Take a deep dive into common CBC abnormalities. We recorded LIVE at joint grand rounds between Walter Reed NMMC and Uniformed Services University with hematologist, Dr. Mary Kwok MD. Topics include: which parts of the complete blood count (CBC) are most important, interpreting the differential, when to order flow cytometry, who needs a hematology consult and simplified approaches to patients with leukocytosis, leukopenia, erythrocytosis and thrombocytopenia.
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Written, Produced and Edited by: Matthew Watto MD, FACP
Cover Art and Infographic by: Matthew Watto MD, FACP
Hosts: Stuart Brigham MD; Matthew Watto MD, FACP; Paul Williams MD, FACP
Guest: Mary Kwok MD
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Look at the white count (WBC), Hemoglobin (Hgb), Platelets (Plt), MCV, and the differential (diff).
Next, calculate the absolute counts e.g. absolute neutrophil count, etc. The absolute counts trump the percentages when reviewing a CBC with diff.
Keep repeating labs until they become normal. Dr. Kwok agrees that an abnormal CBC should be repeated to see if the abnormalities persist.
Smoking and infections commonly cause neutrophilia. Lymphocytosis is suspicious for a lymphoproliferative disorder. Older patients with monocytosis may have CMML.
Smoking is a common cause of neutrophilia. Tell the patient to stop smoking and then repeat the labs.
Blasts, elevated basophils (suggests myeloproliferative neoplasm), absolute eosinophil count over 1500, absolute lymphocyte count over 5000 all warrant a hematology consult. These patients may need bone marrow biopsy.
Are the cells mature or immature? Which type of cell predominates? Hematopathologists are often willing to review abnormal findings.
Blood is tagged with markers. Millions of cells are analyzed and plotted on a scatter plot. Then, a pathologist identifies any abnormal populations of cells e.g. clonal B cells, T cells, myeloid blasts, or lymphoid blasts.
Review previous CBCs to check for chronicity. Review medication exposures to look for culprits. Ask about a history of acute, chronic or recurrent infections. Does the patient have a known rheumatologic disorder?
Check the peripheral smear to look for blasts or other abnormal cells.
Benign ethnic neutropenia can be confirmed by checking an RBC phenotype. Patients who are Duffy null (negative for Duffy A and B) likely have benign ethnic neutropenia.
Rheumatologic diseases may be a cause of neutropenia, but they’re usually symptomatic (NOT an occult process).
Defined as hemoglobin (Hgb) above 16.5 g/dL for a man, or above 16 g/dL for a woman (Tefferi A. UpToDate 2019).
Check for splenomegaly. Repeat the CBC. Next, check an EPO level. A low EPO level suggests a primary process live PV. Consider sending a JAK2 mutation for patients with a low EPO level and clinical suspicion for PV. A normal or elevated EPO level suggests a secondary erythrocytosis from hypoxia, a renal process or EPO secreting tumor.
Aquagenic pruritus is stinging, burning or itching that occurs in response to water exposure. Erythromelalgia is intermittent burning pain (often severe) in hands or lower extremities. It’s believed to be caused by blocked blood vessels.
Coach was Stuart’s patient with low testosterone, obstructive sleep apnea and elevated Hgb from secondary erythrocytosis. He requested testosterone replacement therapy. The patient was noncompliant with CPAP at baseline, but improved his efforts to try and drop his Hgb. He eventually was given testosterone replacement therapy, but his Hgb shot up to nearly 20 g/dL and he had to stop it again.
Dr. Kwok hasn’t seen much of a drop in Hgb for her patients on CPAP for sleep apnea.
Dr. Watto had a single patient like Coach who wanted testosterone therapy, but had severe secondary polycythemia. A local hematologist conducted regular therapeutic phlebotomy to keep the patient’s Hgb at a safe level while receiving testosterone replacement. Note: the patient had a high Hgb despite compliance with his CPAP and smoking cessation.
Dr. Kwok has not seen platelets improve much after treating patients for H. pylori.
First repeat the CBC. Next, check a peripheral smear. Use a blue top tube to overcome any platelet clumping noted on the smear. 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)
Immune thrombocytopenia (ITP) is a diagnosis of exclusion.
Listeners will identify common abnormalities found in the complete blood count, perform appropriate follow up testing if needed and recognize who needs referral to hematology.
After listening to this episode listeners will…
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Dr Kwok reports no relevant financial disclosures. The Curbsiders report no relevant financial disclosures.
Kwok M, Brigham SK, Williams PN, Watto MF. “#167 LIVE! Common CBC Abnormalities with Mary Kwok MD”. The Curbsiders Internal Medicine Podcast. http://thecurbsiders.com/podcast. August 26, 2019.
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Comments
"Smoking is a common cause of neutrophilia. Tell the patient to stop smoking and then repeat the labs." How long does a chronic smoker need to abstain before seeing changes on H/H? Thank you
How long do you wait to repeat CBC?! Thank you...