Ikterische Probe

An ikterische Probe is a sample whose serum or plasma shows a strong yellow, orange or brownish colour instead of the usual pale straw tone. The colour comes from bilirubin, the pigment produced when red blood cells are broken down and normally processed by the liver. When more of it circulates than usual, it is visible in the separated sample long before anyone would notice anything about the person who gave it.

The laboratory records the discolouration for a technical reason, because bilirubin absorbs light in a range that several photometric methods also use. A strongly coloured sample can therefore make individual measurements too high or too low, depending on the method.

Modern analysers quantify the colour as an index alongside the results, which is why the comment on a report is a measured statement about the specimen and not an impression. Depending on the analyte, the laboratory then releases the value with a note or holds it back and asks for a new sample. Where a value is held back, the akkreditiertes Labor states what it needs, and that requirement is not open to discussion at the counter.

For a pharmacy this means close to nothing in clinical terms and quite a lot in terms of communication, because the pharmacy did not observe the discolouration, does not assess it and cannot say what caused it.

Bilirubin is raised for a long list of reasons, some of them entirely benign and lifelong and others not, and separating them requires a physician with the history in front of them.

The correct handling at the counter has three steps:

1. Pass on the laboratory comment in the words the laboratory used.
2. Say plainly that the comment describes the sample and not the person.
3. Recommend that the person take the report to their own physician.

Speculating about causes at the counter is out of place, and a wrong guess in either direction is actively harmful.

The term belongs with its two neighbours, because Hämolyse and the lipämische Probe are the other two interference findings that appear as standing comments on laboratory reports, and all three describe the specimen and not the patient.

The three findings differ in what causes them. Haemolysis is usually caused during collection and handling, and lipaemia usually by a recent meal, whereas an icteric sample describes something about the person and is no Präanalytik error at all. That distinction matters, because a repeat draw solves the first two and changes nothing about the third.