Episode 009: Cytopenias Series Pt. 1 - Thrombocytopenia

One of our most common consults in hematology is teams seeking guidance for workup and management of thrombocytopenia. In this episode, we cover our approach to this hematologic conundrum.

Major Points Covered:
Thrombocytopenia is defined as a platelet count <150K
- Mild: 100-150K
- Moderate: 50-100K
- Severe: <50K
- We get really worried when <20K (risk of spontaneous bleeding)

What to ask in history and in chart review:
- How quickly did the platelets drop - this is just as important as the absolute number; platelets may still be “normal” but have dropped significantly!
- Mucosal bleeding? Menstrual bleeding?
- Rashes?
- Infections/Meds/Toxins?
- Constitutional symptoms
- Weight loss

Our approach to a differential diagnosis - analogous to everyone’s favorite approach to renal AKI: “pre”, “intra,” and “post”:
Pre: Infections/Meds/Toxins
- 1st: HIV, Hepatits
- 2nd: EBV, CMV, Histoplasmosis
Intra: Primary bone marrow failure
Post: Destructions/consumption/splenomegaly (Cirrhosis, too)
- DIC
- ITP
- TTP
- Platelet clumping

Workup:
- Smear - helps to quickly rule in or rule out a lot of the post-BM issues that are emergencies!
- Citrated platelet count (to rule out platelet clumping)
- Repeat CBC
- Coags (PT/PTT/INR)
- Fibrinogen
- HIV serologies
- Hepatitis B/C serologies
- +/- Haptoglobin (note: in liver disease, you can have low haptoglobin)
- Don't send SPEP/IFE!
- If there is no abdominal imaging, consider abdominal ultrasound to evaluate for cirrhosis and/or splenomegaly

References:
https://www.sciencedirect.com/topics/medicine-and-dentistry/hypersplenism (Textbook of Gastrointestinal Radiology, 3rd edition 2008)- 90% of platelets in spleen at one time

https://pubmed.ncbi.nlm.nih.gov/29978544/ (J Thromb Hemostasis 2018)- Platelet threshold for bleeding risk

https://www.bjanaesthesia.org/article/S0007-0912(18)30753-0/fulltext#fig1 (British Journal of Anesthesia 2019)- Perioperative thrombocytopenia (Look at Figure 1)

https://ashpublications.org/blood/article/131/8/845/104418/How-I-treat-disseminated-intravascular-coagulation (Blood 2018) - DIC with normal fibrinogen (Look at case 1, Table 2 shows good diagnostic criteria)

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