From the Guidelines
For a patient with consistently elevated hemoglobin levels (15.8 and 15.5) and obstructive sleep apnea (OSA), I recommend ordering a complete blood count (CBC) with differential, serum erythropoietin level, arterial blood gases, iron studies (including ferritin, iron, TIBC), and overnight oximetry. These tests will help determine if the elevated hemoglobin is secondary to OSA-induced hypoxemia or if there's an underlying primary polycythemia 1. OSA commonly causes secondary polycythemia as the body produces more red blood cells in response to intermittent hypoxia during sleep. However, it's essential to rule out polycythemia vera, a myeloproliferative disorder.
Some key points to consider when evaluating these patients include:
- The importance of effective treatment of OSA, which can help normalize hemoglobin levels by improving oxygenation 1
- The need to monitor compliance with CPAP therapy and follow-up hemoglobin levels at regular intervals to assess response
- The potential need for hematology consultation if hemoglobin remains elevated despite adequate OSA treatment
Given the strong recommendation for positive airway pressure therapy in adults with OSA and no significant comorbidities 1, it is crucial to initiate this treatment while also investigating the cause of elevated hemoglobin levels. The choice of PAP initiation in the home or lab should be based on access, cost-effectiveness, patient preference, sleep clinician judgement, and other factors 1.
Key lab orders to consider include:
- Complete blood count (CBC) with differential
- Serum erythropoietin level
- Arterial blood gases
- Iron studies (including ferritin, iron, TIBC)
- JAK2 mutation testing (if polycythemia vera is suspected)
- Overnight oximetry to assess oxygen saturation during sleep.
From the Research
Lab Orders for Hb Consistently 15.8 and 15.5 with OSA
To determine the necessary lab orders for a patient with consistently high hemoglobin (Hb) levels of 15.8 and 15.5 with obstructive sleep apnea (OSA), the following points should be considered:
- The patient's high Hb levels may be indicative of secondary polycythemia, which can be caused by OSA 2
- However, it is also important to rule out other underlying conditions, such as polycythemia vera (PV), which can be masked by secondary causes of erythrocytosis like OSA 3
- Lab orders may include:
- Complete Blood Count (CBC) to evaluate Hb, hematocrit, and other blood cell counts
- Erythropoietin (EPO) level to help differentiate between primary and secondary polycythemia
- Janus Kinase 2 (JAK2) mutation testing to aid in the diagnosis of PV
- Bone marrow biopsy to assess for bone marrow findings consistent with PV
- The patient's OSA diagnosis and treatment with continuous positive airway pressure (CPAP) should also be taken into consideration, as CPAP treatment has been shown to reduce Hb and hematocrit levels in patients with OSA 2
Additional Considerations
- The patient's age, medical history, and other risk factors should be taken into account when interpreting lab results and determining the need for further testing or treatment
- The possibility of phlebotomy or hydroxyurea treatment should be considered if the patient is diagnosed with PV, as these therapies have been shown to improve outcomes and reduce the risk of thrombosis 4, 5, 6