Optimal Timing for Accurate Asthma Diagnosis

A recent study published in Thorax has shown that a routine lung function test used to diagnose asthma is more accurate when performed in the morning. The research highlights significant variations in the test's effectiveness based on the time of day and the season, indicating that factors such as circadian rhythms and environmental conditions may influence lung function measurements.

Understanding Asthma Diagnosis

Asthma is a prevalent respiratory condition affecting approximately 6.5% of individuals over six years of age in the UK. Characterized by symptoms such as wheezing and shortness of breath, asthma can lead to serious health complications if not properly managed. Common treatment options include inhalers and nebulizers that deliver medication directly to the lungs.

During an asthma diagnosis, patients typically undergo a spirometry test. This test involves inhaling deeply and exhaling forcefully into a device that measures lung capacity. The test may be followed by the administration of salbutamol, a bronchodilator that relaxes airway muscles. A positive result indicates the presence of asthma by showing an improvement in lung function post-treatment.

Research Findings

Utilizing real-world data from 1,600 patients collected by the Victor Phillip Dahdaleh Heart and Lung Research Institute and Royal Papworth Hospital NHS Foundation Trust, researchers observed the following:

• The likelihood of a positive test result decreases by 8% for each hour post 8:30 AM.
• Patients tested in autumn exhibited a 33% lower chance of a positive result compared to those tested in winter.

Table 1: Impact of Timing on Asthma Test Reliability

Seasonal Effects on Test Outcomes

Dr. Akhilesh Jha, a Medical Research Council Clinician Scientist, noted that natural rhythms can significantly cause variations in test outcomes. Circadian rhythms influence hormone levels and immune responses throughout the day, which may play a critical role in how patients respond to asthma treatments. Jha stated:

“The idea that the time of day, or the season of the year, affects our health and how we respond to treatments is something we're seeing increasing evidence of.”

Table 2: Seasonal Variations in Asthma Test Reliability

Conclusion and Implications for Clinical Practice

The implications of this study are significant for clinical practice. By performing lung function tests in the morning, healthcare providers may achieve more accurate diagnoses for asthma, which may lead to better management of the condition. Timely diagnoses can prevent or reduce the frequency of exacerbations, particularly concerning the time-sensitive nature of asthma attacks.

Healthcare practitioners are encouraged to consider both the time of day and seasonal changes when scheduling spirometry tests for patients. A more reliable assessment can ultimately lead to improved treatment plans and patient outcomes. For more detailed findings, refer to the original study: Routine asthma test more reliable in the morning and has seasonal effects, say doctors.

References

[1] Knox-Brown, B., et al. (2025). Effect of time of day and seasonal variation on bronchodilator responsiveness: the SPIRO-TIMETRY study. Thorax.

[2] Cambridge University Hospitals NHS Foundation Trust (CUH).

[3] Royal Papworth Hospital NHS Foundation Trust (RPH).

[4] Medical Xpress. (2025). Retrieved from https://medicalxpress.com/.