A reference interval is not a target, and a result outside one is not a diagnosis
Two sources of noise sit under every number: how reproducible the assay is, and how much the analyte varies within the same person on the same day.
HbA1c
Glycated haemoglobin as an endpoint, its lag, and its failure modes.
What the trials monitored, and what that implies about routine practice
The argument for a baseline panel is that it makes every subsequent result interpretable. The argument against frequent monitoring is that noise accumulates faster than…
Reading HbA1c in the presence of anaemia
The alternatives with shorter windows, what they measure, and why they are rarely ordered.
Vitamin D, adiposity, and a volume-of-distribution problem
What the trials measured, which in the case of micronutrients is very little.
The glycaemic panel before treatment: what is worth measuring and when
The assay is not the problem. The interpretation of a lagging integral as a current measurement is the problem.
What the trials monitored, and what that implies about routine practice
Every additional analyte raises the probability of a flagged result and lowers the average information content of the panel.
A reference interval is not a target, and a result outside one is not a diagnosis
A twelve-analyte panel in a perfectly healthy person has roughly even odds of producing at least one flagged result.
A reference interval is not a target, and a result outside one is not a diagnosis
Almost every misreading of a laboratory panel is a misunderstanding of what a reference interval is and how much a result has to move before the movement means anything.
The out-of-range flag is a statistical convention with a printer attached
The arithmetic of the reference change value, worked for the analytes that matter here.
The out-of-range flag is a statistical convention with a printer attached
A flag is a probability statement about a population. It is not a statement about the person holding the printout.
Falling ferritin is not always falling iron
A substantial proportion of the abnormal results generated during rapid weight loss are consequences of the weight loss rather than findings about the person.
HbA1c and its lag: what a result three months old is telling you
HbA1c integrates roughly three months of glycaemia with the most recent weeks weighted most heavily. Almost every misreading of it is a misreading of that weighting.
What has to change before a change has happened
A flag is a probability statement about a population. It is not a statement about the person holding the printout.
EGFR, cystatin C, and the check on the check
The reference interval for alanine aminotransferase in most laboratories is derived from a population that included people with undiagnosed fatty liver.
Why your laboratory interval differs from the one in the textbook
A twelve-analyte panel in a perfectly healthy person has roughly even odds of producing at least one flagged result.
Rapid weight loss moves eight analytes for reasons that have nothing to do with the drug
A substantial proportion of the abnormal results generated during rapid weight loss are consequences of the weight loss rather than findings about the person.
Vitamin D, adiposity, and a volume-of-distribution problem
Which markers are informative, which are confounded, and which move for reasons unrelated to nutrition.
Which results should be repeated before they are investigated
Timing is the whole of the post-cessation panel: draw it too early and it measures the treatment period.
Which results should be repeated before they are investigated
What the pivotal programmes measured and how often, which is a more defensible template than most published monitoring schedules.
Falling ferritin is not always falling iron
The panel drawn during a week of vomiting is measuring the vomiting.