Someone has a repeatable random urine that is never above the 5th percentile in creatinine-normalized gamma-carboxy-glutamic acid.
Is there an interpretation that is healthful? If there is, low urinary levels are not a good marker. There is no such thing as a marker that is a function of one variable, but if a marker can be found that has only negative interpretations of its multiple variables, then that is a potentially good marker.
I see two unhealthful interpretations:
- The person is deficient in vitamin K (and if this is in part due to taurine deficiency, it will not do to simply supplement vitamin K) and the pool of proteins that are under-carboxylated that is turning over more or less normally reflects that. If one supplements vitamin K, taurine, extra fat, and emulsifier (such as lecithin), and the person eventually goes from the 5th percentile to the 95th percentile, check other measures of vitamin K status, and if those are good, mission accomplished. If not, consider the second baleful interpretation of the original urinalysis results.
- The person is deficient in (a) either turnover of vitamin K modified proteins or (b) general protein turnover.
If we focus on developing markers that have no healthful interpretations (high cholesterol is not one of them), does it bloody matter which unhealthful interpretation is more correct? The marker is useful either way in detecting a problem and in following the solution(s) through to completion and in checking for side effects of any supplementation errors.
- High B12 in urine – probably means heavy supplementation, likely means vitamin adequacy, but is not unambiguous because it could be very bad – although rare, it could be a sign of chronic myelogenous leukemia.
- High taurine in urine – may mean nothing more than heavy supplementation or a seafood rich diet. Low taurine in urine may mean nothing more than low consumption plus low synthesis. Not so clear, but clinical data could make this more intelligible.
- High methylmalonic acid in urine, given no antibiotics: I do not know a good interpretation of this. It is bad, period. Good marker, possibly.