USMLE step 1 Public Health Science Test Correct 100%

What number is in the denominator for the RATE of divorce? - Answer Per 100 marriages What number is in the denominator for the RATE of infant mortality? - Answer Per 1000 live births What is the typical RATE given in epidemiology for most cases? - Answer Per 100,000. What are most disease rates in the US for most all diseases? - Answer Less than 50 per 100,000.... Almost ALL are below 100 per 100,000 What is an INCIDENCE rate? - Answer The rate of NEW cases in a population divided by people at risk to be a case What is a PREVALENCE rate? - Answer The rate of ALL cases in a population divided by people at risk to be a case. How do you remember was an incidence rate is? - Answer IN-cidence is the rate of new IN-coming cases What type of rates should be associated with Incidence? - Answer Attack rate---you shrink the denominator as per the exposure. Create a difference 'attack rate' for every food that was eaten in a restaurant, saw, and the one with the highest rate is the culprit. (Acute conditions) What two prevalences are associated with prevalence rate? - Answer Point and Period prevalence What is point prevalence? - Answer A particular INSTANCE in time....Who has the disease over who is at risk. What is period prevalence? - Answer Period is for a larger period of time, who has it over this period over who is at risk Mortality data is by definition what type of date? - Answer Incidence data....the number of newly dead What is the general relationship between prevalence and incidence? - Answer Prevalence = incidence x duration.... If either incidence or duration increase, so does prevalence. What is a CRUDE rate? - Answer A rate that is generalized to an entire population, ie death rate in the US in 2000 What is a SPECIFIC rate? - Answer One that has been modified to have some sort of qualifier, ie male death rate in 2000... This is GENDER SPECIFIC What is a CASE fatality rate? - Answer The number of deaths from a specific cause (heart disease) divided by the number of patients with that disease. What is the Proportionate mortality rate? - Answer Deaths from a cause (heart disease) divided by all deaths. Sensitivity detects what?? - Answer DISEASE! The calculation deals with diseased people. They actually HAVE the disease.... So it is true positives divided by the rest, True positives over (TP and the false negatives) Specificity detects what?? - Answer HEALTHY people!! True negatives over all people without the disease (TN+ FP) What does PPV detect? - Answer The value of a positive test result and of course is given by the TRUE's divided by everything in the row. True positives divided by all positives, TP AND FP What does NPV detect - Answer The value of a negative test result, given by the TRUE negatives divided by all the negatigves, TN and FN How do you calculate the ACCURACY of a test? - Answer TP + TN over EVERYTHING, TP FP TN and FN As prevalence increases what happens to positive and negative predictive values? - Answer PPV goes up. More people have the disease, thus a + test result is more believable. NPV goes down. More people have the disease, fewer people are without it so a negative is less likely. There are NO direct changes on a screening test based on increased or decreased incidence.... - Answer Dur. What is the relationship between pretest probabilities of sensitivity and sensitivity WRT prevalence? - Answer NONE...Pretest values are constant and are a measure of the test itself, and will never change. What point of the double hump diagram gives you the FEWEST FALSES or the highest accuracy for a test? - Answer The point where the two curves cross...To move either direction gives you a few fewer falses in one category but a whole bunch more falses in another direction. What is the FIRST thing you need to do when constructing a 2x2 table for the USMLE? - Answer Pick a total population number and anchor is with PREVALENCE before plugging in numbers. Prevalence is the number of people in the population with disease, so for 100 people and prevalence of 20 % is 20 with disease 80 without....Then plug in the corresponding Sensitivities and Specificities. What are the four study design questions asked on USMLE questions? - Answer What type of bias is there, if any? How would you fix the bias, if any? What type of study design is this? How would you analyze data from this study? Reliability is equal to - Answer Precision... same result every time CAN have no validity tho. Validity is equal to - Answer Accuracy.... Validity implies.... - Answer Reliability... but the opposite is not always true. What is a selection bias? - Answer Where there is a nonrandom assignment to the study group... ie to study the fitness of people in NY you go to 10 local gyms in NY and take measurements.... What is selection bias AKA? - Answer Sampling bias Berkson's bias (using hospital records to estimate population parameters) Non-respondent bias--ALWAYS a problem, because this is based on people who VOLUNTEER, which is mandatory for study groups. (a convenience sample) What is the way to fix selection bias? - Answer Take a random sample or selection and weight the data to make sure it matches the population if there are any discrepancies What is measurement bias? - Answer Asking leading questions that suggest in word voice tone what the bias of the asker of the questions is. What is the Hawthorne effect? - Answer The fact of observation ITSELF changes the activity of those observed...To meet the expectations of the researcher How do you FIX the Hawthorne effect? - Answer Have a control group!--- What is the expectancy effect AKA? - Answer The Pygmalion effect What is the Pygmalion effect? - Answer Occurs when a researcher's beliefs in the efficacy of treatment changes the outcome of that treatment. What is the treatment of the Experimenter Expectancy Bias, or Pygmalion effect? - Answer Double blind studies, so neither the subject NOR the researcher knows which group is which. What is the problem with Lead-Time bias? - Answer Confusing or stating that early detection leads to an increased survival rate...That patient might very will die at the same time they would have anyway, they just knew about their disease longer. How do you fix lead time bias? - Answer Don't use the number of years survival after diagnosis as a measurement of benefit---Use life expectancy instead! What is recall bias? - Answer When a patient does not accurately recall what happened in the past, often clouded by their current knowledge or mindset. How do you fix recall bias? - Answer CONFIRM or TRIANGULATE what is told to you... What is late-look bias? - Answer Gathering information at an inappropriate time...You for the symptoms and severity of a disease, by interviewing patients with the disease but those with the worst cases are too sick or dead and cannot be interviewed...leads to a healthier outlook on the disease. How do you fix late-look bias? - Answer Stratify be severity! Make sure that you have people representing each stage of a disease so as not to leave anyone out. What is confounding bias? - Answer Occurs when the research is complicated by the fact that there is more than one factor affecting the outcome of your study...The effect of one can distort or confuse the effect of the other... How is confounding bias eliminated or fixed? - Answer Do multiple studies or do Meta-Analysis. What is a design bias?? - Answer Using two non-comparable control groups...ie having one group of hypertensives on a drug and giving a group of normotensives a placebo... How do you fix design bias? - Answer Random ASSIGNMENT of participants into groups How do you know you are looking at a Case-Report? - Answer There is one single subject....Difficult to differentiate their own personal baggage from the disease. What is a Case Series? - Answer An observational study that looks at a group of clinical subjects...the plural form of a cast report What does a Cross sectional study look at? - Answer A SINGLE point in time... What is a cross sectional study AKA? - Answer A prevalence study, because it gives you an idea of prevalence of a disease at a given time... Asks 'what is happening NOW' What can a cross sectional study show? - Answer Risk factors associated with disease, but does not establish causality and does not show incidence. What is a case-control study mainly looking at (how do you know it is a case-control study??) - Answer Compares a group of disease people with a control group that is disease free. Usually this is retrospective and asks 'What happened?' What is a case-control study trying to establish? - Answer It is looking at causality but cannot determine it definitively Does not give prevalence or incidence What is the most likely observational study I will be involved in as a physician and thus my best guess if I don't know on the USMLE? - Answer A case-control study What observational study gives the best idea of causality? - Answer A cohort study What one observational study gives incidence? - Answer A cohort study What is a cohort study? - Answer Compares a group with a given risk factor to a group without the risk factor to determine 'what will happen?' Looking to see if the risk factor increases the chance of disease....Prospective. What is a cohort study attempting to measure in numerical terms? - Answer The Relative Risk! (RR) or the Absolute Risk Smokers have a higher risk of developing COPD than nonsmokers What is a case-control study attempting to measure in numerical terms? - Answer The ODDS RATIO (OR) Patients with COPD had a higher odds of a history of smoking that those without COPD How do you calculate the Relative Risk? (Used in cohort studies) - Answer Iexposed/Iunexposed.... The incidence in the exposed group divided by the incidence in the unexposed group. Usually answers HOW MUCH MORE LIKELY (like an incidence rate ratio) How is Attributable risk calculated and what does it tell you? - Answer It is calculated by subtracting one number from the other Incidence untreated minus Incidence treated, usually a set of incidence ratios, and the result being HOW MANY MORE CASES are seen. What presentation is often seen on USMLE tests that ask you to determine Relative Risk or Attributable risk? - Answer You might have to find the incidence ratios first from a 2x2 table. Incidence is Number with disease over total number...Do that for both populations, the one with the risk factor and the one without risk factors How do you get the NNT, number needed to treat, from an attributable risk? - Answer Take the inverse of it....for every x number treated 1 person is prevented from getting the disease. What incidence rates are used in the NNH, number needed to harm? - Answer Incidence rate of the exposed minus the incidence rate in the unexposed...take this inverse and it gives NNH What observational study is the ODDS ratio used along with? - Answer A case-control study What is the formula for calculation of the odds ratio? - Answer AD/BC In the Odds ratio calculation how do you know what is the A cell? - Answer A cell is the one that has the risk factor and the disease state converging, ie smokers who got lung cancer. The D cell is diagonal to this. How should the Odds ratio truly be read? - Answer If you have THIS (colorectal cancer) you are X times more likely to have had THIS (familial history of CRC) in your past. How do you get the number one risk factor for any one disease? - Answer You do a number of odds ratios for one disease and the one that gives you the highest odds ratio is your number 1 risk factor What data analysis is used as measurement in a cross-sectional study? - Answer Chi-squared test What is an interventional study AKA? - Answer A clinical trial What is the first thing to do in the USMLE when presented with a study? - Answer Determine if it is an observational study (case-control, cohort etc...) or if it is a clinical trial, AKA interventional study. What is a phase 1 clinical trial essentially testing? - Answer SAFETY Who are phase 1 clinical trial drugs given to? - Answer Healthy volunteers What is the purpose of a phase II clinical trial? - Answer To determine protocol and dosing Who are phase II drugs given to? - Answer Patients with the disease... (Usually in the hundreds) What is phase III of a clinical trial used for? - Answer Efficacy and largely SIDE EFFECTS (with numbers usually in the thousands.) What is the purpose of the post-marketing survey? - Answer To find negative side effects of a drug once is has been clinically approved. What is the conclusion you MAY come to when a clinical trial drug involved a placebo group. - Answer Does this new drug work better than NOT GIVING A DRUG What is the conclusion you MAY come to when a clinical trial drug used a standard of care group? - Answer Does this drug work better than the OLD DRUG, the standard of care. RANDOM ASSIGNMENT IS NOT SMOOTH AND LINEAR... - Answer Alternating 1 group than the other group is NOT random assignment. What is important to remember about a double blind study!? - Answer NEVER BREAK THE CODE UNLESS YOU ARE CLOSING DOWN THE STUDY, because breaking the code WILL end the study. What is a community trial essentially testing? - Answer Does this drug work outside of the hospital/clinical setting... Usually they are in a phase III clinical trial at this time. What does a cross-over study automatically implicate? - Answer Double blind design What is the underlying principle of a crossover design study? - Answer There is a double blind design and first one group get the drug, while the other gets the placebo and at some point, also double blinded, the groups switch...everyone gets the drug at some point. How do you calculate the probability of independent events (as in a coin toss?) - Answer Multiple the probabilities ... 1/2 chance of getting a heads on a coin toss...1/2 x 1/2 is the probability of getting two heads in a row. How do you calculate the probability of mutually exclusive events? - Answer You add them. The probability of getting a HEADS or a TAILS on a coin toss is .5 + .5 = 100 percent. If the chance of having diabetes is 10 percent and the chance of being obese is 30 percent the chance of being obese OR diabetic is 40 % How do you calculate the odds of two non-mutually exclusive events? - Answer Multiply the two odds together and subtract that number from the sum of the two numbers What is the percentage of American households today where the male works, the female stays home with the children, and there are 2 kids? - Answer 15%....The 'typical American Family' is no longer typical. What does having children do to the rate of marital satisfaction? - Answer Decreases it. What are the underlying determinants of socio-economic status? - Answer Combination of Education and Occupation...NOT money, wealth or income DRUG pushers have lots of money but low SES Priests have high SES but...little money How much higher is rate of breast cancer in homosexual women than in heterosexual? - Answer 8x! Due to the fact that if they have children, it is usually later in life. What are high SES people more at risk for? - Answer Bipolar disorders Anxiety disorders Breast Cancer (marry later and have children later) What attributes are low SES people more likely to have? - Answer More rigid sex gender roles More rigid individual expectations (this is MY way and it is the RIGHT way) Action-oriented language What is the annual suicide completion rate in the US? - Answer 30,000 people...compared to 600,000 attempts. What is the most likely method by which either MAN or WOMAN COMPLETE suicide!? - Answer Firearm What is the most likely method of attempted suicide for females? - Answer Pill OD. or poison What is the suicide rate for adults in the US? - Answer 11 per 100,000 Is it normal for an adolescent to have considered suicide in the past? - Answer Yes, as much as 54% of adolescents. Is it normal for an adolescent to have known a friend who committed suicide? - Answer Yes, as much as 60% How among all adolescents is most likely to commit suicide? - Answer Native Americans During what age range are Native Americans most likely to kill themselves? - Answer 15-19, during adolescents....Contrast this to the ELDERLY who are most likely in any other ethnicity What is true about almost all adolescents that have killed themselves? - Answer They had some underlying, undetected mental health issue. The way to prevent adolescent suicide is to screen for mental health problems and treat them. What are the top 4 mental diagnosis of people likely to commit suicide? - Answer Depression=Alcoholics> Schizophrenics> Borderline Personality Disorder Highest physician subspecialty that is likely to commit suicide? - Answer Psychiatry What is Serotonin's role in suicidal behavior? - Answer Serotonin is thought to be an impulse control mechanisms, so that someone with low serotonin is more likely to commit suicide. What is the number one risk factor for suicide completion? - Answer Previous suicide attempt Who is at greatest risk for suicide? - Answer Elderly white males What months are suicide most likely? - Answer April thru September...BECAUSE its nice out, beautiful and the person has nothing to blame other than themselves for the way they feel. Same reason that people with high SES are at higher risk...you have better things than most people, the world is pretty good. Must be you. What do you say to a patient thinking about suicide to find out if they have a plan? - Answer 'Before when you said you have thought about suicide...tell me, what do you think about when you think about suicide. On the STEP exam do NOT help a patient kill themselves... - Answer Even if they are 95 and dying of cancer.... Dont do it. Number one cause for a man to visit the physician in the US? - Answer Hypertension Number one cause for a woman to visit the physician in the US? - Answer Pregnancy What is the number one killer in America? - Answer Heart Disease Most hospitalizations in the US are due to... - Answer Psychiatric reason Most days in the hospital are attributed to - Answer Diseases of the cardiovascular system. Most days lost from work in the US are caused by... - Answer Diseases of the Upper respiratory system Most common work-related disability in the US is for... - Answer Musculo-skeletal problems... Back pain is number one for both genders, followed by carpal tunnel for both genders. Most common cause of visits to an ambulatory clinic in the US is for... - Answer Back pain What type of payment is CAPITATION? - Answer Pre-payment for the number of patients you are responsible for, whether or not they are sick or healthy, ALTHOUGH the healthier they are the more patients you can take on. What three groups of people are covered by Medicare in the US? - Answer The elderly (over 65) The disabled AND the dependents of disabled What are three things that you might expect are covered by Medicare, which in fact are not?? - Answer Prescription drugs (unless you buy Medicare D) Physical exams Nursing Home Care Medicare - Answer CARE for the elderly MedicAID - Answer AID for the poor..usually it is MedicAID that is paying for nursing home care Most dangerous sexual practice that puts you at risk for AIDS - Answer Anal sex...can be transmitted via oral sex Most likely person to engage in anal sex, hetero or homosexual?? - Answer Heterosexual, there are FAR more in the US Pt post MI ask you how long they should wait until having sex with their wife, you say.... - Answer Whenever you feel comfortable with it OR Whenever a stress test indicates that it is OK (like climbing a flight of stairs.) What sexual position is LEAST stressful on someones heart for someone post MI? - Answer Pt flat on their back, with partner on top. If your patient has AIDS today, what is most likely tru about that patient? - Answer The are homosexual or Bisexual Your patient just seroconverted and they are HIV positive, what is most likely true about your patient? - Answer They are an IV drug user What is the fastest method of HIV transmission today? - Answer Heterosexual Contact Uncircumcised males are 8x more likely to contract AIDS than circumcised males... - Answer Area under the foreskin is particularly vulnerable. What is the most quoted rate of risk for contracting HIV from an HIV + needle stick? - Answer 1 in 250 What is the rate of risk associated with having unprotected sex with a member of a high risk group for AIDS (single sexual encounter.) - Answer 1 in 2 to 1 in 20 will contract AIDS... Compare this to 1 in 5 million for a non-high risk group Most likely cause of a medical professional having HIV/AIDS? - Answer Unprotected sex....multiple needle sticks still give you less of a risk than 1 unprotected episode with a high risk partner Risk of seroconverting after having been transfused with HIV positive blood? - Answer 2 in 3 If an HIV positive mother gives birth, what is the chance of her baby testing HIV positive at birth? - Answer 100% due to mothers antibodies...only about 20% finally seroconvert after a year. Should an HIV positive patient breastfeed her newborn? - Answer NO, increases risk of transmission up to 50%. Standard Operating Procedure for an HIV mother who is about to give birth? - Answer NEVIRAPINE! One dose to the mother in labor and one dose to the child reduces risk of HIV transmission to 10%