NewsFeed Voices Science Insight Innovation
December, 2025
December 2025
M T W T F S S
1234567
891011121314
15161718192021
22232425262728
293031  
“Marrow Asleep or Awake?”: William Aird Simplifies Anemia Diagnosis
William Aird/X
Oct 30, 2025, 07:55

“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.

Aabsolute Reticulocyte Count anemia ARC benign hematology Harvard Medical School Health Hematology Hemostasis Hemostasis Today Medicine thrombosis William Aird
NewsFeed