An 80-year-old woman presented with a 6-month history of progressive breathlessness.
On examination, her chest was normal, but there was a large goitre.
Which investigation is most useful to determine whether the goitre is the cause of her breathlessness?
A: bronchoscopy
B: CT scan of neck and chest
C: forced vital capacity
D: respiratory flow–volume loop
E: X-ray of thoracic inlet
Correct answer: D Explanation Pulmonary function tests are the most sensitive indicator of goitre being the cause of her breathlessness. The flow–volume loop will show marked reduction of the peak inspiratory and expiratory flow, unlike most pulmonary causes of breathlessness. Her vital capacity will not be affected by the presence of goitre. Bronchoscopy, CT scan and X-ray of thoracic inlet may have other uses in the diagnostic pathway but will not be the best way to confirm that it is the goitre