64 PART 2 Examining Tools and Processes

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» ^{Outcome-related: This includes ensuring you are measuring both efficacy}

and safety outcomes on a regular schedule that is documented. You may be

asking the participant to keep records, or they may need to be measured in

person (to obtain laboratory values, X-rays, and other scans, ECGs, and so on).»

» ^{Potential confounding variables: These variables are determined by way of}

what is known about participants’ relationship with the intervention, outcome,

and study eligibility criteria. Typically, potential confounding variables include

basic demographic information such as date of birth, gender, and ethnicity.

Confounders could also be measured with questions posed to the participant

about health behaviors such as tobacco use, exercise patterns, and diet. There

are also questions about medical history, including current conditions, past

hospitalizations, family medical history, and current and past medication use.

Measurements such as height and weight as well as other physical measure-

ments can also be included.

Values that do not change over time, such as birth date and medical history, only

need to be recorded at the beginning of the study. In designs including follow-up

visits, values that change over time are measured multiple times over the duration

of data collection for the study. Depending on the research objectives, these could

include weight, medication use, and test results. Most of this data collection is

scheduled as part of study visits, and but some may be recorded only at unpredict-

able times, if at all (such as adverse events, and withdrawing from the study

before it is completed).

Deciding who is eligible for the study

Because you can’t examine the entire population for whom the intervention you’re

studying is intended, you must select a sample from that population. How you

filter in the right sample for your study is by explicitly defining the criteria a

potential participant has to meet to be eligible to be enrolled and maintained in

the study as a participant.»

» ^{Inclusion criteria are used during the screening process to identify}

potential participants who are members of the population about whom you

want to draw conclusions. A reasonable inclusion criterion for a study of a

lipid-lowering intervention would be, “Participant must have a documented

diagnosis of hyperlipidemia, defined as total cholesterol 200 mg/dL and

LDL

mg/dL

130

^{at screening.”»}

» ^{Exclusion criteria are used to identify potential participants who do not fall in}

the population being studied. They are also used to rule out participation by

individuals who are otherwise in the population being studied but should not