Question

Please review each of the following studies to identify the type of study design and address each of the following criteria per a study:

1. Unit of observation (individual or group)

2. Initial classification of subjects (disease or exposure status)

3. Disease(s)/Outcome(s)

4. Exposure(s)

5. Directionality of exposure measurement (RF(Exp)->D or D->RF(Exp))

RF = Risk Factor

Exp = Exposure

D = Disease

6. Number of observations (# times collected data from subject) (1 or >1)

7. Definition of controls (if applicable)

8. Prospective, retrospective, or concurrent?

9. Type of study design

10. Measures of association you would be able to calculate

A. Investigators identified 50 children who were recently diagnosed with asthma from an outpatient pediatric clinic along with another group of 50 similarly aged children without asthma. Investigators interviewed the mother of each child in order to determine household exposure characteristics that may be of interest such as parental smoking and bug/pest problems in the house.

B. Factory workers in one particular plant are suspected of being at higher risk for lung disease due to asbestos exposure. A random sample of factory employees, who do not have lung disease, is recruited for a study. Asbestos exposure is recorded and the rate of lung disease is compared in office workers not exposed to asbestos and those workers who directly come in contact with asbestos particles. These factory workers are followed for lung disease development for 20 years.

C. One study is being conducted to evaluate two treatments for panic disorder. Study participants are randomized to receive either exposure therapy alone or a combined exposure therapy with the prescription of a low-dose SSRI medication. Subjects are followed for 8 months to determine any differences in quality of life and severity of panic disorder.

D. A study examines the death rates from cervical cancer in each of the 50 US states in relation to the average percentage of women in each state undergoing annual PAP smear screening

Answer 1

a)     1) unit of observation – individual

2) classification of subjects – children with asthma , children without asthma

3) disease – asthma

4)exposure – household exposure like parental smoking and bug/pest problems in house.

5)directionality of exposure measurement

Asthma ->Risk factor (parental smoking and bug/pest problems in house)

6) number of observations from one subject – 1

7) definition of controls-

Removing bug/pest in house & making it clean

Maintaining good health that is being non smokers

8) retrospective – based on past observations ( common for case control studies)

9) type of study design - case control studies ( because it studies about subjects are selected by whether or not they have a disease)

10) measure of association -

Odds ratio = A*D / B*C

exposure	asthma
	yes	no
yes	a	b
no	c	d

b)

1) unit of observation – individual

2) classification of subjects- office workers not exposed to asbestos exposure , workers who directly come in contact with asbestos exposure

3) disease- lung disease

4)exposure- asbestos exposure

5)directionality of exposure measurement-

Risk factor(asbestos exposure) <- lung disease

6) number of observations from one subject- greater than 1

7) definition of controls- making safeguards for workers who directly come in contact with asbestos exposure.

8) prospective- based on future prediction (workers are followed for lung disease development for20 years)

9) type of study design – cohort study ( subject chosen based on having and not having a exposure)

10) measure of association- relative risk

esposure	Lung disease
	yes	no
yes	a	b
no	c	d

Relative risk = (A/A+B)/(C/C+D)

c)     

1) unit of observation-individual

2) classification of subjects- exposure therapy alone , combined exposure therapy with the prescription of low-dose SSRI medication

3) disease- panic disorder

6) number of observations from one subject- more than one

8) prospective ( subjects are followed for 8 months to determine any difference in their quality of life andseverity of panic disorder)

9) type of study design- experimental study- randomized controlled trials ( to test the effectiveness of two treatment, the participants are selected randomly).

10) measure of association- measure the relative risk of disease between the treatment groups.