further investigations of erythrocytosis

Last reviewed 01/2018

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

• 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

• 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

• 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