Statistics and Data

National Center for Health Statistics (NCHS), CDC

federal agency that states report their local data on births, deaths, and vital statistics to; conducts surveys on health status, lifestyle, and heath-related behaviors

Vital Statistics

birth certificate, death certificate, marriages/divorces, spontaneous fetal deaths (abortions), infant deaths before 1st birthday

Birth Certificate

issued by local government, reported to state and NCHS, contains family and medical information

Death Certificate

tells cause of death

Census

taken by U.S. Census Bureau every 10 years, takes numbers of population that are necessary to calculate rates

What the Census Surveys

geographic distribution, sex, age, ethnic characteristics, education, housing, health insurance, trends in immigration and emigration

Calculated Statistics and Rates

birth rates, mortality rates, age-adjusted mortality rate, age-specific mortality rate, infant mortality rate, life expectancy, years of potential life lost

Infant Mortality Rate

death before 1st birthday/total live births

Life Expectancy

average number of years left to individuals of certain age

Years Potential Life Lost

death under 75 years is considered premature

Surveys

National health interview survey, national heath and nutrition examination survey, behavioral risk factor survey

National Health Interview Survey

50,000 households

National Health and Nutrition Examination Survey (NHANES)

comprehensive health assessment of 15 counties, 5,000 people

Behavior Risk Factor Survey (BRFS)

states conduct and report to CDC, risk factors and preventative care

Uses of Data

detect health issues in the population, development of public health policy, plan allocation of resources to address community needs, evaluate efficacy of public health interventions

Confidentiality

removal of identifying information, restricted access to databases, IRB reviews requests for access to data by researchers

Uncertainty and Probability

studies measure probability, confidence interval, power, false positives and false negatives

Degree of Probability: p value

determines if the observed result could have happened by chance, P = 0.05 means there is a 5/100 probability the experimental result occurred by chance

Statistically Signifcant

p = 0.05

Confidence Interval

range of values where the true value falls, margins of error, when the CI is lower, there is a lower likelihood of random error

Power

probability of finding an effect, large numbers overcome random chance, statisticians can calculate necessary study size

Screening Tests

may yield false positives or false negatives

Sensitive Screening Tests

few false negatives

Spec

Population Screening Tests

want to avoid missing any positives, sacrifice specificity for sensitivity, follow-up with more specific test, high number of false positives may render test ineffective or too costly

Covid-19 Screening Tests

tests for virus and antibody, diagnostic test for virus, test for exposure and immune response, Abbot Test ID Now Rapid Test

Test for Exposure and Immune Response

pressure of reactive antibodies in blood

Pressure on FDA to get Test Kits Deployed

emergency authorization, little data available on performance, companies now being asked to do follow up accuracy studies

Emergency Authorization

lower standards, shorter time, ‘may be effective’

Abbot Test ID Now Rapid Test

15 minutes, screens for virus

NYU Study: Covid Screening Test

indicated false negatives in 1/3 to ½ of cases, disputed by Abbot: 90-95% accurate, supported by studies at Stanford, Loyola, and Cleveland Clinic

Analytical Sensitivity

likelihood test will not miss pathogen, minimum concentration of pathogen the test can detect

Clinical Test Performance

how test accurately diagnoses using clinical specimens, requires a reference standard

Clinical Sensitivity

percent of positive tests among patients with confirmed disease

Reference Standard

independent confirmation of disease by symptoms of another test

Covid Testing Challenges

diagnostic testing for opening country required tests to be highly sensitive, FDA must ensure clinical sensitivity and specificity before giving authorization to market, doctors must be careful with false negative test results when patient presents clinical symptoms

Covid Testing Challenges: Diagnostic Testing

will not miss positive cases in screened population, low false negatives, can tolerate false positives, test must be able to detect asymptomatic individuals who may be contagious

Cost Benefit Analysis

estimated cost of implementing policy vs estimated benefit, long term vs short term costs and benefits, can’t serve as the primary determinant of a health care decision

Cost Benefit Analysis: Implementing Policy vs Estimated Benefit Example

costs of immunization program vs cost of treating disease