WBC high But Platelets normal

My father is a heart  patient, last week he went for routine blood tests, in his blood report the WBC - 48000 is very high but rest of the things are normal like Platelets - 213000, Hemoglobin - 13.8.
Now doctor has recommend him Leukemia differentiation Panal test.
Does person can have Leukemia due to only WBC high count or it may be some other type of infection?
He does not have any other symptoms like fever, digestive problem but he has diabetes, Blood pressure and heart problems.  

[Londres70]

With a WBC that high, it is probably not a bad idea to rule Leukemia.  It is possible to see counts that high with an infection, so both possibilities should be ruled out.