What is the advantage of collecting STAT chemistries in a green top tube

Laboratory tube collection is a process applied when withdrawing blood samples from patients before they get tested in the laboratory. It follows the principle, which is most commonly known as the "order of draw." Different tests and biochemical assays require varying types of sample collection tubes. The reason why tubes are color-coded is for practical and easy identification.

In-vitro analysis of blood samples can be performed in clinical laboratories. However, these blood samples come in different forms. Testing procedures can require any of the following blood sample types: serum or plasma. In performing multiple collections of venous and/or arterial blood samples in a single patient, a color sequence of withdrawing and its indications based on the Clinical & Laboratory Standards Institute (CLSI) is the recommended procedure.[1]

Yellow, Pink, and Blue

These colors indicate the color of the culture bottles necessary for blood culture. These tubes (bottles) contain sodium polyanethole sulfonate (SPS), which serves as an anticoagulant. The primary function of this anticoagulant is to inhibit the activation of complement function.[2] Following the collection of the blood, mixing the bottle 8 to 10 times is needed to mix the contents adequately. The color of blood culture bottles may vary depending on the manufacturer.

Light Blue

The "citrate tube" is for collecting blood for performing coagulation studies. It contains 3.2% sodium citrate as its anticoagulant.[3] Mixing the blood inside the tube a few times is also recommended to form the plasma.

Red

There is no anticoagulant or additive inside the tube. Because of the contact of blood with the surface of the tube, the coagulation cascade becomes activated. Blood is allowed to clot for 10 to 15 minutes before subjecting to centrifugation to separate the clot from the serum further. Clotting time differs between specimens and may range from 10 minutes to almost an hour (60 minutes).

Green

The green tubes contain heparin (can either be in the form of sodium heparin, lithium heparin, or ammonium heparin), which acts as an anticoagulant by inhibiting thrombin formation. Unlike red tubes, the type of blood produced in a green tube needed for testing is not serum but plasma. Green tubes are frequently used in requesting "stat" or immediate blood chemistry results for emergency cases.

Lavender

The lavender tube is also referred to as EDTA tubes because it uses ethylene-diamine-tetra-acetic acid. The primary role of EDTA in anticoagulation is by chelating calcium ions in the blood to prevent it from coagulation. Since the blood did not clot, the liquid portion (without the red cell) is a plasma. Lavender tubes are commonly used in collecting blood samples for hematologic assays.[4]

Grey

The grey tubes contain potassium oxalate that binds to calcium, thus, inhibiting coagulation. Another substance, sodium fluoride, is also contained in the tubes, which serve as an antiglycolytic agent.[5] That is why it is used for plasma glucose and lactic acid testing.

Apart from these more commonly used collection tubes, other colored tubes (gold, tiger, pink, gold, etc.) are also used in actual hospital and clinical practice. The use of these tubes and the order of draw vary among medical institutions.[6] Tubes with anticoagulants require adequate mixing with blood. Thus, the evacuated tubes can be inverted and follow a pattern of "figure-of-8". However, proper caution must be in mind when mixing tubes as overmixing can produce hemolysis. Inefficient mixing can result in forming small clots.[7] Improper laboratory tube collection can cause harm not only in the laboratory but more so in the clinical setting.

In general, serum samples (red top tubes) are preferred for chemistry testing. This is because our chemistry reference intervals are based on serum not plasma. In general, there is little difference between serum and plasma, except for certain analytes. For example, LDH, potassium and phosphate are higher in serum than plasma, because of release of these constituents from cells during clotting. Protein and globulins are higher in plasma than serum, because plasma contains fibrinogen. The disadvantage with serum is that the samples can take a while to clot, therefore for late afternoon samples (after 3 pm Monday to Friday, after 12 pm Saturday), collection into heparin (green top tube) is advised to expedite sample handling. All stats for chemistry should be submitted in heparin so that we do not have to wait for the blood to clot. Citrate (blue top) and EDTA (lavender top) cannot be used for chemistry panels because they chelate minerals (e.g. calcium) and interfere with the tests. Furthermore, citrate dilutes the sample.

We recommend that from an individual patient, samples for chemistry should always be collected into the same tube (heparin or red top) for the duration of the patient's stay in hospital. This will ensure that changes in analytes are patient- or disease- and not anticoagulant-related. For example, if the first chemistry panel is submitted in heparin, all subsequent chemistry tests should be submitted in heparin to allow more valid comparison between sequential results.

Chemistry Test Submission Guidelines

• A full clot tube should be submitted whenever possible. Heparin tubes should always be more than half full. Underfilling of heparin will artefactually increase total bilirubin values. By providing us with as much blood as possible, we can perform additional tests as required, e.g. sample dilution etc. If we do not have enough blood, we cannot perform all the required tests. If you know that you did not collect enough blood (we need at least 1 ml of serum), you will need to prioritise which tests you want run, otherwise the important tests or tests you want may be QNS (quantity insufficient).
• For heparinized samples (especially Microtainer® tubes), ensure that the blood is mixed promptly with the heparin to avoid sample clotting. This should be done by rolling it between your palms or gentle inversion several times. Do not shake the tube!!
• Microtainer® tubes should be avoided. However, if only a small amount of blood can be collected, e.g. from a young dog or cat, or very sick animals in which multiple, sequential samples are going to be collected, the blood should be collected into 2 heparin Microtainer® tubes. These should be full (approximately 600 µL of blood/tube). We need at least 2 Microtainer® tubes to perform all our chemistry panels. 1 Microtainer® tube is acceptable if only performing a few tests, e.g. creatinine only. Red top Microtainer® tubes are not acceptable under any circumstances. Do not label Microtainer® tubes with sticky adhesive tape. It sticks to our centrifuges and we cannot get the tubes out without affecting the plasma.
• The tubes should be labeled with the patient identification and owner name at the minimum. A request form with pertinent history details should be submitted concurrently with the sample, e.g. dog administered oxyglobin. If you have separated serum or plasma from cells, please inform us if the sample is separated serum or heparinized plasma.
• If there is going to be a delay between sample collection and submission, the sample should be centrifuged and the serum or plasma separated from cells.
• For ionized calcium, serum should be submitted in a plain red top tube. EDTA or citrate samples cannot be used (these anticoagulants chelate calcium). Heparinized plasma (green top tube) also results in a falsely decreased iCa, and is not recommended. The sample should be refrigerated and shipped overnight in an insulated container with freezer packs. If more than a 48 hour delay, the serum should be frozen and shipped on dry ice. For more information, see eClinPath.

Mailed in samples or samples collected after hours

When there is going to be a delay between sample collection and submission, e.g. samples shipped to the laboratory or collected after hours, always separate serum or plasma from cells. This also applies to corvac (serum separator tubes). Constituents, e.g. AST, potassium, leak from cells with storage and will result in artefactually high values, complicating result interpretation. Furthermore, cells utilize glucose, resulting in low concentrations of this analyte with storage. This will also happen in unseparated samples collected into corvac tubes. Most analytes are stable for up to 48 hours if kept refrigerated, therefore refrigerate and mail in on a cool pack.

Which tube would be best for collecting a specimen for stat test that must be performed on serum?

Which tube would typically be used to collect plasma for a stat chemistry specimen?

Which tests require the use of a collection tube with a green stopper?

Which tests would be drawn in a green top tube quizlet?