Question 8

Underfilling the tube can be a source of a preanalytical error when collecting a blood specimen.

When a phlebotomist underfills a blood collection tube, it can lead to inaccurate test results due to insufficient sample volume. This can affect the concentration of the analytes being tested and may result in erroneous interpretations by the laboratory.

A) Inverting the tube after collection

Inverting the tube after collection is a standard practice to ensure proper mixing of the blood with the anticoagulant or preservative present in the tube. This action is not a source of preanalytical error; rather, it is essential for obtaining accurate test results.

B) Using an 18 gauge needle

Using an 18 gauge needle is generally acceptable for blood draws, especially for larger volumes or certain tests. While a larger gauge needle may cause hemolysis in some cases, it does not directly lead to preanalytical errors associated with sample volume, making this option incorrect.

C) Tying a tourniquet loosely

Tying a tourniquet loosely may not effectively engorge the veins, potentially making it more difficult to obtain a blood sample. However, this action primarily affects the ease of collection rather than contributing to a preanalytical error regarding the integrity of the sample collected.

D) Underfilling the tube

Underfilling the tube is a significant source of preanalytical error, as it results in insufficient blood volume for accurate testing. Many laboratory tests require specific blood-to-additive ratios, and failing to meet these requirements can lead to inaccurate results.

Conclusion

Underfilling the tube is the only option that directly compromises the integrity of the blood specimen collected, leading to potential inaccuracies in test results. All other options either do not lead to preanalytical errors or are standard practices in blood collection, highlighting why D is the correct answer.