Assay

Full Blood Count (FBC)

Key Words

Full Blood Count, FBC

Specimen Collection

3.4ml EDTA for adults, and where possible, for children >10 years old (Red lid); 1.3ml EDTA for paediatric patients <10 years old (Red lid), do not overfill. If a Kleihauer is also requested, an additional sample bottle is required. If a paediatric ESR is also requested, an additional paediatric 1.3ml EDTA sample bottle is required. These two tests cannot be run from the same sample as the FBC. FBC tests may be added on to samples that are up to 48 hours old, but some sequential tests may not be possible at this point - samples should ideally be less than 24 hours old.

Turnaround time

Next working day

Test indications

Investigations of red cells, white cells and platelets

Interferences

Lipaemia causes a falsely elevated haemoglobin which also affects MCV and MCHC - If the lipaemia is identified during analysis due to these indices being significantly abnormal, then laboratory staff will perform a hyperlipidaemia correction to return the Hb, MCV and MCHC to their true values. Hyperbilirubinaemia does not affect the haemoglobin value but may affect other FBC values. Clots or fibrin strands in samples, platelet aggregates, and/or haemolysis can irreparably damage cellular content in the sample and render most FBC parameters invalid - Samples will be either processed with a disclaimer, processed with the most affected FBC values removed, or rejected entirely depending on the severity of the sample degradation. Samples identified by the laboratory as containing cryoglobulins will be warmed prior to analysis to minimise red cell clumping and the subsequent effect on the FBC results.

Reference Range

See table below. Reference ranges for FBC parameters obtained from Phase II of the Pathology Harmonisation Project.

Minimum retesting interval

N/A