For reference: cystatin C · creatinine · a GLP-1 receptor agonist.
I am trying to choose between two options that are usually discussed as though only one exists.
I am not optimising for price, but I am not indifferent to it either.
Which axes does this decision turn on?
The short version: a small, well-chosen panel with a baseline beats a large one without.
Delta checks — comparing against your own previous value — are far more sensitive than comparing against a population interval, which is the argument for keeping a series rather than a snapshot.
A sensible core for this population is a full blood count, renal function with electrolytes, liver enzymes with bilirubin, a fasting lipid panel with apolipoprotein B, HbA1c and thyroid-stimulating hormone.
Reference intervals are conventionally the central ninety-five per cent of a reference population, which is the direct cause of the one-in-twenty out-of-range rate on a healthy panel.
The caveat is that a panel is not a diagnosis and interpreting one is a clinician's job, particularly when several values move together.
Keep the full report, not the number. You will need the units and the interval later.
HPLC purity, identity confirmation and quantified content on the vial you actually hold. Reports arrive with the chromatogram attached, not just a number.
Submit a sampleFounded 1998. ISO 9001 and cGMP certified, 1,500+ staff and 200+ patents. The synthesis house behind a great many of the vials that get sent out for testing - batch-specific documentation with every order.
Visit GL BiochemThe honest position is that most people order too many analytes and too few time points, when the reverse would be more informative.
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.
Repeat before you react. A single abnormal value has a substantial probability of being within the combined biological and analytical variation of a normal one.
Pre-analytical factors — posture, tourniquet time, fasting, sample handling — are the largest source of error in routine biochemistry, well ahead of the analysis itself.
Nothing here is medical advice. If something is out of range and you do not know why, that is a consultation rather than a research project.
Same laboratory, same time, same fasting state, or the comparison is not a comparison.
The relevant statistical point is that a ninety-five per cent reference interval means one analyte in twenty will read out of range in a healthy person by construction.
A twenty-analyte panel run on a healthy person will produce, on average, one out-of-range result purely from how reference intervals are constructed. That is arithmetic rather than pathology.
More usefully, haemolysis in the sample raises potassium and several enzymes spuriously. If a result is bizarre, ask whether the sample was flagged before building a theory on it.
External quality assurance schemes document between-laboratory differences on common analytes that routinely exceed the size of clinically interesting changes.
Ordering tests you will not act on generates anxiety and incidental findings, both of which have costs.
One out-of-range value on a twenty-analyte panel is expected. Two on a repeat is a finding.
Before reacting to any single value, check whether it is outside the interval by an amount larger than the assay's own variation.
Keep the reports rather than the numbers. Units, reference intervals and methods all vary, and a bare number two years later is not comparable to anything.
Biological variation data are published per analyte and are the basis for the reference change value — the difference between two results that is larger than noise.
Decide the action for each result before you order the test.
Specifically, this is answerable, and the answer is mostly about which tests rather than how many.
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.
Research-use compounds are not approved for human use, and no panel makes that safer.
Baseline first, then a repeat under identical conditions. Everything else is secondary.
edited 21 Apr 2025 by h_pergande — added the citation requested in comments
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