Diagnosis of Erythrocytosis
The diagnosis of erythrocytosis begins with a full blood count (FBC). Doctors then perform tests to identify whether the condition is primary, secondary, or relative. Doctors use a step-by-step approach to determine whether to treat erythrocytosis or simply monitor it, since the condition has many causes.
Step 1: Blood Tests
The first clue comes from routine blood tests showing:
Elevated red blood cell count (RBC)
Increased haemoglobin (Hb)
High haematocrit (Hct)
In men, haematocrit levels above 52% and in women above 48% may prompt further investigation. Blood viscosity also increases at these levels, raising the risk of complications.
Step 2: Rule Out Relative Erythrocytosis
Doctors first determine whether the red cell count is truly elevated or whether reduced plasma volume is responsible. Furthermore, dehydration, diuretic use, or acute illness can cause relative erythrocytosis, which resolves with rehydration and correction of fluid balance.
Step 3: Evaluate Oxygen Levels and EPO
Pulse oximetry and arterial blood gases help assess oxygen levels in the blood
Erythropoietin (EPO) levels are crucial to classify the erythrocytosis:
Low EPO suggests a primary cause, like polycythaemia vera
High EPO points to a secondary cause, such as lung disease or kidney tumours
Step 4: Genetic and Bone Marrow Tests
In suspected primary erythrocytosis:
A JAK2 gene mutation test is performed. Thus, most cases of polycythaemia vera are JAK2-positive.
Doctors may perform a bone marrow biopsy to assess cellular activity and rule out other haematological disorders.
Imaging and Other Investigations
Depending on suspected causes, doctors may request:
Chest X-rays or CT scans – For lung disease or tumours
Abdominal ultrasound or CT – To check the kidneys or liver
Sleep studies, if sleep apnoea is suspected
Diagnosis of Erythrocytosis In South Africa
Some specialist centres in South Africa provide access to genetic testing. Additionally, bone marrow biopsies since availability can be limited in other areas. Primary care clinics often rely on basic blood tests and chest X-rays. Furthermore, healthcare providers maintain a high index of suspicion in areas with limited access to advanced diagnostics.
The diagnosis of erythrocytosis should be thorough to prevent missed cases of blood cancer or secondary causes like TB-related lung damage. Finally, timely diagnosis allows patients to receive the correct treatment and avoid dangerous complications.
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