How do I interpret an ALT trend across three draws?

This is a question about interpretation, not about whether to act — I will take action questions elsewhere.

I have read the primary source rather than the summary, which has left me with more questions.

I understand the headline. I do not understand the footnotes, and the footnotes look important.

How should I read this, and where are the traps?

Answering this needs to distinguish screening from monitoring. A screening panel looks for the unexpected; a monitoring panel tracks something you already have a reason to watch.

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.

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.

Pre-analytical factors — posture, tourniquet time, fasting, sample handling — are the largest source of error in routine biochemistry, well ahead of the analysis itself.

One out-of-range value on a twenty-analyte panel is expected. Two on a repeat is a finding.

Standardise the conditions — same time of day, same fasting state, same laboratory — or you are measuring the conditions rather than yourself.

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.

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.

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.

Decide the action for each result before you order the test.

edited 13 Apr 2026 by Dr_Nadia_Farsi — fixed an arithmetic slip in the third paragraph

Before reacting to any single value, check whether it is outside the interval by an amount larger than the assay's own variation.

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.

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.

The honest position is that most people order too many analytes and too few time points, when the reverse would be more informative.

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.

The caveat is that a panel is not a diagnosis and interpreting one is a clinician's job, particularly when several values move together.

Same laboratory, same time, same fasting state, or the comparison is not a comparison.