Normal CBC?

Question

If you get a CBC done for a surgery and it all comes back normal, what does this mean? What diseases do I not have?

Answer 1

Whoa, that would fill a textbook.  However, the surgeons are primarily looking for evidence of:

1)  Anemia - this means a low red-blood-cell count.  Since surgery often results in some blood loss, they would not want to operate on someone who is already low on red blood cells.

2)  Infection - As manifested by elevated white blood cell count.  If you are already sick, you are more likely to have a complication after surgery.  Also, if there is an infection from the surgery, the surgeons need to know that it was from the surgery and not from what you had before the operation.  

3)  Abnormal clotting - Platelets are cell fragments that form clots.  If they are too high, you might clot too easily, which can cause blood clots where you don't want them.  If they are low, you are prone to bleed too much from the incisions.

Answer 2

The RBC count, Hgb, Hct, and RBC indices being normal means you aren't anemic.

The WBC count and differential is pretty well useless as a screening test (you really didn't think you had leukemia, did you?). And the platelet count, though it might occasionally uncover a case of thrombocytopenia, isn't worth doing, either.  

Sixty or seventy years ago, when these things were done individually and by hand, you'd have gotten a Hgb or Hct and dispensed with the rest of it. These days, it's easier and cheaper to run the automated panel than it is to do the single test you're really interested in, so you get all the extras, and one hopes there are no "false positive" abnormalities that have to be double-checked.