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

5 Click here Medicare Health Outcomes Survey

6 Click Here os/download/HOS_2006_Survey.pdf

7 Medicare HOS

8 General Practice Research Database United Kingdom

9 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

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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

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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.

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20 Data and Documentation – NHANES

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

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30 Positively Skewed

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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 < ) 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 1 st and 4 th Quartiles with respect to Chest Pain

48 Cardiac Symptoms Questionnaire and CRP Compare 1 st and 4 th 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