ANSWER 4
The peak flow pattern shows a degree of diurnal variation. This does not reach the diag-
nostic criteria for asthmabut it is suspicious. The mean daily variation in peak flow from
the recordings is 36 L/min and the mean evening peak flow is 453 L/min, giving a mean
diurnal variation of 8 per cent. There is a small diurnal variation in normals and a vari-
ation of#15 per cent is diagnostic of asthma. In this patient the label of ‘bronchitis’ as a
child was probably asthma. The family history of an atopic condition (hayfever in a
brother), and the triggering of the cough by exercise and going out in to the cold also sug-
gest bronchial hyper-responsiveness typical of asthma.
Patients with a chronic persistent cough of unexplained cause should have a chest X-ray.
When the X-ray is clear the cough is likely to be produced by one of three main causes in
non-smokers. Around half of such cases have asthma or will go on to develop asthma over
the next few years. Half of the rest have rhinitis or sinusitis with a post-nasal drip. In around
20 per cent the cough is related to gastro-oesophageal reflux. A small number of cases will
be caused by otherwise unsuspected problems such as foreign bodies, bronchial ‘adenoma’,
sarcoidosis or fibrosing alveolitis. Cough is a common side-effect in patients treated with
angiotensin-converting-enzyme (ACE) inhibitors.
In this patient the diagnosis of asthma was confirmed with an exercise test which was
associated with a 25 per cent drop in peak flow after completion of 6 min vigorous exer-
cise. Alternatives would have been another non-specific challenge such as methacholine
or histamine, or a therapeutic trial of inhaled steroids.
After the exercise test, an inhaled steroid was given and the cough settled after 1 week.
The inhaled steroid was discontinued after 4 weeks and replaced by a $ 2 -agonist to use
before exercise. However, the cough recurred with more evident wheeze and shortness of
breath, and treatment was changed back to an inhaled steroid with a $ 2 -agonist as
needed. If control was not established, the next step would be to check inhaler technique
and treatment adherence and to consider adding a long-acting $ 2 -agonist. In some cases,
the persistent dry cough associated with asthma may require more vigorous treatment
than this. Inhaled steroids for a month or more, or even a 2-week course of oral steroids
may be needed to relieve the cough. The successful management of dry cough relies on
establishing the correct diagnosis and treating it vigorously.
- The three commonest causes of persistent dry cough with a normal chest X-ray are
asthma (50 per cent), sinusitis and postnasal drip (25 per cent) and reflux oesophagitis
(20 per cent). - Asthma may present as a cough (cough variant asthma) with little or no airflow
obstruction initially, although this develops later. - Persistent cough with normal chest examination is unlikely to have a bacterial cause or
respond to antibiotic treatment.