Samples & tubes

• Use the correct tube size and fill to the manufacturer's recommended volume. Gently invert immediately; do not shake.
• Prepare fresh air-dried blood smears at collection, before storage changes morphology.
• Check for clots. Refrigerate whole blood if delayed; keep slides dry at room temperature. Follow the receiving laboratory's transport instructions.

Before you send: Clots invalidate cell counts. Excess EDTA in an underfilled tube can alter cell size. EDTA is not appropriate for every species or test; check avian and exotic protocols.

• Allow complete clot formation according to the tube instructions before centrifugation.
• Separate serum promptly from cells into a clean labelled tube when required.
• Confirm that gel and clot activators are accepted for the requested assay; specialized hormone and drug tests may require different handling.

Before you send: Do not assume every chemistry or hormone test accepts serum or gel. Delayed separation changes glucose and other analytes; hemolysis, lipemia and icterus can interfere.

• Confirm the cartridge or laboratory accepts heparin plasma and the specific heparin salt.
• Fill correctly and gently invert immediately, then centrifuge and separate promptly.
• Use analyzer-specific instructions for whole-blood cartridges. Some tests need a dedicated specimen.

Before you send: EDTA contamination can falsely increase potassium and decrease calcium. Lithium heparin is unsuitable for lithium measurement; heparin is not a substitute for citrate in coagulation testing.

• Fill exactly to the mark to obtain 9 parts blood to 1 part citrate. Gently invert immediately.
• Use a clean, atraumatic collection and inspect for clots. For a winged collection set, follow the lab's discard-tube instructions to fill the tubing first.
• Contact the laboratory if hematocrit exceeds 55%, since citrate adjustment may be required. Follow its processing, freezing and shipping protocol.

Before you send: Underfilling leaves excess citrate and can falsely prolong clotting times. Never top up a tube or transfer blood from another additive tube.

• Prompt separation of serum or plasma from cells is important for accurate glucose.
• Use a glucose-preservation tube only when accepted by the laboratory; fluoride alone does not stop early glycolysis immediately.
• Record collection and processing times. Follow assay-specific storage instructions.

Before you send: A gray tube is not a general chemistry tube. Its additives can interfere with other assays; do not rely on fluoride to rescue prolonged unseparated storage.

• Label collection method and time. Cystocentesis is often preferred for culture when clinically appropriate.
• Examine promptly for specific gravity, dipstick and sediment. If delayed, refrigerate according to the laboratory protocol.
• Allow chilled urine to reach room temperature and mix before analysis. Submit a separate sterile aliquot for culture; use preservatives only if the lab requests them.

Before you send: Do not place urine in EDTA or formalin for routine urinalysis. Storage and cooling can create crystals, including struvite; crystalluria alone does not prove stones or infection.

• Allocate an appropriately sized EDTA aliquot for cytology and cell counts; gently mix.
• Prepare direct smears promptly. Keep air-dried slides dry and transport fluid as the laboratory directs.
• Collect a separate sterile plain aliquot for culture and laboratory-approved fluid chemistry. Record site and collection time.

Before you send: EDTA is not the culture container and can affect fluid chemistry. Low-volume samples need correctly sized tubes; contact the lab before dividing a scarce specimen.

• Spread material gently without crushing cells; air-dry promptly.
• Label each slide with patient details and sample site in the clinical workflow. Submit unstained slides when requested.
• Keep slides at room temperature, protected from moisture and breakage, and package separately from formalin containers.

Before you send: Formalin fumes can ruin cytology staining even without direct contact. Histology tissue is different and usually requires formalin under the receiving lab's instructions.