A culture and sensitivity test is sent to which of the following divisions of a clinical laboratory?

Choice A reason:
The order of citrate, heparin, EDTA, and fluoride is not the correct sequence for blood collection. The correct order is essential to prevent cross-contamination of additives between tubes, which could interfere with test results. Citrate tubes should be drawn first to ensure that the blood does not clot prematurely, but heparin should not follow immediately after citrate.

Choice B reason:
Citrate tubes, which contain sodium citrate, are used for coagulation tests and must be drawn first to ensure the proper blood-to-additive ratio. EDTA tubes are drawn next because EDTA binds calcium and prevents clotting, making it ideal for complete blood counts and other hematology studies. Heparin tubes, which prevent clotting by inhibiting thrombin and thromboplastin, are drawn after EDTA. Lastly, fluoride tubes, which contain a glycolysis inhibitor, are drawn to preserve glucose levels and are typically used for glucose and lactate testing.

Choice C reason:
Starting with fluoride is not recommended as it could lead to contamination of the EDTA and heparin tubes with fluoride, which could affect the results of certain tests, such as calcium determinations in heparin tubes. The order of draw is designed to minimize such risks.

Choice D reason:
This sequence is incorrect because fluoride tubes are not drawn before EDTA and heparin tubes. The presence of fluoride could potentially contaminate the subsequent tubes and alter the results of the tests that require heparin or EDTA as an anticoagulant.

In phlebotomy, following the correct order of draw is crucial. The order is established based on the type of additive in each tube and its potential to interfere with tests conducted in subsequent tubes. The standard order is: blood cultures, citrate tubes, serum tubes with or without clot activator and gel, heparin tubes with or without gel, EDTA tubes, and lastly, fluoride tubes. This sequence helps prevent cross-contamination and ensures the accuracy of laboratory results, which are critical for patient diagnosis and treatment.

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.