A clinical trial is the direct comparison of two or more
treatment modalities in human groups.
- Evidence-based medicine is the integration of current best
evidence with clinical expertise, pathophysiological knowledge,
and patient preferences to make health decisions.
The practice of evidence-based medicine is encouraged because
it may lead to more consistent and objective clinical decisions.
A type I error occurs when a study finds a difference in effectiveness
between the treatments being compared when in fact no difference
A type II error occurs when a study fails to find a difference
in treatment effectiveness between the treatments being compared
when in fact a difference does exist.
- Statistical power is the ability of a study to detect a true
difference between groups being compared.
When treatments are assigned by randomization, probability
alone determines assignment, rather than the personal preferences
of either physicians or patients.
When patients are unaware of their treatment assignment in
a clinical trial, it is referred to as a single-blinded study. In
a double-blinded study, neither the patients nor the treating physicians know
individual treatment assignments.
A ratio of either rates or risks can be used to compare the
outcomes in the experimental and control groups.
- Meta-analysis is a statistical integration of the results
of several independent studies.
A sensitivity analysis can be used to determine whether differences
across studies may be explained by characteristics of the various
An active 13-year-old middle school student complains to her
parents of increasing thirst, frequency of urination, and fatigue
that has persisted for a week. The following morning, the girl and her
parents visit their family pediatrician. While taking the history,
the physician notes the above-mentioned symptoms, as well as a decrease
in the girl’s academic performance over the previous week.
She is consuming more than 3 liters of liquid a day and urinating
approximately eight times during a 24-hour period; at least one
of those times requires her to awaken from sleep. On physical examination,
she is found to be afebrile, with a pulse of 80, which is slightly
elevated for the patient, a normal blood pressure lying and sitting,
and a normal respiratory rate. The pediatrician notes that the girl’s
weight has dropped 2 kg since a visit 3 months earlier. The remainder
of the physical examination is unremarkable.
In the office, the pediatrician performs a urinalysis, which
reveals a normal microscopic examination; the dipstick examination
of the urine is negative for blood, white blood cells, and bilirubin, but
is 4+ positive for glucose and 1+ positive for
ketones. The pediatrician expresses concern to the parents that
the girl may have diabetes mellitus. A complete blood count and
blood chemistries are sent to a local laboratory, and the doctor
arranges for the patient and her parents to see a pediatric endocrinologist
within the hour.
In the endocrinologist’s office, the results of the
blood tests confirm that the girl has a markedly ...