#291 CBC Abnormalities Triple Distilled

August 25, 2021 | By Beth Garbitelli

Enjoy this rapid clinical overview of CBC abnormalities based on Episode #167 LIVE! Common CBC Abnormalities Featuring Dr. Mary Kwok! Production & graphics by our very own and very talented Dr. Matt Watto!

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Credits

• Written, Produced, and Hosted by: Matthew Watto MD, FACP; Paul Williams MD, FACP; Beth Garbitelli
• Editor: Matthew Watto MD (written materials); Clair Morgan of nodderly.com

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Show Segments

• Intro, disclaimer, guest bio
• Approaching a mildly abnormal CBC, red flags
• Build the diff, Fy(a-b-) phenotype
• Physical exam and advanced testing
• Polycythemia vera
• Thrombocytopenia
• Outro

Episode #167 CBC Abnormalities

Featuring Dr. Mary Kwok, production & graphics by our very own and very talented Dr. Matt Watto!

Approaching the Mildly Abnormal CBC

• Look at the white count, hemoglobin, platelets, MCV, differential.  
• Don’t knock the CBC: “I love my CBC like I love my morning coffee.” But also be judicious when ordering! 
• Absolute count > percentages
• Anytime you see blasts on a peripheral smear,  basophilia, or severely elevated counts, consult Heme-Onc right away (expert opinion)
• Concerning if absolute eosinophil count of over 1500, less than that is less alarming (can be medication effect v.  allergy). Severe eosinophilia (>5000) associated with greater degree of tissue damage/disease severity (Lam 2021). 
• Smoking is a very common cause (and reversible, Higuchi 2013) of unexplained neutrophilia
• Basophilia is never normal (This raises suspicion for something myeloproliferative)
• Quick associations: Lymphocytosis -?lymphoproliferative, Monocytosis – ?CMML, Basophilia – ?myeloproliferative or AML.
• Repeat a CBC: especially if you can test a hypothesis (smoking cessation vs. medication stop)
• One study suggests that effects from smoking cessation take 2-5 years to show complete resolution of changes in CBC (Van Tiel, 2002)

 Building Your Differential from the Differential

• Harness the power of EMR and trend the CBC to see patterns
• Look at the entire CBC (Don’t miss blasts!)
• First rule-out: infection (chronic or acute)  v. medication effect
• Some patients are Fy(a-b-) phenotype and labs will show ANC <1500. Formerly called ‘benign ethnic neutropenia,’ but non-whiteness should NOT be a medical condition (Merz 2021).  Lab test to confirm: phenotype of RBC
• Rheumatologic process can be concomitant with neutropenia (ie: Felty’s Syndrome -RA, splenomegaly, and neutropenia with recurrent infections)

Physical Exam & Advanced Testing in Leukocytosis

• Focus on: lymph node, spleen, infection
• Sites of infection: skin breaks/sores, hardware in body, feet, joint pain
• Bone Marrow Biopsy: for select patients
• Lymphocytosis (ALC >5000) +/-  lymphadenopathy: consider flow cytometry

Flow Cytometry Basics

• What is flow cytometry? In layperson’s terms “You take someone’s blood, and it’s tagged with all these different markers and then run through a machine, and the cells are plotted on a scatter plot. The pathologist identifies normal populations of cells but they’re really looking for abnormal cell populations. This can help you identify a clonal disorder, like a B-cell process or T-cell process, and can also pick up myeloid or lymphoid blasts” 
• How to impress a consultant? Order flow cytometry if absolute lymphocyte count is high ahead of the heme-onc consult 

Polycythemia Vera Basics

• PV PE tips: look for an enlarged spleen and then see if they have symptoms related to erythrocytosis (ie: “ruddy appearance”) 
• Hx Questions: Erythromelalgia: burning of hands and feet, aquagenic pruritus: itching or burning or stinging from water exposure. Bath or shower causes itching (Mechanism is very poorly understood for AP, does not respond to antihistamine, emerging research is considering targeting JAK2 pathway)
• Check EPO level, is it elevated or low? If low, means RBC are being produced without stimulation and that would make you think of primary erythrocytosis, like polycythemia vera. If EPO is normal, or elevated, something else may be driving, like hypoxia, underlying lung disease, or kidney stimulation (RCC, renal cysts, renal artery stenosis) or tumors. 
• Send EPO level with referral to heme-onc.

Platelet Problems 

• Questions to ask yourself: Is the thrombocytopenia isolated or not? Is this a platelet production problem or a platelet destruction problem?
• Rule out hemolysis (bilirubin, LDH, haptoglobin, +/- direct antiglobulin test). Check HIV, and hepatitis C. Consider sending liver function tests, H. pylori, TSH, HCG (in women), SPEP/UPEP, B12 and folate depending on the clinical history (Tefferi 2005; Lambert 2017)
• In the purple top tube,  there can be some clumping of platelets but this is detectable in the peripheral blood smear. Can give falsely low platelet count. Can run on a blue top (citrated) tube to avoid this (expert opinion)
• ITP is a diagnosis of exclusion, must rule out HIV and Hep C,  B12 or folate deficiency, thyroid disorders, liver dysfunction (esp. cirrhosis), H. pylori, rheumatologic disorders, medications ( esp: heparin, chemo, antidepressants, antibiotics)
• Thrombocytopenia is not an uncommon presentation of cirrhosis (Hancox 2013)

Goal

Listeners will review tops pearls from Curbsiders episode #167 LIVE! Common CBC Abnormalities

Learning objectives

After listening to this episode listeners will…

1. Identify and interpret the key values (parameters) listed in a CBC with differential. 
2. Recognize thrombocytopenia, generate a differential diagnosis, and order appropriate initial testing.
3. Generate a differential diagnosis for erythrocytosis (polycythemia) and perform appropriate follow up testing.
4. Generate a differential diagnosis, take a relevant history and perform appropriate follow up testing for leukocytosis and leukopenia. 
5. Recognize who needs a referral to hematology for common CBC abnormalities.

Disclosures

The Curbsiders report no relevant financial disclosures. 

Citation

Garbitelli B, Watto MF, Williams PN. “#291 CBC Abnormalities Triple Distilled”. The Curbsiders Internal Medicine Podcast. http://thecurbsiders.com/episode-list Final publishing date August 23,, 2021.