How is the diagnosis of asthma established?

The diagnosis of asthma is often straightforward, but
can also be time consuming and elusive. Asthma can
manifest differently in different individuals because of
its waxing and waning nature, as well as its variability.
A physician evaluating a patient with a typical, or textbook,
presentation will likely be able to diagnose asthma
correctly at the first visit. A patient with variant or
atypical symptoms may require repeat visits or specialized
diagnostic testing to confirm the suspected diagnosis
of asthma. More severe forms of asthma are usually
easier to pinpoint and diagnose accurately. Consider
some examples in each category. A previously healthy,
nonsmoking young adult who reports an episodic history
of intermittent wheezing, cough, chest discomfort,
and breathlessness with exposure to cold winter air is
describing a history typical of asthma. The college student
who sees the doctor because of a nagging cough and
who is concerned about chronic or recurrent bronchitis
and colds, might actually be asthmatic. Similarly, the
teenager who gets “really winded” playing racquetball,
and then gets used to coughing for a few hours after
each match, could certainly have asthma as well.

Asthma can be confidently diagnosed when specific
symptoms, physical examination findings, and specialized
lung test results are present. The first step in the evaluation
of suspected asthma is a complete detailed medical
history, during which the doctor and the patient meet face
to face for an in-depth conversation and exchange of
information. The patient will describe what symptoms he
or she is experiencing, and the physician will ask a series
of directed questions regarding lung health, followed by
more general health inquiries. In this fashion, the physician
will obtain information not only about the patient’s
specific pulmonary symptoms, but also about the presence
or absence of allergies, and other medical or surgical
conditions. Other important background information
derives from review of the patient’s medication history,
along with his or her travel, occupational, and social history.
Some questions may at first sound intrusive, but
should nonetheless be answered truthfully.When I ask a
patient if there is wall-to-wall carpeting in the bedroom,
or who does the vacuuming, for example, I am far from
interested in discussing domestic decorating or cleaning
arrangements. Rather, I am gathering facts to help me
decide whether an allergic response to the home environment
is a possibility. Similarly, when I ask, “Is anyone else
at home coughing, too?” or “Is anyone at home a smoker?”
I am searching for clues to help me hone in on the
correct diagnosis. All conversations between my patients
and me are entirely confidential; truthfulness between us
is an important part of the successful doctor–patient
relationship. Just as I would never think of telling a patient
an untruth, so, too, do I count on my patients to provide
me with an accurate description or history.
After history taking comes the physical exam. Most lung
specialists will perform a directed physical, with special
emphasis on the upper respiratory tract (nose, throat,
sinuses), lungs, and the skin. One can expect measurement
of vital signs, including blood pressure, respiratory
rate, pulse, and if necessary, temperature. Inspection, percussion,
and auscultation are techniques that examine the
lungs. Inspection refers to a visual look. The specialist will
check whether both lungs move in and out with each
breath, for example. Percussion involves gently tapping
on the chest, listening for clues as to whether or not the
lungs are full of air. If the lungs are full of air, the tapping
will sound resonant. If the lungs are not entirely filled
with air, then the tapping will give rise to a dull sound.
Auscultation requires a stethoscope.
The examiner will ask the patient to inhale
and exhale deeply and regularly during auscultation. The
presence or absence of wheezing is especially significant.
After the history and the physical exam are completed,
the doctor will begin to generate a list of diagnostic possibilities,
called the differential diagnosis.
The doctor’s clinical impression rates the
possible diagnoses in order of likelihood. It may sometimes
be obvious to the physician that asthma is present.
A pulmonary function test called spirometry (obtained
before and after inhalation of a bronchodilator medicine)
is indicated in order to confirm the suspected asthma
diagnosis. If spirometry is not confirmatory and if asthma
remains high on the list of possible explanations for
a patient’s symptoms, then additional diagnostic testing
is often obtained . The additional testing is helpful in excluding
alternative diagnoses and in determining
if asthma is the correct diagnosis in spite of the
spirometry results.