Further investigations of erythrocytosis
Useful investigations for distinguishing primary and secondary erythrocytosis include:
- FBC:
- the following are present only in primary erythrocytosis:
- white cell count shifted to left (neutrophils)
- platelets and nucleated red blood cells increased
- the following are present only in primary erythrocytosis:
- ESR is usually low (less than 5mm/h) in both primary and secondary disease
- leukocyte alkaline phosphatase:
- raised in primary disease but may also be raised in infection or thrombosis
- raised in primary disease but may also be raised in infection or thrombosis
- vitamin B12 levels are increased in primary disease, predominantly due to increased transcobalamin III levels
- chest X-ray
- abdominal ultrasound or CT:
- to detect renal, hepatic or uterine pathology, and/or hepatosplenomegaly may be positive in secondary disease
- to detect renal, hepatic or uterine pathology, and/or hepatosplenomegaly may be positive in secondary disease
- arterial oxygen tension (PaO2) and O2 saturation measurement - decreased in secondary disease
- haemoglobin O2 affinity (P50) - may be raised in secondary disease if high affinity abnormal haemoglobins
- radioimmunoassays, ELISA - to measure serum levels of erythropoietin; raised in secondary erythrocytosis
- in vitro culture of erythroid progenitors - occurs without addition of erythropoietin in primary disease; only available in specialist labs
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