Originally Posted by drunkenmonkey
Is there a product we can purchase commercially that would allow us to test his platelets at home?
No, not practically. You would need to have a microscope and be able to read blood smears to do this at home. The machines that run the test range at about $45,000 US on up.
Severely low platelets can be fatal so daily checking to make sure they are going up is important. If not, then additional medications may be necessary. You are correct that the steroids are for immune system diseases however if you have certain infections, then you can have a secondary immune destruction of cells that persists only while the overall infection is present. A common cause of this is tick fever. It is a blood borne disease that can be contracted through tick bites.
Other tests.... the Parvo test for dogs can be used to test for panleukopenia (which is different from feline leukemia or FIV or FIP). While this isn't common for platelets, it can affect the neutrophils and may be have an indirect impact on the platelets. A tick panel may be useful depending upon demographics. Many times the tick is never seen. A tick could have bitten and been then killed by the cat months ago yet have transmitted a rickettsial disease. Doxycycline, an antibiotic, is often used for many tick borne diseases. Further tests like coagulation panel, radiographs and ultrasound, etc. could be helpful to rule out other problems. If any lymph nodes are enlarged, then lymph node aspiration cytology (sticking a needle in it and getting a sample) would be extremely important.
I hope that all goes well, please keep us updated.