CPK levels
CPK levels was a medical test. 

In 2368, after Deanna Troi and William T. Riker became comatose, Doctor Beverly Crusher scanned Keiko O'Brien. The Ullians were suspected as being involved in an attack on Troi and Riker. At the time of the scanning, Keiko was believed to be the only person aboard the  who underwent a memory probe by the Ullians. The scans revealed Keiko was normal, including her CPK levels.
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Medical measurements