Dr Kola Tytler MBBS CertHE MBA MRCGPClinical Lead • iatroX
Recommended investigations to determine the underlying cause of hypoxemia and erythrocytosis include:
- Full history and physical examination focusing on symptoms and signs suggestive of primary polycythaemia vera (e.g., pruritus, splenomegaly), secondary causes (cardiopulmonary disease, renal disease), and apparent erythrocytosis (smoking, dehydration, diuretics) NICE CKS.
- Measure oxygen saturation by pulse oximetry at rest to assess hypoxemia; abnormal values (<92%) suggest possible secondary erythrocytosis due to cardiopulmonary disease NICE CKS,NICE NG202.
- Blood tests including haemoglobin, haematocrit, mean corpuscular volume, white blood cell count, platelet count, liver function tests, urea and electrolytes, and estimated glomerular filtration rate to evaluate hematologic status and exclude renal or hepatic causes NICE CKS.
- Repeat blood tests after a minimum of two months following interventions to improve hypoxia (e.g., smoking cessation, oxygen therapy) to confirm persistence of erythrocytosis before further investigation NICE CKS,NICE NG115.
- Consider measuring erythropoietin level: low in polycythaemia vera (primary) and raised in secondary erythrocytosis NICE CKS.
- JAK2 V617F mutation testing to confirm or exclude polycythaemia vera if suspected clinically or on blood results NICE CKS.
- Urine dipstick analysis to screen for renal causes NICE CKS.
- Chest radiograph and consider arterial blood gases to assess lung pathology and degree of hypoxia, especially in context of lung disease or long COVID NICE CKS,NICE NG202.
- Screen for obstructive sleep apnoea/hypoventilation syndrome with sleep studies (respiratory polygraphy and possibly transcutaneous CO2 monitoring) if clinical suspicion exists, particularly in patients with hypoxaemia and risk factors such as obesity Mino et al. 2026.
- Monitor cardiovascular risk factors and assess need for referral if primary haematological disorder is suspected or if hypoxaemia and erythrocytosis persist despite treatment NICE CKS,NICE NG115.
Key References
- NICE CKS: Breathlessness
- NICE NG115: Chronic obstructive pulmonary disease in over 16s: diagnosis and management
- NICE NG202: Obstructive sleep apnoea/hypopnoea syndrome and obesity hypoventilation syndrome in over 16s
- (Mino et al., 2026): Transient Oxygen Desaturation Associated with Persistent Right Venous Valve-Mediated Right-to-Left Atrial Shunt in Term Neonates.
- (Maneechotesuwan et al., 2026): Beyond the Lungs: A Narrative Review of Cardiopulmonary Risk Reduction and Management Perspectives in Thai COPD Patients.
- (Hassan et al., 2026): Perioperative Cardiac Arrest Complicated by Acute Pulmonary Edema Following Myomectomy: A Case Report from a Resource Limited Sitting.