Requisitions, Test Priorities and Timed Draws

The Laboratory Requisition and Order Verification

A laboratory requisition is the formal order that authorizes a phlebotomist to collect a specimen from a patient. Every phlebotomy procedure begins with reviewing this document, which may exist as a paper form or an electronic record. A requisition must include the patient's name and the additional patient identifier or identifiers required by facility policy, such as a date of birth or medical record number. It must also identify the ordering healthcare provider and clearly specify the exact laboratory tests ordered. For inpatient collections, the requisition typically includes the patient's room and bed number.

In addition to basic demographic and test details, the requisition provides essential collection instructions. The phlebotomist must check the requisition or patient record for the requested collection date and, for timed tests, the required collection time. It is equally critical to review the requisition or patient record for relevant patient preparation requirements, such as fasting, and specific collection precautions, such as a latex allergy. Once the collection is completed, the collecting phlebotomist's unique identifier or initials must be recorded directly on the requisition or within the electronic health record to maintain accountability.

Requisitions also contain diagnosis codes that provide the clinical indication used by third parties and institutions to assess the medical necessity of the ordered tests. The phlebotomist is not permitted to assign, alter, or interpret diagnosis codes under any circumstances. If an order on a requisition is ambiguous, missing, or illegible, the phlebotomist must seek clarification from the ordering provider or supervisor rather than guessing. Similarly, if duplicate orders appear to be unintended, the phlebotomist must clarify them with the nurse, ordering provider, or supervisor before drawing additional blood.

Healthcare facilities enforce clear procedures regarding provider authorization. If an order lacks the required provider authorization, the phlebotomist must follow facility policy to obtain proper verification before collecting the specimen. Verbal laboratory orders must be accepted and documented only as permitted by institutional policy, which includes securing subsequent provider authentication when required. Furthermore, if a patient questions why a specific test is ordered, the phlebotomist must refer the patient to their healthcare provider; a phlebotomist must never interpret test rationales or clinical diagnoses to a patient.

Specimen Collection Priorities

Test priority establishes the order and urgency of specimen collection, transport, and laboratory processing. Establishing priorities ensures that critically ill patients receive rapid interventions while maintaining an efficient workflow for standard medical evaluations. Phlebotomists must organize their tasks to honor these priority levels while keeping scheduled collections on time.

STAT orders carry an urgent clinical need and require collection, transport, and laboratory processing as soon as possible under facility policy. Although STAT orders generally represent the highest collection urgency, they are not limited to life-threatening emergencies; providers also utilize them whenever rapid clinical decisions are mandatory. In contrast, ASAP orders indicate a collection priority higher than routine but lower than STAT. ASAP orders require prompt collection but have lower priority than STAT orders; the priority designation alone does not establish the severity of the patient's condition.

Routine orders represent non-urgent laboratory tests that are collected during standard collection schedules. These orders are commonly used for baseline monitoring, preventive care, and ongoing chronic disease management. Timed priority collections take precedence over routine specimen collections because their clinical value depends strictly on when the blood is drawn. However, even when balancing urgent demands, timed specimens must still be collected at their required times, while STAT orders maintain the highest overall urgency.

Therapeutic Drug Monitoring and Trough versus Peak Levels

Timed draws are blood collections performed at a specific, predetermined time. A primary application of timed draws is therapeutic drug monitoring, which measures medication concentrations in the bloodstream to evaluate efficacy and prevent toxicity. If a therapeutic drug monitoring specimen is collected at the wrong time, it may yield a misleading result that could adversely affect clinical dosing decisions made by the healthcare team.

Therapeutic drug monitoring may call for a trough, a peak, or both, depending on the medication and the ordered protocol. A trough level represents the lowest concentration of a medication in a patient's bloodstream. To measure the trough concentration, a trough specimen is typically collected immediately before the next scheduled dose, according to the medication-specific protocol. Conversely, a peak level represents the highest concentration of a medication in the patient's bloodstream.

The required collection time for a peak drug level depends on the specific medication, the route of administration, and the testing protocol established by the facility. For instance, medications administered intravenously reach peak concentrations more rapidly than medications given orally. Because administration schedules can change, the phlebotomist must confirm the actual medication administration time and the required collection time with nursing staff or by consulting the medication record according to facility policy before performing the draw. After collection, the phlebotomist must record the actual collection time on the specimen label and within the requisition or electronic record as required by facility policy.

Metabolic Challenges, Diurnal Variations, and Serial Collections

Certain laboratory tests require strict adherence to physiological timing, baseline dietary restrictions, or bodily rhythms. Fasting orders require the phlebotomist to confirm that the patient has abstained from food and beverages other than water for the specified duration. If an interview reveals that a patient has not met these fasting requirements, the phlebotomist must document the patient's intake, notify the nurse or supervisor, and follow facility instructions on whether to collect the specimen or reschedule the draw.

Other timed tests account for diurnal variation, which refers to normal biological fluctuations in analyte concentrations over a 24-hour period. For example, blood levels of the hormone cortisol exhibit diurnal variation, typically reaching their peak in the early morning. Collecting a cortisol specimen at the wrong hour could lead to an inaccurate assessment of the patient's endocrine function.

Metabolic challenge tests also depend entirely on precise timing. A glucose tolerance test generally includes a fasting baseline specimen followed by blood specimens collected at specified intervals after the patient drinks a standardized glucose solution. The patient must finish the glucose tolerance beverage within the time specified by the test protocol, commonly five minutes; the phlebotomist must use that protocol to determine when the timed collection interval begins. Another metabolic assessment is the postprandial glucose test, where specimens are collected at the ordered interval, commonly two hours after the start of a meal. Finally, serial timed draws, such as those ordered for cardiac troponin, are used to monitor evolving tissue injury over time through carefully spaced collections.

Patient Identification, Discrepancies, and Safe Labeling

Before any specimen is collected, positive patient identification must be established. The phlebotomist must use two approved patient identifiers and match them to the requisition or electronic order, checking the identification band when one is required, such as for an inpatient. Even though a room and bed number appear on an inpatient requisition, the phlebotomist must never use a room or bed number as an identifier.

If the patient identifiers on the order and the identification band do not agree, the phlebotomist must not collect the specimen until the discrepancy is resolved according to facility policy. Any unresolved patient-identification discrepancy must be reported to the nurse or supervisor, and the phlebotomist must follow institutional procedures to correct the error before proceeding with venipuncture.

Once blood collection is successfully completed, labeling must occur immediately in the patient's presence; tubes must never be labeled before the draw. Specimen labels must contain the required patient identifiers and collection details, and these identifiers must match the requisition or electronic order exactly. Recording the actual collection time and the phlebotomist's unique identifier or initials ensures a clear, traceable record for laboratory processing.