A phlebotomist should verify that a patient has fasted for how long prior to obtaining a fasting specimen?

Choice A Reason:
The patient's condition is a critical factor as it can influence the ease of blood collection and the choice of collection site. For example, a dehydrated patient may have less accessible veins. Patient age is also important; pediatric and geriatric patients may require different approaches due to vein size and fragility. The blood volume required for testing must be considered to ensure sufficient sample size without compromising patient safety, adhering to guidelines that limit blood collection to a certain percentage of the patient's total blood volume.

Choice B Reason:
While patient height and gender may influence the choice of blood collection site, they are not as critical as the factors listed in choice A. Patient medications are important to consider, as some medications may affect coagulation or the integrity of the sample.

Choice C Reason:
The ordering physician's preferences may be considered, but they are not a primary factor in the method of collection. The number of tests ordered and the diagnosis can influence the volume of blood needed but are secondary to the patient's condition and safety considerations.

Choice D Reason:
The time of day and the timing of the specimen collection can be important for certain tests that are time-sensitive or influenced by diurnal variations. The test status, whether routine or stat, may affect the urgency of collection but not necessarily the method of collection.

Choice A reason:
The light green tube typically contains lithium heparin and is used for plasma determinations in chemistry. It is not suitable for coagulation studies, such as PT, because heparin is an anticoagulant that would interfere with the test results.

Choice B reason:
The lavender tube contains EDTA, which is an anticoagulant that binds calcium. While it is commonly used for complete blood counts (CBC) and other hematology tests, it is not appropriate for coagulation studies because the binding of calcium would affect the clotting process required for a PT test.

Choice C reason:
The royal blue tube can come with different additives or be additive-free, depending on the color of the closure. It is primarily used for trace element testing, toxicology, and nutrient determinations. The additives in a royal blue tube could potentially contaminate the sample and interfere with the PT test.

Choice D reason:
The light blue tube contains sodium citrate, which is the appropriate anticoagulant for coagulation studies like PT. Sodium citrate works by binding calcium in the blood, preventing clotting. The PT test measures the time it takes for a clot to form after re-calcification, making the light blue tube the correct choice for this test.