Thrombocytopenia (Low Platelet Count) (cont.)
How is thrombocytopenia diagnosed?
As mentioned earlier, thrombocytopenia is usually
detected incidentally from routine blood work done for other reasons. Platelets
are a component of the complete blood count (CBC) which also contains information on red blood
cells and
white blood cells.
If thrombocytopenia is seen for the first time, it is
prudent to repeat the complete blood count in order to rule out
pseudothrombocytopenia (see above). If
the repeat CBC confirms low platelet counts, then further evaluation can begin.
Once detected, the cause of thrombocytopenia may be investigated by the
doctor. The most essential part of this evaluation includes a thorough physical
examination and medical history
of the patient. In the medical history, the complete
list of all medications is routinely reviewed. Some of the other important
components of the history include reviewing previous known history of low
platelet count, family history of thrombocytopenia, recent infections, any
previous cancers, other autoimmune disorders, or liver disease.
A review of the symptoms related to excessive bleeding or bruising can also
provide additional information. As a part of a thorough physical examination,
special attention may be given to the skin and mucus membrane in the oral cavity
for petechiae or purpura or other signs of bleeding. On the abdominal
examination, an enlarged spleen
(splenomegaly) can provide important diagnostic
clues.
The urgency to perform additional testing and evaluation
is largely dependent on how low the platelet count is on the blood count, and
what the clinical situation may be. For instance, in a person who needs a
surgery and has a
platelet count of less than 50 the investigation will take precedence over one
whose thrombocytopenia was detected on a yearly blood work with a platelet of
100.
A comprehensive review of the other components of the CBC is one of the most
important steps in the evaluation of low platelet count. The CBC can tell us
whether other blood disorders may be present, such as, anemia (low red cell
count or hemoglobin), erythrocytosis (high red blood cell count or hemoglobin),
leukopenia (low white cells count), or leukocytosis (elevated white blood cell
count). These abnormalities may suggest bone marrow problems as the potential
cause of thrombocytopenia. Abnormally shaped or ruptured red cells
(schistocytes) seen on the blood smear may suggest evidence of HELLP, TTP, or
HUS (see above).
Another clue in the CBC is the mean platelet volume or
MPV, which is an estimate of the average size of platelets in the blood. A low
MPV number may suggest platelet production problem, whereas, a high number may
indicate
increased destruction.
It is important to also review other blood work
including the complete metabolic panel, coagulation panel, and urinalysis.
Certain abnormalities in these tests can suggest advanced liver disease
(cirrhosis), kidney problems (renal failure), or other pertinent underlying medical conditions.
In some causes of thrombocytopenia, such as HIT or ITP,
additional testing with antibodies or assays may be done. Bone marrow biopsy can sometimes be
performed if a bone marrow problem is suspected.
Next: How is thrombocytopenia treated? »
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