Equations Flashcards
Sensitivity
Proportion of all people with disease who test positive
Does not vary with diesase prevelance
Specificity
Proportion of all people without disease to test negative
Does not vary with disease prevelance
Positive predictive value
Proportion of test results that are true positive
PPV and NPV vary with disease prevelance
Negative predictive value
Proportion of negative test results that are true negative
PPV and NPV vary with disease prevelance
Relative risk
Probabilty of getting a disease in the exposed group divided by the probability of getting a disease in the unexposed group
Measure of Cohort studies
Attributable risk
Difference in risk between exposed and unexposed groups of getting the disease
Number needed to treat
(Number needed to treat to prevent 1 more disease case)
Ideal NNT =1 (everyone treated gets cured)
Number needed to harm
(Number of people who need to exposed to risk factor to cause 1 more disase case)
Very bad NNH = 0
Hardy-Weinberg equalibrium
Henderson-Hasselbach equation
Volume of distribution
Clearance
Half-life
Loading dose
Maintenance dose
Cardiac output
(2 equations)
CO= Stroke volume * Heart Rate
Mean arterial pressure
Stroke volume
Ejection fraction
Normal Ejection fraction > 55%
Arterial resistnace
Directly proportional to viscosity and length
Indrectly proportional to radius4
Net filtration pressure
Glomerular filtration rate
(2 equations)
GFR = Kf [(PGC - PBS) - πGC - πBS)]
Effective renal plasma flow
Renal blood flow
Filtration fraction
Physiologic dead space
Odds ratio
Odds of having disease in exposed group divided by odds of having disease in unexposed group
Measure of Case-Control studies
Odds ratio = (a/b) / (c/d)
Winter’s formula
Respiratory compensation in metabolic acidosis
PCO2 = 1.5 (HCO3-) + 8
(+/- 2)
A-a gradient
PAO2 = 150 - (PaCO2/0.8)
A-a gradient = PAO2-PaO2
Normal (10-15mmHg)
