Diagnosing whooping cough can be difficult, because an infected person often appears healthy between coughing fits. A healthcare provider may suspect whooping cough if there has been a recent outbreak in the community, or if symptoms of other respiratory disorders that feature a cough, such as bronchitis or a cold, are not present.

To rule out other diseases, a physician may order:

• Complete blood count. A blood test that provides a basic evaluation of the cellular components in blood. Included are the number of blood cells and platelets, the percentage of each type of white blood cell and hemoglobin content. The size and shape of red blood cells also can be determined.
  
  
• Chest x-rays. These provide a good outline of the heart and major blood vessels. They can usually reveal serious diseases of the lungs.
  
  
• Pulse oximeter. A small probe is placed on the ear or finger to measure the amount of oxygen in the blood. This painless procedure allows physicians to determine blood oxygen levels without drawing blood.