Asthma : Diagnosis

Asthma which is a hyper-responsive state of airways causing constriction and mucous secretion making breathing difficult is usually a clinical diagnosis.

Clinical diagnosis includes:

  • history of the patient
  • family history of allergies and asthma
  • symptoms elaboration: exact duration and timing of symptoms
  • physical examination: to look for signs of allergy- skin dryness, eyes
  • examination of chest- air entry, added sounds like wheeze.
  • objective parameter: lung function test
  • test for allergens
  • complete blood count which may demonstrate eosinophilia

Lung function test:

There are two means to measure the lung function

  1. spirometery
  2. PEFR(Peak Expiratory Flow Rate)


source: wikipedia

The patient is told to blow through an instrument continuously for one breath after taking a deep breath and the vital parameters of the lung are calculated by the machine.  These parameters objectify whether the person has a restriction or obstruction in his airways. We can also measure the reversibility by doing a post bronchodialator test and if there is reversibility of 20% , diagnosis of asthma is confirmed.

Spiromtery also helps in monitoring the treatment. Spirometry is always not possible for children and to make a diagnosis in them we do PEFR.




PEFR( Peak Expiratory Flow Rate):

source: wikipedia


PEFR measures the the maximum a pateint can exhale through this instrument in one breath. The child is made to blow out 3 times and best of three is taken and it is compared to his expected PEFR, which depends on the height of the person.

This method is more easy for a child to perform and can also be used by parents for home monitoring of the treatment, as it does not any expertise.


Besides the above mentioned two objective parameters may not be useful in children less than 5 years of age. In these children clinical history and examination is relied upon and also trial of bronchodialators to see response of treatment.

Most of these children do not end up becoming asthmatics as the airways enlarge with age but some may become, hence, a constant follow up is required.



Dr. Mukesh Joshi
Chest Physician