Start with a baseline. A result taken before anything started converts most later ambiguity into a simple comparison, and it cannot be obtained retrospectively.
Same laboratory, same method, same time of day, same fasting state. Between-laboratory differences on several common analytes are larger than the changes people are trying to detect.
Timing matters per analyte: cortisol and testosterone are diurnal, triglycerides are postprandial, and creatinine responds to hydration and to recent training. Fixing the conditions removes most of the noise.
External quality assurance schemes document between-laboratory differences on common analytes that routinely exceed the size of clinically interesting changes.
The caveat is that a panel is not a diagnosis and interpreting one is a clinician's job, particularly when several values move together.
Decide the action for each result before you order the test.
3Worth adding that the collection tube and how long the tourniquet was on move several of these analytes. – Dr_Rosalind_Achebe 8 months ago add a comment