clinical investigation and outcomes research research using existing databases

1

Clinical Investigation and Outcomes Research

Research Using Existing Databases

Marcia A. Testa, MPH, PhD

Department of Biostatistics

Harvard School of Public Health

2

Accessing and Using Existing Clinical Research and Health

Outcomes Databases• A large number of existing databases are available

to clinical and health outcomes researchers– public access – limited or restricted-use data

• Public access data bases require no prior approval or fee and most often can be downloaded from the internet

• Limited and/or restricted use databases require approval application, fee or both

3

Sources of Public Access Research Databases

• Common sponsors of public access databases are in the United States– Center for Disease Control and Prevention (CDC)– National Institutes of Health– Bureau of the Census– Agency for Health Care Research and Quality– Health and Human Services Agencies

• World Health Organization• General Practice Research Database of the UK

4

How Do I Get the Data?

• Before downloading and analyzing data you must spend considerable time learning about the data and formulating your research hypothesis

• Sampling schemes, data collection methods, sampling weights and appropriate statistical routines should all be considered

• Most databases and documentation can be ordered on tapes (older data), CD’s or by downloading the data from the internet

• However, the data is not “READY” straight off the shelf

5Click here

Medicare Health Outcomes Survey

6

Click Here

http://www.hosonline.org/surveys/hos/download/HOS_2006_Survey.pdf

7

Medicare HOShttp://www.hosonline.org/surveys/hos/hosdata.aspx

8http://www.gprd.com/home/default.asp

General Practice Research Database United Kingdom

9http://www.cdc.gov/nchs/

CDC National Center for

Health Statistics

10

CDC National Center for

Health Statistics

11

CDC National Center for

Health Statistics

12

NCHS Research Data Center

13

14

NHANES

• The National Health and Nutrition Examination Survey (NHANES) is a program of studies designed to assess the health and nutritional status of adults and children in the United States.

• The survey is unique in that it combines interviews and physical examinations.

• Began in 1960’s and the diseases studied include:• Anemia , Cardiovascular disease, Diabetes, Environmental exposures,

Eye diseases, Hearing loss, Infectious diseases, Kidney disease, Nutrition, Obesity, Oral health, Osteoporosis, Physical fitness and physical functioning, Reproductive history and sexual behavior, Respiratory disease (asthma, chronic bronchitis, emphysema), Sexually transmitted diseases, Vision

15

As Example of Research using the NHANES Database

Original Research Problem

April, 2010

16

•http://www.cdc.gov/nchs/tutorials/NHANES/index_current.htm

17

By clicking on each on of the links you will be instructed how to navigate and prepare your dataset.

18

In the “Data Structure and Contents Module” you will be shown the general layout of the data files.

19

20

Data and Documentation – NHANES 2007 - 2008

21

Laboratory Files

22

Questionnaire Files

23

Demography File

24

CRP, HbA1c, Cardiac Symptoms

• Investigate the relationships between– C Reactive Protein (CRP)– HbA1c– Symptoms of Heart Disease (Pain in

Chest) – Demographic Characteristics of age and

gender

25

CRP, HbA1c, Cardiac Symptoms

• Is higher HbA1c associated with higher CRP levels?– in males– In females

• Are cardiac self-reported symptoms (e.g., chest pain) associated with higher CRP levels?

26

Download Files

27

Merge Files into Statistical Package (e.g. SPSS)

28

Descriptive Statistics

• Merge four files– Demography– CRP– HbA1c– Cardiac Symptoms Questionnaire

29

30

Positively Skewed

31

32

Glycohemoglobin %

More Normally Distributed

33

Are CRP and HbA1c Correlated?

• The higher CRP, the higher HbA1c

34

CRP Quartiles

Divide sample into quartiles based upon CRP levels

CRP Quartiles

35

HbA1c by CRP Quartiles

CRP Quartiles

36

Is there a difference between Males and Females?

37

Is there a difference between Males and Females?

• Females have a higher CRP (p < 0.0001) • HbA1c levels are slightly lower (p = 0.061)

38

Is there a difference between Males and Females after controlling for age?

• Age is slightly higher in females – so control for age in analysis

39

Is there a difference in CRP between Males and Females after controlling for age?

40

Is there a difference between Males and Females after controlling for age?

41

Cardiac Symptoms Questionnaire and CRP

42

Cardiac Symptoms Questionnaire and CRP

Significant symptom and (gender X symptom) interaction

43

Cardiac Symptoms Questionnaire and CRP

44

Cardiac Symptoms Questionnaire and CRP

Interaction

45

Investigate Further

46

Cardiac Symptoms Questionnaire and CRP

47

Cardiac Symptoms Questionnaire and CRP

Compare 1st and 4th Quartiles with respect to Chest Pain

48

Cardiac Symptoms Questionnaire and CRP

Compare 1st and 4th Quartiles with respect to Chest Pain

49

Cardiac Symptoms Questionnaire and CRP

50

Cardiac Symptoms Questionnaire and CRP

51

Summary

• Clinical research using existing databases is an excellent way to practice your research skills, while at the same time testing original hypotheses – potentially to be published

• Data quality is excellent, data is either at no cost or low cost and is immediately available