The process of laboratory testing requires an organized workflow to ensure patients receive accurate and timely medical care. A system of prioritization dictates which samples must be processed first. This hierarchy minimizes delays in diagnosis and treatment, particularly for time-sensitive or life-threatening conditions. The patient’s clinical status or the physical stability of the sample determines its place in the processing queue.
Establishing Specimen Priority Levels
Laboratory specimens are categorized into distinct priority levels: Routine, Urgent, and STAT. Each level is linked to a maximum allowable Turnaround Time (TAT) for results. Routine samples are for standard check-ups or monitoring chronic conditions and are processed during the normal daily workflow. Urgent samples require a faster response than routine, typically needing results within a few hours to guide timely interventions.
The highest priority samples are designated as STAT, derived from the Latin word statim, meaning immediately. A STAT order bypasses the standard queue, requiring the laboratory to stop routine work and focus on this specimen first. This immediate processing is driven by the potential for a life-saving decision. The time frame for a STAT result is typically set at one hour or less from the moment the test is ordered.
Critical Samples Requiring STAT Processing
Certain specimens are immediately labeled STAT because the results relate directly to a patient experiencing a life-threatening event. These tests provide rapid information to guide immediate medical interventions in emergency departments or intensive care units.
An Arterial Blood Gas (ABG) is a prime example, providing a rapid assessment of a patient’s respiratory and metabolic status, including oxygenation and pH balance. Delaying an ABG result could hinder immediate ventilator adjustments or treatment for severe acidosis.
Tests for cardiac markers, such as Troponin, are prioritized as STAT when a heart attack is suspected. Measuring these protein levels quickly confirms or rules out myocardial injury, allowing physicians to start time-sensitive therapies. Similarly, critical electrolyte panels (Basic Metabolic Panel) are run STAT because severe imbalances in potassium, sodium, or glucose can cause cardiac arrest or seizures.
Time-Sensitive Specimens and Stability Concerns
Time-sensitive specimens must be processed before routine work, not due to a crisis, but because their chemical components are highly unstable. Prioritizing these samples maintains the accuracy of the result. Coagulation tests, such as Prothrombin Time (PT) and Activated Partial Thromboplastin Time (aPTT), clearly demonstrate this instability.
For coagulation tests, blood plasma must be separated from blood cells within a strict timeframe to prevent the degradation of clotting factors. For instance, aPTT specimens from patients receiving heparin should have the plasma separated within one hour of collection. Delayed separation causes the integrity of coagulation factors to decline, leading to an inaccurate assessment of the patient’s bleeding or clotting risk.
Other analytes, like blood Ammonia and Lactate, require special handling to counteract ongoing metabolic processes within the collected sample. Ammonia levels increase rapidly as blood cells continue their metabolism outside the body, so the specimen must be chilled immediately with an ice slurry and processed quickly. Similarly, blood cultures, used to detect bacteria in the bloodstream, must be loaded into the automated incubation system immediately upon arrival in the lab. A delay in loading blood cultures can reduce the likelihood of detecting the causative organism and postpone specific antibiotic therapy.
Finally, certain tests contain photosensitive analytes that degrade rapidly when exposed to light. Bilirubin, frequently tested in newborns for jaundice, must be protected from light using foil or specialized amber tubes from the moment of collection. Exposure to light breaks down the bilirubin molecule, leading to a falsely low result that could mask a significant medical condition. This need for immediate, specialized handling ensures the scientific integrity of the test is preserved.