1. Asthma diagnosis considers symptoms and variable airflow

The 2026 GINA Summary Guide describes diagnosis as confirming both a pattern of variable respiratory symptoms and variable expiratory airflow. Wheeze, shortness of breath, chest tightness, and cough can have other causes, so symptoms alone do not establish asthma. Spirometry is an important objective test; where possible, documenting variability during symptoms or before treatment can help confirm the diagnosis.

2. FEV1/FVC and bronchodilator response are different measurements

An FEV1/FVC ratio below 70% is not a fixed asthma criterion for every age. Interpret the ratio using age-appropriate lower limits of normal and testing standards. Under GINA 2026, a bronchodilator response supporting variable airflow in adults is an increase in FEV1 or FVC of at least 12% and at least 200 mL from baseline. For ages 6–17, the criterion is an FEV1 increase of at least 12% of predicted. Preparation, medication withholding, test quality, and symptoms affect interpretation; one number alone is not a diagnosis.

Example: On an adult report, check that both “FEV1 +12%” and “+200 mL” are met. The FEV1/FVC ratio and the change in FEV1 after a bronchodilator are different measures; do not substitute one for the other. A result at a threshold still needs clinical interpretation alongside symptoms.

3. Keep PEF separate from FEV1 and check the period and method

Peak expiratory flow (PEF) can be used when spirometry is unavailable, but GINA considers it less reliable. PEF is the highest flow from a handheld meter; FEV1 is the volume exhaled in the first second measured by spirometry. Even when both are shown as a percentage, they are not interchangeable.

GINA 2026 defines excessive average daily PEF variability from morning and evening readings over two weeks as above 10% for adults and above 13% for ages 6–17. This is not a threshold for comparing one morning and evening reading on a single day. AAAAI’s peak-flow guide advises using the same meter, taking three readings each time, recording the highest, and comparing readings with a personal best. Share the record and symptoms with a clinician.

4. Use a written action plan instead of changing medicines on your own

The U.S. NHLBI guide to asthma action plans recommends developing a written plan with a health professional. It can identify worsening signs, what to do in each zone, when to use prescribed medicines, and when to contact a clinician or seek emergency care. Follow your own plan; do not borrow another person’s medicine or invent a dose change.

Practical example: Match current symptoms or your personal PEF reading to the zone in your plan, then follow the listed next step and contact instructions. If breathing is extremely difficult, lips turn blue, or consciousness is impaired, seek emergency help immediately under the plan. In the United States, call 911; in Japan, call 119 according to the Fire and Disaster Management Agency; in Korea, call 119 according to the National Fire Agency. Elsewhere use the local emergency number. Clinicians determine diagnosis and treatment for the person’s age and condition; do not self-diagnose or change medicine from a GINA threshold alone.

Sources: GINA 2026 Summary Guide · NHLBI — Asthma Treatment and Action Plan · AAAAI — Peak Flow Meter