Measuring Health Outcomes Flashcards
Proximal determinants include…
Include individual behaviors
Proximal determinants are viewed as having the most direct effect on health status. Examples include individual behavior such as hand-washing, alcohol and cigarette use), beliefs, attitudes, genetics and biology.
Measuring health status of individuals or populations can be used to
Measuring the health status of individuals or populations provides valuable information that can be used for several purposes including measuring the magnitude of disease, conducting surveillance of a disease in a population, improving clinical decisions, and evaluating the effectiveness of programs.
Health indicators
Indicators are characteristics that can be measured directly or indirectly and can be used to describe health.
Indicators can be qualitative or quantitative and can measure proximal or distal determinants as well as the disease or illness or instead, positive aspects of health such as quality of life.
Composite indicators
Are useful for multi-dimensional concepts that can’t be captured by a single indicator
Indicators can also be indices or composite measures which are formed when individual indicators are compiled into a single index. This is useful for multi-dimensional concepts that can’t be captured by a single indicator
Interval scales have no…
Have no true zero point
Interval scales are quantitative in nature, and do not have a true zero point where there is nothing left of the attribute. One advantage of interval scales is that statistical calculations can be performed.
The main concepts related to quality of measurement are
Validity and reliability
If a scale is incorrectly calibrated and systematically subtracts 10 kg from each weight reading but gives consistent readings, this scale would be
Reliable and invalid
A weight scale that systematically subtracts 10 kg from each respondent’s true weight is reliable because it measures the weight consistently but is not valid because each measurement is 10 kg lower than the true weight.
Internal validity is
The degree of certainty that changes in variables in an experimental study are caused by the treatment or intervention
Internal validity refers to the degree to which we are certain that changes in variables in a study are caused by the treatment or intervention. It refers to how well the study was run, including the appropriateness and rigor of research design, how indicators were measured, what wasn’t measured as well as factors such as selection bias and attrition.
Criterion validity
Criterion validity measures how well one instrument compares against another instrument or a “gold standard” that is known to be close to the truth. To assess criterion validity of a biological or clinical screening test, one would conduct a sensitivity and specificity assessment where the test is compared against a gold standard method of diagnosis.
Sensitivity is
The ability of the test to correctly identify true positives
Sensitivity and specificity assements are an approach to measuring validity and not reliability.
Specificity is
Specificity is defined as the ability of a test to correctly identify those who DO NOT actually have the disease, otherwise known as the true negatives.
A false negative is
Someone who truly has the disease and who tests negative with the test of interest
The negative predictive value
& equation
The negative predictive value (NPV) is the proportion of people who tested negative who actually don’t have the disease
= TN/(TN+FN)
Will the sensitivity and specificity of a test always be consistent, regardless of context/population?
No, it will vary in different settings and populations
Reliability refers to
Reliability refers to the consistency of a measure, or the degree of stability exhibited when a measure is repeated under identical conditions.
Test-retest reliability assesses
Variation in measurements taken by a single person or instrument under the same conditions
Inter-observer reliability
Is a measure of agreement between two or more observers measuring the same concept
An individual or population’s overall level of health is an example of
Health status
Health status is an individual or population’s overall level of health.
Public health concerns
The overall health of groups and the distribution of health within the group
Which of the following is true regarding mortality?
Mortality rate is not a useful indicator.
Neonatal mortality rate is the number of deaths of liveborn children under 28 days of age per 100,000 live births per year.
The first known mortality data was collected by John Snow in London.
Neonatal mortality rate is the number of deaths of liveborn children under 28 days of age per 1,000 live births per year.
The crude mortality rate takes into account age.
Neonatal mortality rate is the number of deaths of liveborn children under 28 days of age per 1,000 live births per year.
Traditionally mortality has been the most important indicator of the health status of a population. The first known systematic collection of mortality data was developed by John Graunt, and crude mortality rate does not take into account age. Neonatal mortality rate is typically expressed per 1,000 live births
What is a key fact to remember about incidence?
Incidence focuses only on new cases of a disease that occur within a certain period of time
Incidence refers to the number of new cases of a disease that occur during a specified period of time in a population at risk for developing the disease. The denominator, therefore, only includes people who have the potential to develop the disease in the future.
In a population of 5,000,000 people at a given time 33,000 people have Disease X. The prevalence is
0.66%
The prevalence is calculated by dividing 33,000 by 5,000,000 and multiplying by 100. This yields a prevalence of 0.66%.
Disease Y occurred at a rate of 149/1000 per year in a population of women aged 15-49 who did not previously have Disease Y. This is an example of..
A case fatality rate An incidence rate A crude disease rate A point prevalence rate A prevalence rate
An incidence rate
The information describes the rate of occurance of a disease within a population who is at risk for developing the disease in the future and thus is an incidence rate.
In City A, which has a population of 100,000, there are 200 new cases of tuberculosis reported between January 1, 1998 and December 31, 1998. What is the annual incidence of tuberculosis for this population? Assume that the number of existing cases on January 1 1998 was negligible.
2 per 1,000 per year
There are 200 new cases per year in a population of 100,000. This is equivalent to 2 cases per 1,000 per year.
Which of the following is a true statement?
The risk of maternal death is most often measured by the neonatal mortality rate
The severity of a disease is measured via incidence and prevalence
Neonatal mortality rate is usually higher than infant mortality rate
A disease’s burden relies on knowing only the proportion of people who have that disease in the population
All of the statements are false. Burden of diseases in a population depends on their frequency (incidence or prevalence), severity (mortality and extent of serious morbidity), consequences (health, social, economic) and type of people affected (gender, age). Risk of maternal death is most often assessed by the maternal mortality ratio. Neonatal mortality, which is defined as the probability of dying within the first month of life, is always less than the infant mortality rate, which is defined as the probability of dying within the first year of life.
Prevalence includes:
Existing cases present at a single point in time
Prevalence is the number of affected individuals in a population at a specific time divided by the number of persons in a population at that time. Prevalence is essentially a snapshot of the proportion of the population who has the disease at a given moment in time.
In Town B, the prevalence of disease Z is 4.6%, and the average duration of the disease is 4 years. What is the incidence rate of the disease?
11.5 per 1,000
In a steady state where rates are not changing and in-migration equals out-migration, prevalence and incidence can be related by the following equation: prevalence = incidence x duration of disease. To calculate incidence rate with the given information, 0.046 is divided by 4 and then multiplied by 1,000 to give a rate per 1,000.
If the prevalence of disease J has been roughly constant for the last 10 years, and assuming no other changes, what would be the impact on prevalence of a program that reduces incidence of disease J?
It would decrease prevalence of the disease
In a steady state where prevalence is stable, a decrease in incidence of a disease would mean that there are fewer new cases of the disease within a population. This would ultimately lead to a reduction in the prevalence over time.
Which of these is a distal determinant of health?
Individual behaviors
Diet
Environmental Factors
Tobacco use
Environmental factors
Distal determinants have a more indirect effect on a person’s health and tend to be background factors in the sociocultural and environmental context that can predispose people to greater or lower health risks. Examples include cultural factors, education level and the physical environment.
DALYs?
DALYs (Disability Adjusted Life Year) assess the number of years lost due to ill health, disability or early death. 1 DALY is equivalent to 1 year of healthy life lost.
QALYs
QALYs (Quality Adjusted Life Year), on the other hand, focus on the quality and quantity of life lived.
population attributable fraction
Population attributable fraction assesses the percent reduction in incidence rate of a disease that would occur if a certain risk factor were to be eliminated. The population attributable fraction of type 2 diabetes due to physical inactivity is the proportion of incident cases that would be reduced if physical inactivity was eliminated from the population
Which of the following statements is true regarding questionnaires?
Instruments exist but not all have been validated for use in every setting
Instruments exist and can be used in any setting
Questionnaires must always be created from scratch
A wide variety of questionnaires for health research exist and are available for use. However, not all of these tools have been validated for every context, so it is important to review evidence for the existing tools before making a decision.
Which of the following statements is true?
Vital signs are measurements that are invasive.
Interview guides are used for collecting qualitative data
The Patient Health Questionnaire (PHQ) is used for assessing overall quality of life
Field notes include questions and responses the enumerator can either check off or fill in
Interview guides are used for collecting qualitative data
Field Notes are the least structured tool for observational data collection and do not include any preset questions or responses. The PHQ is a tool for assessing depression. Vital signs are a non-invasive measurement.
Anthropometry
Anthropometry is the measurement of the human body. Anthropometric measures include height, weight, mid-upper arm circumference (MUAC), head circumference and waist and hip circumference. In anthropometry, inter-observer variability can be an issue.
MUAC stands for
Mid upper arm circumference
which is measured to assess malnutrition.
Which of the following statements is true about dried blood spots?
Usually 5 to 6 spots are collected per person
They involve collecting finger prick blood on a glass slide
Most clinical assays that use venous blood can be performed with dried blood spots
They require cold chain
Usually 5 to 6 spots are collected per person
Dried blood spots do not require cold chain or glass slides. They involve depositing drops of finger prick blood onto a special type of filter paper card and allowing it to air dry. Usually 5 to 6 drops are collected per person, however the number and range of assays available for dried blood spots is limited.
Point of care tests
Are tests that give rapid results on the spot and can be performed by staff with minimal training.
Health
Health is a complex multi-dimensional concept. It is usually measured in terms of the absence of physical pain, physical disability, or a condition that could lead to death or disability. As well as in terms of the presence of emotional and mental well-being, and adequate social functioning.
proximal determinants
viewed as having the most direct effect on health status. Examples include individual behavior such as hand-washing, alcohol and cigarette use, beliefs, attitudes, genetics, and biology.
