Hemolysis, lipemia and icterus indices: sample quality in cats and dogs
Before or alongside the chemistry tests, the analyser checks the sample itself: how red, how cloudy and how yellow the serum or plasma is. These three indices describe sample quality, not a disease. A raised index warns that some results on the same form may be falsely high or low.
What it shows
- Hemolysis index — a semi-quantitative estimate of free haemoglobin released from burst red cells (red or pink serum).
- Lipemia index — cloudiness caused by fat, usually triglyceride-rich particles (chylomicrons). The index reflects turbidity more than the actual triglyceride level.
- Icterus index — an estimate of total bilirubin, which makes serum yellow.
All three change how light passes through the sample, and some also interfere chemically or by displacing volume, so the analyser uses them to judge which results can be trusted.
Higher than reference — what it may be a sign of
- Hemolysis. Usually it happens in the tube: difficult blood draw, rough handling, freezing whole blood, delayed separation of serum from cells, lipemia (fatty samples have fragile red cells) or a fluoride-oxalate tube. Less often it is real, inside the body, as in some hemolytic anaemias — the two can be very hard to tell apart; anaemia with haemoglobin in the urine makes true hemolysis more likely. Falsely high results are expected for things abundant in red cells — LDH, AST, magnesium, in some species potassium — and also CK; phosphate may rise with storage. Red cell count and hematocrit read falsely low when hemolysis occurred in the tube.
- Lipemia. Usually a temporary effect after a meal. Lipemia in a fasted animal suggests altered fat metabolism due to disease, such as diabetes or pancreatitis. It can falsely raise haemoglobin, MCH, MCHC, refractometer protein and some bilirubin results, and falsely lower sodium and chloride. The lab can chill and spin the sample at high speed and test the clearer layer below the fat — but not for triglycerides, which need the whole sample.
- Icterus. The yellow colour is real bilirubin, so a raised index is itself a reason to look at bilirubin. At high levels bilirubin can falsely lower some results, including creatinine and total protein; its effect on the blood count is minimal.
Lower than reference
A low or zero index is the usual and desired result: the sample is clear, and its colour or cloudiness is not distorting the other results. It says nothing about disease and is not a measurement of haemoglobin or bilirubin in the blood.
Look at together with
- Potassium, LDH, AST — the results most often questioned in a hemolyzed sample.
- Haemoglobin, hematocrit, blood in urine — whether hemolysis is happening in the body rather than in the tube.
- Triglycerides — when the lipemia index is high in a fasted animal.
- Total bilirubin — the actual measurement behind a high icterus index.
Units and conversion
These indices have no units on the form. The analyser gives a number that only roughly tracks free haemoglobin or bilirubin, or the lab translates it into words: none, slight, moderate or marked — for lipemia from hazy to milky to creamy, for hemolysis from pink-tinged to red to dark red. In the app the result is stored as text, as written on the form.
Reference range
The reference range is on your lab’s form. The ideal is “none”. Each lab decides from which index level a particular test is flagged or not reported; the effect depends on the analyser and the method, so one lab’s cut-offs cannot be applied to another lab’s results. A flagged result is not necessarily wrong — the vet may simply ask for a repeat sample.
Cats and dogs
In cats, as in dogs, serum is normally not yellow, so any yellow tint is a reason to measure bilirubin. Red cells of cats are rich in LDH, so hemolysis raises LDH. Withholding food for about 12 hours before the sample helps avoid lipemia unless there is a medical reason not to; lipemia in a fasted cat is itself a clue for the vet.
In dogs, too, hemolysis raises LDH (see LDH). A high potassium from hemolysis is not expected in most dog breeds, with the exception of some Asian breeds. A 12-hour fast is advised before routine chemistry unless there is a medical reason against it, for example in puppies or toy breeds.
Add a lab form — Pet Tracker Space recognises the lines, keeps the form’s units and draws each indicator over time with your lab’s reference band.
Sources
- eClinPath (Cornell University College of Veterinary Medicine). Interferences.
- eClinPath (Cornell University College of Veterinary Medicine). Interference indices.
- eClinPath (Cornell University College of Veterinary Medicine). Non-disease variables.
- eClinPath (Cornell University College of Veterinary Medicine). Lactate dehydrogenase.
- Merck Veterinary Manual, professional version. Collection and Submission of Laboratory Samples from Animals.
- Merck Veterinary Manual, professional version. Clinical Biochemistry.
This page explains what a lab value means. It is not a diagnosis and not a substitute for your veterinarian — only they can interpret results for your pet.