Diagnosing Asthma

A diagnosis of asthma is based on a person’s:

Medical history; information such as what signs and symptoms of asthma have they had
Family medical history; has anyone they are related to had asthma or related conditions such as occur with those who are atopic
Physical examination and testing.

Diagnostic Tests

There is no specific test that can tell if a person has asthma, however there are tests that can help in the diagnosis when the results are considered along with the medical and family history and physical exam

Lung function tests Pulmonary function tests (PFTs)
Spirometry; measures how much air the lungs are able to breathe in and how much air they breathe out and how fast a person can exhale.
Bronchoprovocation test; in this test the airways (bronchi and bronchioles) are provoked (to try and make something happen) into having a bronchospasm (make the airways constrict) this is to see how sensitive they are. Some of the things done to provoke a bronchospasm are making the person exercise, breathing cold air that gets colder, or breathing in a special chemical called methacholine. The results of bronchoprovocation are checked using spirometry.

Differential diagnoses change | change source

Differential diagnoses are different medical disorders which may cause the same symptoms. Before a doctor makes a final diagnosis, which means they are sure of what medical disorder is causing the problem, they think of what other medical conditions have the same or almost the same symptoms, and make sure it’s not one of them.

Common symptoms and signs include:

  • Wheezing
  • Coughing
  • Breathing difficulty
  • Tightness in the chest
  • Worsening symptoms at night
  • Worsening symptoms due to cold air
  • Symptoms while exercising
  • Symptoms after exposure to allergens

It is also wise to make note of health conditions that can interfere with asthma management such as runny nose, sinus infections, acid reflux disease, psychological stress, and sleep apnea.

It is often somewhat harder to diagnose young children who may develop their first asthma symptoms before age 5. Symptoms are likely to be confused with those of other childhood conditions, but young children with wheezing episodes during colds or respiratory infections are likely to develop asthma after 6 years of age.

Physical ExamA child using a peak flow meter(PFM) which measures how well air moves out ( the peak expiratory flow, or “PEF”) of a person’s lungs when they breath out (exhale).

 

 Physical Exam

A physical examination will generally focus on the upper respiratory tract, chest, and skin. A doctor will use a stethoscope to listen for signs of asthma in your lungs as you breathe. The high-pitched whistling sound while you exhale – or wheezing – is a key sign of both an obstructed airway and asthma.

Physicians will also check for a runny nose, swollen nasal passages, and nasal polyps. Skin will be examined for conditions such as eczema and hives, which have been linked to asthma.

Physical symptoms are not always present in asthma sufferers, and it is possible to have asthma without presenting any physical maladies during an examination.

Asthma Tests

Lung function tests, or pulmonary function tests, are the third component of an asthma diagnosis. To measure how much air you breathe in and out and how fast you can blow air out, physicians administer a spirometry test.

Spirometry is a noninvasive test that requires you to take deep breaths and forcefully exhale into a hose connected to a machine called a spirometer. The spirometer then displays two key measurements:

Forced vital capacity (FVC) – the maximum amount of air one can inhale and exhale
Forced expiratory volume (FEV-1) – the maximum amount of air exhaled in one second

The measurements are compared against standards developed for a person’s age, and measurements below normal may indicate obstructed airways.

It is common for a doctor to administer a bronchodilator drug to open air passages before retesting with the spirometer. If results improve after the drug, there is a higher likelihood of receiving an asthma diagnosis.

Children younger than 5 years of age are difficult to test using spirometry, so asthma diagnoses will rely mostly on symptoms, medical histories, and other parts of the physical examination. It is common for doctors to prescribe asthma medicines for 4 to 6 weeks to see how a young child responds.

 

Other Tests

A “Challenge Test” (or bronchoprovocation test) is when a physician administers an airway-constricting substance (or something as simple as cold air) to deliberately trigger airway obstruction and asthma symptoms. Similarly, a challenge test for exercise-induced asthma would consist of vigorous exercise to trigger symptoms. A spirometry test is then administered, and if measurements are still normal, an asthma diagnosis is unlikely.

Physicians use allergy tests to identify substances that may be causing or worsening asthma. These tests cannot be used to diagnose asthma, but they can be used to understand the nature of asthma symptoms.

Doctors may also test for another disease with similar symptoms as asthma, such as reflux disease, heartburn, hay fever, sinusitis, sleep apnea, chronic obstructive pulmonary disease (COPD), airway tumors, airway obstruction, bronchitis, lung infection (pneumonia), blood clot in the lung (pulmonary embolism), congestive heart failure, vocal cord dysfunction, and viral lower respiratory tract infection.

Tests may be administered for these ailments such as chest x-rays, EKGs (electrocardiograms), complete blood counts, CT (computerized tomography) scans of the lungs, gastroesophageal reflux assessment, and sputum induction and examination.

A new test using exhaled nitric oxide is being evaluated since physicians are looking for a test that is more accurate than spirometry. Higher levels of nitric oxide are linked to higher degrees of asthma severity. The current drawback lies in the high cost of the test and the specialized equipment required to measure this chemical marker.

An asthma specialist can usually be avoided as most primary care physicians are capable of diagnosing asthma. An asthma specialist may be necessary, however, if you need special asthma tests or have had a life-threatening asthma attack in the past. In addition, specialists can be of use if you need more than one kind of medicine or higher doses of medicine in order to control your asthma, if you have overall difficulty controlling asthma, or if you will be receiving allergy treatments.