B. Peripheral tingling during episodes of dyspnoea – Explanation
The British Thoracic Society suggest peripheral tingling is one of the factors which makes a
diagnosis of asthma less likely. His smoking history does not preclude a diagnosis of asthma
Asthma: diagnosis in adults
The 2008 British Thoracic Society guidelinesmarked a subtle change in the approach to diagnosing
asthma. This approach is supported in the updated 2011 guidelines. It suggests dividing patients into
a high, intermediate and low probability of having asthma based on the presence or absence of
typical symptoms. A list can be found in the external link but include typical symptoms such as
wheeze, nocturnal cough etc
Example of features used to assess asthma (not complete, please see link)
| Increase possibility of asthma | Decrease possibility of asthma |
| • Wheeze, breathlessness, chest tightness and cough, worse at night/early morning • History of atopic disorder • Wheeze heard on auscultation • Unexplained peripheral blood eosinophilia |
• Prominent dizziness, light-headedness, peripheral tingling • Chronic productive cough in the absence of wheeze or breathlessness • Repeatedly normal physical examination • Significant smoking history (i.e. > 20 pack-years) • Normal PEF or spirometry when symptomatic |
Management is based on this assessment:
- high probability: trial of treatment
- intermediate probability: see below
- low probability: investigate/treat other condition
For patients with an intermediate probability of asthma further investigations are suggested. The
guidelines state that spirometry is the preferred initial test:
- FEV1/FVC < 0.7: trial of treatment
- FEV1/FVC > 0.7: further investigation/consider referral
Recent studies have shown the limited value of other ‘objective’ tests. It is now recognised that in
patients with normal or near-normal pre-treatment lung function there is little room for measurable
improvement in FEV1 or peak flow.
A > 400 ml improvement in FEV1 is considered significant
- before and after 400 mcg inhaled salbutamol in patients with diagnostic uncertainty and airflowobstruction present at the time of assessment
- if there is an incomplete response to inhaled salbutamol, after either inhaled corticosteroids (200
mcg twice daily beclometasone equivalent for 6-8 weeks) or oral prednisolone (30 mg once daily for
14 days)
It is now advised to interpret peak flow variability with caution due to the poor sensitivity of the test
- diurnal variation % = [(Highest – Lowest PEFR) / Highest PEFR] x 100
- assessment should be made over 2 weeks
- greater than 20% diurnal variation is considered significant
