RPF
26
