PHC215

By Dr. Khaled Ouanes Ph.D.

E-mail: k.ouanes@seu.edu.sa

Twitter: @khaled_ouanes

INTRODUCTION TO

HEALTHCARE RESEARCH

METHODS

Secondary Studies:

Existing Data Sets

Overview

Secondary analysis: the researcher conducting the statistical analysis has not had

(and does not have) any contact with the

individuals whose data are being examined.

Sources: publicly available individual-level or population-level data

privately held survey data

clinical records

Publicly Available Data

Sharing data is a cost-efficient way to extract as much information as possible out of data sets.

For example, the U.S. Centers for Disease Control and Prevention (CDC) provides, on its website, data from several nationwide cross-sectional studies: National Health and Nutrition Examination Survey (NHANES)

National Health Interview Survey (NHIS)

Behavioral Risk Factor Surveillance System (BRFSS)

Advantages

Researchers may be able to download an entire

cleaned data set (and supporting documentation)

immediately and at no cost directly from the

website of the sponsoring organization.

Secondary analysis is an excellent option for

researchers with strong statistical skills but limited

time and/or data collection resources.

Limitations

The analyst is limited to exploring only the topics included in the original survey.

The analyst has to trust that the data were collected using valid and standardized methods.

It may be difficult to find someone who can answer questions about the data collection process.

There is a risk of duplicating the analysis that someone else has done or is doing.

Private Data

Individual researchers and research teams, such as

those at universities or university hospitals, may have

data available that have not yet been analyzed.

The original researcher – the one who collected the

data – may be open to a new researcher taking the

lead on analyzing that portion of the data set and

writing up the results for possible publication.

Limitation: Patient records are often incomplete.

Clinical Records

Clinical records are a common source of data for

case series.

Individuals working in clinical settings commonly

have access to patient records for research

purposes, provided that the research project

receives all required approvals and will not violate

any law (such as HIPAA) or policy.

Ethics Committee Review

Additional approval by an ethics committee at

the institution where the secondary analysis will be

conducted is usually not required for anonymized

publicly available data.

Secondary analysis of private data or hospital

records almost always requires review by a

research ethics committee.

Tertiary Studies:Systematic Reviews &

Meta-Analyses

Overview

A systematic review is the careful compilation and

summary of all publications relevant to a particular

research topic.

A meta-analysis creates a summary statistic (a pooled

statistic) for the results of systematically identified

articles.

Systematic Review Process

Search Strategy

After identifying a well-defined study question, the

next critical step in a systematic review or meta-

analysis is to select appropriate databases, search

terms, and search limiters.

Once a system for identifying eligible articles is in

place, abstract databases are systematically

searched for articles that meet all the inclusion

criteria.

Systematic Search

Strategy & Counts

to Report

Data Extraction

Once all eligible articles are identified, the content of

these articles is extracted into data extraction tables

that list descriptive characteristics like:

The study location and study years

The study design

The study population and sample size

The key findings of interest

The strengths and limitations of the study

Data Extraction

A data extraction table allows for easy compilation

and comparison of observations relevant to the

study question.

Studies that find no statistically significant results for

an item of interest are just as valuable as those that

find a significant association.

Publication bias occurs when articles with

statistically significant results are more likely to be

published that those with null results.

Meta-Analysis

A meta-analysis pools the results of several studies

identified during a systematic review to create one

summary statistic.

Only similar statistics from similar studies can be

pooled.

Before pooling the data, the researcher must show

that the results of the studies are comparable.

A specialized computer software program can be

used to estimate the value of the pooled statistic and

its confidence interval.

The contribution of each study to the pooled estimate

is usually weighted based on the sample size of the

included studies.

The contributing studies and the summary measure are

often displayed using a forest plot.

Meta-Analysis

Example of a Forest Plot graphical

display

Threats to the validity of a meta-analysis:

Poor quality of included studies: The selection criteria

used during the systematic review process can

eliminate any studies of questionable validity.

Publication bias: The possibility of publication bias can

be examined using a funnel plot.

Meta-Analysis

Example of a Funnel Plot graphical

display

PHC215

By Dr. Khaled Ouanes Ph.D.

E-mail: k.ouanes@seu.edu.sa

Twitter: @khaled_ouanes

HEALTHCARE RESEARCH METHODS

Based on the textbook of introduction to health research methods – K.H. Jacobsen