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Patients with a history of syncope should always be placed in a supine (lying down) position before venipuncture. This prevents falls and injuries if fainting occurs during or after the draw. Standing or using a high stool increases the risk of collapse and injury, while sitting with legs crossed can restrict blood flow and contribute to fainting. ASCP emphasizes patient safety as a top priority, requiring phlebotomists to recognize risk factors, provide reassurance, and monitor the patient closely throughout the procedure.

Comprehensive and Detailed Explanation:

Coagulation studies, including PT and aPTT, require plasma preserved with sodium citrate, which binds calcium reversibly. The light blue-top tube maintains clotting factors in their inactive form until testing. EDTA and heparin irreversibly affect clotting pathways, invalidating results. Serum lacks clotting factors, making it unsuitable. Proper fill volume (9:1 blood to anticoagulant ratio) is critical for accurate testing; underfilling skews results. ASCP guidelines stress correct tube choice and fill levels for coagulation studies, as errors directly compromise patient care and treatment decisions.

Comprehensive and Detailed Explanation:

For ova and parasite (O&P) testing, stool specimens must be collected in preservative solutions such as 10% formalin or polyvinyl alcohol (PVA). These prevent degradation of parasite ova, cysts, and trophozoites, preserving morphology for microscopic identification. Fresh stool without preservative may be acceptable if examined immediately, but preserved specimens are standard. Urine, sputum, and blood cultures are not appropriate for O&P testing. ASCP highlights correct specimen collection and handling for non-blood tests to ensure diagnostic accuracy.

Prolonged tourniquet application causes hemoconcentration, where plasma water leaks into tissues while larger molecules and cells remain in the vessel. This leads to falsely elevated analytes such as proteins, calcium, and potassium. The effect can compromise the accuracy of laboratory results and cause inappropriate clinical decisions. ASCP guidelines emphasize removing the tourniquet within one minute, ideally as soon as blood begins to flow into the tube. Patient safety and specimen integrity depend on this timing. Other risks of prolonged application include petechiae, hematoma, and patient discomfort. Proper preparation—having supplies ready before applying the tourniquet—helps phlebotomists complete collections efficiently and within safety standards.

Comprehensive and Detailed Explanation:

Bilirubin degrades when exposed to light, leading to falsely low results. To prevent this, specimens must be wrapped in foil or collected in amber-colored tubes. Potassium, glucose, and sodium are stable in light. ASCP emphasizes awareness of light-sensitive analytes to ensure specimen integrity.