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The CBC, loved by surgeons, hated by everyone else.  Really it’s the WBC count that is so controversial.  But many of us don’t know some of the subtle but important aspects of the CBC that we may or may not have learned in medical school but have forgotten.

  • Automated Diff: Routinely done by Coulter counter when stream of cells passes through a spectrometer.  Can pick up bands, blasts, and abnormal RBC morphology, such as schistocytes
  • Manual Diff: Only done if ordered or there are red flags on the automated diff, which may vary by hospital but typically includes some of the following: abnormal RBC morphology, bands >11%, or blasts.  Elevated WBC count alone does NOT usually trigger a manual dif.

If you are not facile with the differential, toxic granulation, Dohle bodies, vacuoles, and atypical lymphs read below because YOU SHOULD BE!

You should also be aware that RBC morphology showing Howell-Jolly bodies can signify hyposplenism, leukemia, thalassemia, or pernicious anemia and the first two of these are associated with decreased immunity.  Also RBC Pappenheimer bodies: can signify splenectomy, MDS, sickle cell disease, sideroblastic anemia, hemolysis or lead poisoning, the first three of which can be associated with decreased immunity

Another useful strategy is how to handle an elevated WBC count thatyou don’t think is critical and is just due to demargination.  These WBC counts will usually be between 11-16, although they can be higher.  I usually order a Sed rate and a CRP.  If either or both of these are both normal, you can probably blow off the elevated WBC count.  If you only order one, the CRP is probably more sensitive

Cellulitis Pitfalls

Is it Cellulitis for Necrotizing Fasciitis?

Worry: recent surgery, pain out of proportion to exam, skin necrosis, bullae or hypotension.

Rubor:  Infections that begin in the deep soft tissues may not have pink skin initially

Calor:  Fever may be absent, especially when Tylenol or Advil are being used.

Dolor:  Post-op pain may be erroneously attributed to surgery rather than a deep infection.  Pain may be absent due to nerve damage or due to neuropathy in patients with diabetes.

Tumor: Exam and/or radiographs may show only edema, with no evidence of gas in the tissue.

Other: Nausea, vomiting or diarrhea may be manifestations of  group A streptococcal toxins, but may be wrongly attributed to a viral illness.

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