“Marrow Asleep or Awake?”: William Aird Simplifies Anemia Diagnosis
William Aird, Professor of Medicine at Harvard Medical School, posted on X:
՛՛1/4
RETIC COUNT
When evaluating anemia, I teach my trainees to start with a simple binary:
Is the bone marrow responding appropriately or not?
That answer lies in a single number: the absolute reticulocyte count (ARC).
2/4
- ARC < 0.12 ×10⁶/µL → hypoproliferative (marrow asleep).
- ARC ≥ 0.12 ×10⁶/µL → hyperproliferative (marrow awake).
It’s a light switch, not a dimmer.
Once the marrow’s “on,” the next question isn’t how high, but why.
3/4
Getting granular (0.15 vs 0.20) adds math, not meaning.
At that point, you’ve already learned the key thing:
the marrow can respond, so look for blood loss or hemolysis, not marrow failure.
4/4
Clinical reasoning often starts binary and gets nuanced later (i.e., decision thresholds are categorical).
The ARC is one of those places where simple still works.
Below 0.12 → asleep.
Above 0.12 → awake.
Everything else is physiology, not management.՛՛
Stay updated with Hemostasis Today.
-
Aug 11, 2026, 08:20Hasan Abbas Zaheer: Strengthening Universal Access to Safe Blood in Pakistan
-
Aug 11, 2026, 08:07Nicola Pozzi: Advancing Hemostasis Through Scientific Collaboration at Hemostasis GRC
-
Aug 11, 2026, 07:50When Access to Care Changes Everything – WFH
-
Aug 11, 2026, 07:41Kevin Land: How Cellular Therapy Is Changing Transfusion Medicine
-
Aug 11, 2026, 07:35Kuldeep Singh Bhadauria: Building the Future of Hemophilia Care in India
-
Aug 11, 2026, 07:28Archil Jaliashvili: When Every Minute Matters Time Becomes a Therapy
-
Aug 11, 2026, 07:05Mavis Agnes Kisakye: Building Sustainable Transition Pathways in Hemophilia Care
-
Aug 11, 2026, 06:48Rishdha Roshad: What Happens to the Brain During Cardiopulmonary Bypass?
-
Aug 11, 2026, 05:53Isaac Okello: Strengthening Sickle Cell Advocacy in Uganda