Rather than relying on a single test, it's recommended to carefully monitor the patient's lung function over time. Logging PEF measurements over two weeks achieves a much more nuanced picture of a patient's respiratory health. Why is this important? If a patient happens to be experiencing a period where their condition is stable and symptoms are minimal when a single test is carried out – the results may miss signs of asthma, even if you suffer from the disease.
"To truly understand asthma, we must consider lung function over time, not just at a specific moment." - Dr. George Grantson
🌬️What is PEF measurement?
PEF stands for "peak expiratory flow" and describes how fast someone can exhale. AsthmaTuner's spirometer works both as a lung function meter and a PEF meter, meaning that healthcare professionals don't need to prescribe a separate meter. Patients also don't need to manually note their results – everything is saved automatically.
🕖 When should the test be performed?
According to the updated guidelines, patients should carry out two measurements daily: one in the morning and one in the evening. If symptoms arise, additional measurements are recommended. The aim is to identify any sudden changes in lung function.
📏How should measurements be calculated?
According to GINA's guidelines, daily variability in PEF is calculated by subtracting the day's lowest PEF value from the highest, and then dividing the result by the average of these two values. This is done on average over a week. For each PEF measurement, you should use the highest of three readings.
🔍How should the values be interpreted?
If the daily variability exceeds 10% for adults or 13% for children, it could be an indication of asthma.
In AsthmaTuner, both daily variability and a weekly average are presented. If this weekly average of daily variability exceeds 10% for adults or 13% for children, it may indicate asthma. The example in the image thus suggests asthma for adults.
Summary
We’re seeing a shift in the way asthma is diagnosed. A regular lung function measurement (spirometry) cannot rule out asthma, as asthma is a variable disease where lung function can vary over time. This means that if spirometry results are normal but symptoms suggest asthma, further investigation is required. New guidelines tell us that daily PEF measurements can be used, where daily variability exceeding 10% for adults or 13% for children indicates asthma.
