# Epidemiology Quiz 2 Terms

## 39 terms · CNL 9 Epidemiology

### Underlying cause of death

the disease or injury which initiated the train of morbid events leading directly or indirectly to death or the circumstances of the accident or violence which produced the fatal injury.

### Cohort effect

examination of changes in mortality of people born in the same period of time.

### DALY (disability adjusted life year)

which is years of life lost to premature death and years lived with a disability of specified severity and duration; 1 lost year of healthy life = 1 DALY. Daly assesses the burden of disease.

### Annual Mortality rate

total number of deaths from all causes in 1 year divided by the number of persons in the population at midyear multiplied by 1000.

### Crude (unadjusted) mortality rate

the overall mortality rate, without adjustments for age, race, or other factors.

### Specific mortality rate

the mortality rate with a restriction included, such as age, race, period of time, disease, etc., such as an age- specific mortality rate. Those in the denominator must be able to be part of the numerator to be considered an at- risk population. Example: Deaths from CA in one year in 10 to 12 year olds divided by the population of 10 to 12 year olds at midyear

### Direct age- adjustment

when comparing two or more populations, a standard population number is applied, rather than specific age figures, to eliminate any differences in data caused by age. Often, the Year 2000 Standard Population is used currently.

### Indirect age adjustment

age specific rates for a population are applied to each age group in the population of interest, which will yield the number of expected deaths in each age group in the population of interest.

### Standardized mortality ratio

the observed (actual) number of deaths per year, divided by the expected number of deaths per year. # of deaths > 100 = deaths exceeded number expected; # of deaths <100 = deaths below number of expected.

### Case -fatality rate

the number of deaths from a disease after diagnosis, during a period of time, divided by the total population diagnosed with the same disease. Indicates the severity of the disease.

### Proportionate mortality

the proportion of deaths from a certain disease compared to deaths from all diseases. This is not a rate, but rather a comparison (percentage) of all deaths.

### Specificity (of a test)

ability of the test to accurately identify negative results (those who do not have the disease or abnormality).

### Sensitivity (of a test)

ability of the test to accurately identify positive results (those who do have the disease or abnormality).

### Net specificity

the gain or loss in specificity after running two tests in sequence.

### Net sensitivity

the gain or loss in specificity after running two tests in sequence.

### Simultaneous testing

when conducting two tests at the same time, results yield a higher net gain in sensitivity, but a net loss in specificity, compared with doing either test alone.

### Sequential testing

when conducting two tests in a row, results yield a net loss in sensitivity, but a net gain in specificity, compared with doing either test alone.

### Positive predictive value

what proportion of patients who test positive actually have the disease in question. To calculate, divide the number of true positives by the total number who tested positive (true positives and false positives).

### Negative predictive value (PPV)

this result tells us the proportion of people that test negative and do not have the disease. To calculate, divide the number of true negatives by the total number who tested negative (true negatives and false negatives)

### Validity

when applied to screening tests, the ability to distinguish between who has a disease and who does not.

### Reliability

the repeatability of a test with the same exact results. If others do the same exact test and get similar results, the test has high reliability.

### Intrasubject variation

variation between individual subjects taking in consideration the conditions of the test. Ie. Fasting or postprandial glucose testing.

### Intraobserver variation

variation occurs between two or more readings of the same test results by the same observer in which the greater subjective the element being read, the greater the variation.

### Interobserver variation

variation occurs when two examiners derive different results.

### Kappa

expresses the extent to which the observed agreement exceeds that which would be expected by chance alone (numerator) relative to the most that the observers would hope to improve their agreement (denominator)

### The cohort effect

describes variations in the characteristics of an area of study over time among individuals who are defined by some shared temporal experience or common life experience

### PICO

population / intervention / comparison / outcome

### Evidenced based practice

used to improve patient outcomes by combining the best available clinical evidence, patients' values and expectations as well as clinical experiences

### 5 year survival rate

the percentage of people who are alive five years after treatment begins, or they are diagnosed.

### Lead time

apparent lengthening of survival due to earlier diagnosis in the course of disease without any actual prolongation of life

### Life table

is a table which shows, for each diagnosis, what the probability is that a person of that diagnosis will be alive after each year

### Cumulative survival

the proportion who survived from the point they were enrolled in the study, to the end of the interval.

### Median survival time

the length of time that half of the study participants survive

### Relative survival rate

the number of observed survival in people with the disease, divided by the number of expected survival if the disease was absent

### Withdrawals

people whom data is not available for use

### Will Rogers Phenomenon

when the Okies left Oklahoma and moved to California , they raised the average intelligence levels in United States.

### Pathognomonic

a characteristic of a disease that is so distinctive and specific to that disease that a diagnosis can be made based upon it.

### Stage migration phenomenon

occurs when patients are reclassified from one group to another, as a result of improved diagnostics and/or changes in therapy, thereby skewing the results of the study.

### Kaplan- Meier method

a graphic presentation of data that each subjects' exact time of death is indicated and a new interval, and a new row in the life table is started. The # of persons who died at that point is the numerator, and the number alive up to that point (incl. Those who died at that time point) is the denominator (after withdrawals that occurred before that point are subtracted).