Anaemia Classification Based on Haemoglobin Levels
Anaemia is classified by severity into three categories: mild anaemia (Hb 10.0-11.9 g/dl), moderate anaemia (Hb 8.0-9.9 g/dl), and severe anaemia (Hb <8.0 g/dl). 1
Severity-Based Classification
The European Society for Medical Oncology (ESMO) provides the most widely adopted classification system for anaemia severity:
- Mild anaemia: Hb ≤11.9 g/dl and ≥10.0 g/dl 1
- Moderate anaemia: Hb ≤9.9 g/dl and ≥8.0 g/dl 1
- Severe anaemia: Hb <8.0 g/dl 1
Defining Anaemia: Normal Lower Limits
Anaemia is fundamentally defined as haemoglobin concentration below the normal lower limit, which varies by sex. 1
Standard Definitions:
Important Clinical Considerations:
Use your local laboratory's lower limit of normal range to define anaemia, as normal Hb values vary between populations. 1 This is particularly relevant in the UK and other regions where population-specific variations exist.
Treatment-Related Anaemia Grading (NCI-CTCAE)
For cancer patients receiving treatment, the National Cancer Institute Common Toxicity Criteria provides an alternative grading system 1:
- Grade 0: Within normal limits
- Grade 1: Lower normal limit to 10.0 g/dl
- Grade 2: 8.0 to <10.0 g/dl
- Grade 3: 6.5 to <8.0 g/dl
- Grade 4: <6.5 g/dl
- Grade 5: Death
Clinical Thresholds for Investigation
In iron deficiency anaemia specifically, investigate men with Hb <12 g/dl and postmenopausal women with Hb <10 g/dl more urgently, as lower haemoglobin levels suggest more serious underlying disease. 1 However, any level of anaemia in the presence of iron deficiency warrants investigation, as even mild anaemia may indicate significant pathology including gastrointestinal malignancy 1.
Key Clinical Pitfalls
Do not assume lower haemoglobin values are physiological in elderly patients. 4 The WHO reference values remain valid for older persons, as Hb values below these thresholds are associated with increased mortality and functional impairments even when only slightly decreased 4. A cause for anaemia is found in over 80% of elderly patients when appropriate diagnostic testing is performed 4.
Anaemia severity directly impacts quality of life and is a major contributor to cancer-related fatigue, making accurate classification clinically important beyond just the numerical value. 1