NHA Phlebotomy Certification Practice Exam

The presence of a clot is acceptable in:

1. Red stopper tubes.

2. Lavender stopper tubes.

3. Green stopper tubes.

4. Light blue stopper tubes.

The correct answer is: Red stopper tubes.

The presence of a clot is acceptable in red stopper tubes because these tubes usually contain no additives or clot activators, allowing blood to clot naturally after collection. Red stopper tubes are often used for serum testing, which requires the blood sample to coagulate so that serum can be separated from the clot during the centrifugation process. This property makes them ideal for tests that analyze components found in serum, such as certain chemistry tests and hormone levels. In contrast, lavender stopper tubes contain anticoagulants that prevent clotting and are primarily used for hematology tests, while green stopper tubes contain heparin, which also acts as an anticoagulant. The light blue stopper tubes contain sodium citrate, a substance that requires the blood to be drawn and processed in a specific manner to avoid clotting for accurate prothrombin time and activated partial thromboplastin time tests. Therefore, clots should not be present in these tubes to ensure the integrity and reliability of test results.