[a/(a+b)]/[c/(c+d)]
Cohort Studies
(Risk of developing disease in exposed group)/(risk in unexposed group)

ad/bc
Case-Control Studies
Odds that the group with the disease was exposed to risk factor (a/c)/(Odds that the group without disease was exposed (b/d)

Investigator is affected by prior knowledge

Exposure-disease relationship can be explained by another variable

Apparent prolongation of survival because of earlier diagnosis

Inaccurate pt recall

Subjects selected biasedly or biased from selective loss of follow up

Observational

Retrospective

Compare groups of people w/ and w/o disease and look for prior exposure or risk factors

"What Happened?"

Odds Ratio

Observational

Prospective or Retrospective

Compare a group with a given exposure or risk factor to a group w/o it and look if exposure ↑ likelihood

Who will or Who has developed disease

Relative Risk

Observational
Right Now
Collect data from a group of people to assess frequency of disease and relative risk at a particular point in time
“What is happening?”
Prevalence, Relative Risk, Can show Risk Factor Association but not causality

Compares frequency with which monozygotic or dizygotic twins develop the same disease
Measures Heritability

Compares siblings raised by biological vs adoptive parents
Heritability and influence of environmental factors

Experimental study involving humans
Compares therapeutic benefits of 2 or more treatments or treatment and placebo
Randomized, Controlled, and Double Blinded studies are better

Double: Patients and Doctors do not know whose getting treatment
Triple: Researchers analyzing data do not know who got treatment

Small # of health volunteers
Assesses safety, toxicity, and pharmacokinetics

Small # of patients w/ disease
Assesses treatment efficacy, optimal dosing, and adverse effects

Large # of patients comparing 2 drugs or placebo
Compares new treatment to current treatment

Postmarketing surveillance trial of patients after approval
Detects rare or long term adverse effects

"SNOUT - SeNsitivity rules OUT"

"PID - Positive In Disease"

True Positive Rate

a/(a+c) = 1-(false neg rate)

Rules out disease

Used for screening in diseases w/ low prevalence

"SPIN - SPecificity rules IN"

"NIH - Negative In Health"

True Negative Rate

d/(d+b) = 1-(false pos rate)

Rules in disease

Confirmatory test after positive screening test

Proportion of + tests that are true positives
a/(a+b)
Varies directly with prevalence or pretest probability: high pretest probability –> high PPV

Proportion of negative test results that are true negative
d/(c+d)
Varies inversely with prevalence or pretest probability: High pretest probability –> low NPV

(New cases over specified period)/(Population at risk)

(Existing cases)/(Population at risk)
Incidence x Average disease duration

Prevalence > Incidence

When prevalence is low

[a/(a+b)]-[c/(c+d)]

| Risk in exposed group - Risk in unexposed group

c/(c+d) - a/(a+b)

| Event rate in placebo minus treatment groups

Number of pts who need to be treated for 1 patient to benefit
1/(absolute risk)

Number of pts who need to exposed to a risk factor for 1 pt to be harmed
1/(attributable risk)

Consistency and reproducibility of a test. The absence of random variation
Random error ↓ precision
↑ precision --> ↓ SD

Trueness of test measurements (validity)
Absence of systematic error or bias in the test
Systemic error ↓ accuracy

Subjects not representative of the general population

| A form of selection bias

Information gathering at an inappropriate time (i.e. survey to study a fatal disease - only those still alive will be able to answer survey)

Subjects in different groups are not treated the same way

Group being studied changes behavior because they know they are being studied

Mean = Median = Mode

σ
(+1σ) and (-1σ) account for 68% of n
(-2σ) to (+2σ) account for 95% of n
(-3σ) to (+3σ) account for 99.7% of n

σ/√n

| SEM will ↓ as n ↑

Mean > Median > Mode
Mode is least affected by outliers in the sample
Asymmetrical distribution with long tail on right

Mean < Median < Mode

| Asymmetry with longer tail on left

There is no association between the disease and the risk factors (H0)
There is some association between the disease and the risk factor (H1)

α
Error of stating there is a difference when there is not. Accepting H1 and rejecting H0 when H0 is true.
False-Positive Error
Used to calculate p

β
Error that there is not an effect or difference when one exists. Accept H0 when H1 is true
False-Negative Error

1-β
Probability of rejecting H0 when it is false
Increases with ↑ Sample Size, Expected Effect Size, and Precision of measurements

Pools data and integrates results from several similar studies
↑ statistical power
Limited by quality of individual studies or bias in each study

Range of values in which a specified probability of the means of repeated samples would be expected to fall
Range from [mean - Z(SEM)] to [mean + Z(SEM)]
95% CI corresponds to p=.05
CI = 95%, Z = 1.96
CI = 99%, Z = 2.58

There is no significant difference and H0 is accepted

H0 is not rejected

Significant difference exists

No significant difference

Checks differences between the means of 2 groups

Checks difference between the means of 3 or more groups

Test checks difference between 2 or more percentages or proportions of categorical outcomes (not mean values)

r
-1 to +1
The closer it is to 1, the stronger the linear correlation between 2 variables

r^2

"PDR"
Prevent occurrence
early Detection
Reduce disability from disease

For the Elderly (≥65)

For the Destitute

Respect pt as individuals and honor their preferences

Fiduciary duty to act in patient's best interests

Do no harm

Treat persons fairly

Emancipated (married, self supporting, has children, in the military), Emergency, Contraception, Treating STDs, Pregnancy, Treatment of Drug Addiction

Not if the patient demonstrates decision making capacity

Harm to others, harm to self, and physician can prevent harm

Many states require parental notification or consent for minors for an abortion. Unless she is at medical risk, do not advise pt to have an abortion regardless of her age or condition of the fetus

No Way! but can give medically appropriate analgesics that coincidentally shorten the pt's life

Patient can be hospitalized involuntarily

Do not offer falsely reassuring statements like "you still look good"

Do not explain delay. Just apologize and acknowledge

Must tell patient

Suggest the pt speak directly with the doctor

Say you will speak with that person

1 minute and 10 minutes
Appearance, Pulse, Grimace, Activity, Respiration
Greater than or Equal to 7 is good.
4-6: assist and stimulate
Less than 4: resuscitate
If <4, there is ↑ risk of long term neurological damage

Less than 2500g
Prematurity or intrauterine growth retardation
"PREME C SHIT"
↑ risk for SIDS and overall mortality
Impaired thermoregulation and immune function, Hypoglycemia, Polycythemia, Impaired neurocognitive/emotional development
Infections, RDS, Necrotizing enterocolitis, Intraventricular hemorrhage, persistent fetal circulation

Rooting reflex, holds head up, Moro reflex disappears
Social smile
Orients and responds to voice

Sits alone, Crawls, Transfers toys from hand to hand
Stranger anxiety
Responds to name and simple instructions, uses gestures, plays peek-a-boo

Walks, Babinsky Sign Disappears
Separation anxiety
Few words

Climbs stairs, Stacks 3 blocks at 1 year, Stacks 6 blocks at 2 years
Rapprochement
200 words. 2 word phrases at age 2

Feeds self with fork and spoon. Kicks ball
Core gender identity. Parallel play
Toilet training (pee at 3)

Rides tricycle (3 cycle at 3). Copies line or circle drawings
Comfortably spends part of the day away from mother
900 words. Complete sentences

Uses buttons and zippers, Grooms self, Hops on 1 foot, Makes simple drawings
Cooperative play, Imaginary friends
Can tell detailed stories and uses prepositions.

Interest does not ↓
Men have slower erection, ejaculation, longer refractory period
Women have vaginal shortening, thinning and dryness

Intelligence does not decrease

↓ REM and slow-wave sleep. ↑ latency and awakening

↑ suicide rates

| Men 65-74 have highest rates in US

↓ Vision, Hearing, Immune response, Bladder control, Renal, Pulmonary, GI
↓ muscle, ↑ fat

Shock, Denial, Guilt, Somatic symptoms. May experience illusions
Up to 1 year

Excessive, prolonged (>1 year), delayed, inhibited, or denied grief
May experience depression, delusions, and hallucinations

Drugs, Disease (depression, diabetes), Psychological

(Wt in kg)/(Height in meters)^2
Less than 18.5 is underweight
25 to 29.9 is overweight
Greater than 30 is obese

Alert and active

| Beta (highest frequency, lowest amplitude)

Alpha

5%
Light Sleep
Theta

45%
Deeper sleep; Bruxism
Sleep Spindles and K complexes

25%
Deepest non REM sleep
Delta waves (low frequency, high amplitude). Slow wave sleep
Sleepwalking, night terrors, bedwetting

25%
Dreaming, Loss of motor tone, Memory processing, Erections, ↑ brain O2 use
Beta waves

"BATS Drink Blood"

| Beta, Alpha, Theta, Sleep spindles, Delta, Beta

5HT region of Raphe Nucleus

Oral Desmopressin

| Preferred over Imipramine

EtOH, Benzodiazepines, Barbituates

| Also reduce Delta sleep

Benzodiazepines

Every 90 minutes

Duration ↑ throughout night

↓ frequency with age

ACh --> REM. NE --/ REM

↑ and variable BP and HR. EOM (activity of PPRF), Penile/Clitoral Tumescence

↓ slow wave sleep, REM latency,
↑ REM early in sleep, ↑ total REM sleep
Repeated nighttime awakening
Early-morning awakening

Disordered regulation of sleep-wake cycles
Daytime sleepiness, Hallucinations (right before or after sleep), Cataplexy following strong emotional stimulus. Cannot move when you wake up in the morning
REM at beginning of sleep
Strong genetic components
Daytime stimulants (amphetamines, modafinil) and nighttime GHB (sodium oxybate)

Suprachiasmatic nucleus (SCN) of the hypothalamus
Controls ACTH, Prolactin, Melatonin, and nocturnal NE release
SNC --> NE release --> Pineal gland --> melatonin

SCN regulated by environment (light)

Periods of terror with screaming in the middle of the night

Slow-wave, non-REM sleep

Children

No memory of event

emotional distress, fever, lack of sleep

Self limited