How Is The Diagnosis Of Asthma Established?

Gemma’s comment: In my 60s, I had, at different times, two primary care physicians: one whose specialty was gastrointestinal medicine, the other whose specialty was cardiology. In routine interviews, they both asked if I coughed on a daily basis, and of course, I said “yes.” Yet neither one suggested that I should see a pulmonologist, and I was not surprised, since I was used to coughing and thought of it as normal.

My asthma was diagnosed only when I turned up for a routine visit in the cardiologist’s office with a bad cold and a wheeze. In the light of my experience, it’s easy for me to believe that asthma is underdiagnosed. 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 text-book, 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 his-tory 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 his-tory. 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. As described in Question 16, 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 some-times 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 deter-mining if asthma is the correct diagnosis in spite of the spirometry results.

Tools for Diagnosing Asthma


Physical examination

Pulmonary function testing:

  • Spirometry
  • Peak expiratory flow
  • Challenge testing
  • Arterial blood gas

Blood tests

Radiographic tests:

  • Chest X-ray
  • Chest CT scan