Common interferences (hemolysis from rupturing of RBCs, icterus, lipemia) and blood sample collection (e.g. too little blood into too much EDTA), handling and storage problems can affect the results of hematologic and clinical chemistry testing. A brief summary of common changes that we see is given below. The most common interferent is hemolysis (Whipple et al 2020). We have also included uncommon artifacts seen with many Heinz bodies (especially if large) and samples collected post-mortem.
|Hemolysis (rupturing of RBCs)||↓ HCT, ↓ PCV, ↓ RBC count, ↑ MCH, ↑ MCHC, ↑ platelet count, inaccurate total protein by refractometer (line difficult to read), ↑ ghost cells on blood smear||Many effects, depending on degree and method (see individual chemistry test). Some changes are: ↑ K (horses, some breeds of cattle, sheep, some breeds of dogs, pigs, camelids), ↑ AST, ↑ phosphate (with storage), ↑ iron (not always seen), ↑ TIBC, ↑ LDH, ↑ magnesium (when severe or with prolonged storage), ↑ CK, ↑ zonisamide, ↓ amylase, ↓ GGT, ↓ ALP||Artifact of sample collection or handling: Gentle blood handling, minimize temperature extremes, clean venipuncture
Endogenous interferent: Animals with an intravascular component to a hemolytic anemia
|Lipemia||↑ Hgb, ↑ MCH, ↑ MCHC, possible ↑ platelet count, ↑ total protein by refractometer, promotes in vitro hemolysis, distorts RBC morphology||Variable effect depending on degree and method (see individual chemistry tests). Some changes are: ↓ Na, ↓ Cl, ↓ bicarbonate, ↓ LDH, ↑ magnesium, ↑ TIBC||Artifact of sample collection: Collect fasting sample
Endogenous interferent (disease-related): e.g. Pancreatitis in dogs
Can high speed centrifuge the sample to decrease lipid interference
|Icterus||None||Variable, depending on degree and method (see individual chemistry test) Some changes are: ↓ creatinine, ↓ cholesterol, ↓ GGT||Endogenous interferent with hemolytic anemia or liver disease|
|↑ Hgb,↑ MCH, ↑ MCHC, possible ↑ WBC (ADVIA and Sysmex analyzers, basophil channel), ↓ reticulocytes (ADVIA), ↑ reticulocytes/platelets (Sysmex)||None||Endogenous interferent with oxidant injury: e.g. diabetic ketoacidosis in cats, acetaminophen toxicity|
|Storage||↑ MCV, ↑ HCT, ↓ MCHC, ↓ WBC, inaccurate differential cell count from leukocyte swelling (false left shift), apoptosis and false toxic change, ↓ platelet count, ↑ MPV, echinocyte formation, in vitro hemolysis||Variable, depending on test and if separated from cells. Some enzymes are unstable with storage, e.g. SDH will decrease; if not separated from cells: ↑ K (see species above for hemolysis due to leakage from cells), ↑ Ph, ↑ Mg, ↓ glucose||Store at 4°C and submit ASAP to laboratory, separate serum/plasma from cells, make fresh blood smears for hemograms (does not eliminate changes in MCV, HCT, MCHC, WBC, platelet count, MPV; just allows more accurate blood smear examination, e.g. differential leukocyte count)|
|Excess EDTA||↓ MCV, ↑ MCHC, ↓ HCT, echinocyte formation||Contamination: ↓ calcium, ↓ iron, ↑ K, ↑ TIBC, ↓ enzyme activity (e.g. ALP)||Fill blood tube to correct volume, don’t contaminate chemistry samples with EDTA (collect red or green top first)|
|Bromide treatment||None||↑ chloride (zonisamide can also do this)||Inform the laboratory that animal is on bromide therapy (we can use a method that reduces this false increase)|
|Post-mortem samples (uncommon)||Lysis of cells, bacterial contamination||Increases are seen in many test results, particularly those found in high concentrations within cells. Examples include: ↑ K, ↑ calcium, ↑ AST, ↑ LDH, ↑ Mg, ↑ Ph, ↑ iron, ↑ CK, ↓ bicarbonate. For hematologic testing, the changes under hemolysis will apply, although leukocytes and platelets will also lyse after death.||Don’t collect post-mortem samples (ocular fluid is an exception)|
* See also interferences and interference indices.