C5.10 Haematology and biochemistry
Polycythaemia should be confirmed as being secondary to COPD by blood gas measurement that demonstrates hypoxaemia. The possibility of sleep apnoea or hypoventilation should be considered if polycythaemia is present but oxygen desaturation or hypoxaemia on arterial blood gas tests are absent when the patient is awake.
Hyperthyroidism and acidosis are associated with breathlessness. Hyperventilation states are associated with respiratory alkalosis. Hypothyroidism aggravates obstructive sleep apnoea. Harrison et al 2014 performed a multicentre prospective study of exacerbations of COPD requiring hospital admission in 1343 patients with spirometry confirmed COPD. The authors reported the novel finding of an association between thrombocytosis (>400/mm3 on admission) and mortality. Thrombocytosis (after controlling for confounders) was associated with an increased 1 year all-cause mortality and an increased in hospital mortality (OR 1.53 (95% CI 1.03 to 2.29, p=0.030) and OR 2.37 (95% CI 1.29 to 4.34, p=0.005)) respectively (Harrison 2014) [evidence level III-2].
The Thoracic Society of Australia and New Zealand Alpha1 Antitrypsin Deficiency Position Statement indicates that testing for alpha1 antitrypsin deficiency (AATD) should be considered in all patients with chronic airflow obstruction (Dummer 2020). The prevalence of severe homozygous AATD has been estimated at approximately 1 in 4,500 in European populations (Blanco 2006). Available data from 15 cohorts in Australia and New Zealand suggest that the prevalence of affected individuals is around 1 in 4,000 (de Serres 2002). Tobacco smoking is still the most important risk factor for COPD even in this group.< Prev Next >