Normal Bone Marrow Cellularity in a 70-Year-Old
The expected overall cellularity in a bone marrow biopsy of a normal 70-year-old is 30% ± 10, corresponding to answer choice D.
Age-Related Changes in Bone Marrow Cellularity
Bone marrow cellularity naturally decreases with age, following a predictable pattern:
- In adults, bone marrow cellularity declines approximately 3% per decade 1
- For individuals older than 60 years of age, the normal range is 30% to 60% with a mean of 45% and standard deviation of 15% 1
- Specifically for those in their 70s, the mean cellularity is approximately 40% 2
Evidence-Based Normocellularity Ranges by Age
The most recent and comprehensive research provides the following age-adjusted normocellularity ranges:
- Ages 20-40: 40-70% (mean 55% ± 15%)
- Ages 40-60: 35-65% (mean 50% ± 15%)
- Ages >60: 30-60% (mean 45% ± 15%) 1
Importantly, research has shown that individuals older than 70 years do not show a significant further decrease in cellularity compared to those aged 60-69 years 1. This contradicts older models that suggested a continuous linear decline with age.
Clinical Implications of Age-Adjusted Cellularity
Understanding normal age-related changes in bone marrow cellularity is critical for:
- Avoiding misdiagnosis of hypocellular conditions like aplastic anemia
- Correctly identifying hypercellular conditions like myeloproliferative neoplasms
- Properly assessing bone marrow reserve in elderly patients
Without age adjustment, approximately 13% of AML patients and 29% of MDS patients might be incorrectly classified as having abnormal cellularity 3, 4.
Assessment Methods and Reliability
The most reliable method for determining bone marrow cellularity is through core biopsy examination:
- Bone marrow biopsy is superior to aspirate or buffy coat examination for cellularity assessment 5
- A 1-2 cm core biopsy is preferred for accurate evaluation 3
- Digital image analysis methods show good correlation with pathologist assessment (ICC=0.78) 2
Common Pitfalls to Avoid
- Using the outdated "100% minus age in decades" formula, which overestimates the decline in cellularity
- Failing to account for the wide normal range (approximately 30-60%) in elderly patients
- Relying solely on aspirate samples, which can misrepresent true marrow cellularity in up to 39% of cases 5
- Not considering the increased apoptosis in elderly bone marrow, which contributes to hypocellularity 6
Therefore, when evaluating a bone marrow biopsy from a 70-year-old patient, the expected normal cellularity would be approximately 30% ± 10%, making answer choice D the correct option.