Chapter 1 · Full blood count QC and flagging

The automated FBC analyser must have documented QC at two or three levels at each shift start and at defined intervals. Analyser flags — blast, immature granulocyte, atypical lymphocyte, platelet clump, nucleated red blood cell — must be followed up by morphology review according to the laboratory’s blood film review criteria (ICSH guidelines recommend specific thresholds). Delta check is critical: a haemoglobin drop of more than 20 g/L without clinical explanation requires review.

Chapter 1 · Practical example

Automated FBC — when to trust the result and when to make a film

Not every FBC result from an automated analyser is reliable without review. Flags, abnormal populations, and clinical context must guide the decision to make a blood film.

▲ The situation

An automated FBC on a 7-year-old child shows WBC 14.8 x10^9/L with an atypical lymphocyte and blast population flag. The absolute lymphocyte count is 12.1. The auto-verification rules are designed for adult parameters.

Reference: ISO 15189:2022 Clause 7.3; ICSH FBC Review Guidelines

✓
Good practice

The section head identifies that auto-verification rules for the adult population should not apply to a paediatric sample with a blast flag. A blood film is prepared and reviewed — 60% blast cells are identified. The requesting paediatrician is contacted urgently. The child is referred immediately for paediatric haematology review. ALL is subsequently confirmed.

✗
Poor practice

The result passes the adult auto-verification rules because the WBC, though high, is within the ‘alert’ rather than ‘critical’ range, and the blast flag is not in the auto-verification suppression list. The result is released as mild lymphocytosis — probable viral. The child returns eight weeks later with advanced disease.

● What this means for your practice

Blood film review criteria must specifically address paediatric samples and blast flags. Auto-verification rules that are appropriate for adult populations may be dangerous for children. Maintain a separate paediatric review protocol.