Pneumatic Tube System Versus Personnel Transport and the Hemolysis Index of Emergency Department Blood Samples: A Randomized, Split-Sample, Single-Blind Trial

Overview

Hemolysis is the most common pre-analytical error in emergency department (ED) laboratory specimens and can lead to false elevation of intracellular analytes (potassium, LDH, AST, hemoglobin), resulting in misdiagnosis and unnecessary testing. Blood samples in the ED are transported to the laboratory either by pneumatic tube systems (PTS) or manually by personnel. Although PTS shortens turnaround time, the forces generated during transport may damage erythrocyte membranes and promote hemolysis. Evidence on whether PTS increases hemolysis compared with personnel transport is inconsistent, partly because existing studies use parallel-group designs that cannot control for between-subject biological variability, and partly because findings differ across PTS brands and configurations. The Sumetzberger Power Control PTS installed at Marmara University Pendik Training and Research Hospital (speed 4-5 m/s, 120 m, cushioned capsule) has not been prospectively validated for hemolysis risk. This study uses a randomized, split-sample (within-patient matched), single-blind design in which two simultaneously drawn yellow-cap tubes from the same patient are randomly allocated, one to PTS and one to personnel transport, thereby eliminating between-patient variability. The primary outcome is the Hemolysis Index (HI) category (ordinal scale 0-5 corresponding to free hemoglobin thresholds of \<50, 50-99, 100-199, 200-299, 300-500, and \>500 mg/dL). Secondary outcomes include the rate of clinically significant hemolysis (HI \>= 1 / free Hb \>= 50 mg/dL) and the correlation between transport time and HI.

PNEUMATIC TUBE SYSTEM TECHNICAL SPECIFICATIONS The installed pneumatic tube system is a Sumetzberger Power Control system (Sumetzberger, Austria). The transit line length between the Emergency Department phlebotomy station and the central clinical laboratory is approximately 120 meters. System operating speed is set at 4-5 m/s. Transport capsules are cushioned with internal foam padding to minimize mechanical impact forces. Average transit duration ranges between 50 and 90 seconds. BLOOD COLLECTION PROTOCOL Blood collection is performed by trained emergency department phlebotomists using standard venipuncture technique. Tubes are drawn from a single venipuncture in the standard order of draw: (1) blue-cap coagulation tube, not used in the study; (2) yellow-cap serum separator tube #1; (3) yellow-cap serum separator tube #2; (4-5) any additional clinically indicated tubes, not used in the study. The two yellow-cap serum separator tubes are dispatched simultaneously by the two transport routes and are analysed simultaneously on arrival at the laboratory, so that waiting time does not act as a pre-analytical variable. RANDOMIZATION AND ALLOCATION CONCEALMENT (CONSORT 2025 Items 15-17) Allocation is by computer-generated block randomization with a block size of four. The allocation sequence assigns each participant to Sequence A (tube #1 to the pneumatic tube system, tube #2 to personnel transport) or Sequence B (tube #1 to personnel transport, tube #2 to the pneumatic tube system). The sequence is held in sealed, opaque, sequentially numbered envelopes that are opened in order at the time of enrolment. This scheme balances any effect of tube draw order across the two transport routes. BLINDING (CONSORT 2025 Item 12b) Tubes are labeled with standardized participant study identifiers and tube sequence numbers (Tube #1 and Tube #2) without indicating transport allocation. Laboratory technicians operating the automated analyzer and assessing the Hemolysis Index remain fully blinded to transport allocation. Clinicians and investigators are not blinded. WITHDRAWAL CRITERIA A participant's tube pair is withdrawn from analysis if pneumatic transport cannot be completed because of system failure, if a tube is broken or otherwise cannot be analyzed, or if the participant withdraws consent. HARMS (CONSORT 2025 Item 27) No intervention is applied to the participant. Both tubes are drawn from the venipuncture already required for routine clinical care, and no additional venipuncture or other invasive procedure is performed. No participant-level adverse events are therefore anticipated and no harms outcome measure is specified. PATIENT AND PUBLIC INVOLVEMENT (PPI) STATEMENT (CONSORT 2025 Item 8) Patients or members of the public were not involved in the design, conduct, reporting, or dissemination plans of this research. PPI was deemed non-applicable given the technical, pre-analytical nature of this laboratory quality evaluation study. DATA SHARING STATEMENT (CONSORT 2025 Item 4) De-identified individual participant data collected during the trial will be made available upon reasonable request to the corresponding investigator following publication.