Synopsis
Use the absolute reticulocyte response and a coherent haemolysis profile to distinguish red-cell underproduction, loss and destruction, then select immune, membrane, enzyme or mechanical testing.
- Use the absolute reticulocyte count, not the percentage alone. A percentage can appear high simply because the circulating red-cell denominator is low.
- Ask whether the response is appropriate for the depth and duration of anaemia. Reticulocytes take time to rise, and severe iron, B12 or folate deficiency can limit a response despite haemolysis.
- A typical haemolysis pattern combines raised indirect bilirubin and LDH, low haptoglobin, reticulocytosis and film change, but inflammation, liver disease, ineffective erythropoiesis and recent transfusion can alter individual markers.
Key red flags
Back or abdominal pain, dark urine, haemoglobinaemia, marked haptoglobin depletion and acute kidney or potassium disturbance suggest red-cell destruction within the circulation.
Investigation priorities
Measure effective marrow erythroid output in relation to the anaemia.
Management branches
Haemoglobin is falling or jaundice, dark urine, splenomegaly or a regenerative count suggests red-cell destruction.
- First-line testing is FBC, absolute reticulocytes, film, bilirubin fractions, LDH, haptoglobin, DAT, renal profile and urinalysis, alongside observations and a bleeding assessment.
- Check prior counts, transfusion and medicine timing, liver disease, infection, pregnancy and prosthetic valves; an alternative diagnosis is blood loss when reticulocytosis occurs without a convincing destructive profile.
The haemolysis profile is supported and the patient is physiologically stable enough for cause-directed testing.