Phlebotomy technique and its impact on haemolysis in the emergency department

Background Haemolysis is a pre-analytical problem that compromises laboratory test accuracy and delays care by necessitating repeat testing. Haemolysis rates in emergency department samples are higher than those in inpatient or outpatient settings. This study evaluated the association between phlebotomy techniques and haemolysis rates in the emergency department. Methods Blood samples collected in the emergency department with documented phlebotomy technique between November 2023 and September 2024 were audited. Five phlebotomy methods were compared: [1] needle/butterfly to vacutainer (closed system), [2] syringe-needle draw, [3] syringe draw from an intravenous cannula, [4] vacutainer collection from cannula using an adapter, and [5] use of a discard tube for either needle or cannula draws. Haemolysis was defined by an Abbott Alinity H-index ≥1.25 (≈1.25 g/L free haemoglobin), above which potassium results are suppressed by the laboratory. Results Among 586 samples, 42 (7.2%) were haemolysed. Haemolysis rates were 16.7% (2/12) for syringe draw from intravenous cannula, 14.8% (31/209) for vacutainer collection from intravenous cannula using an adapter, 6.3% (1/16) for syringe-needle draw, 2.4% (2/83) for methods using a discard-tube in either needle or cannula collection, and 2.3% (6/266) for needle/butterfly to vacutainer closed phlebotomy method. Haemolysis differed significantly by method ( p < 0.0001): draws from cannula using adapter had higher rates than closed phlebotomy ( p < 0.0001) and discard-tube draws ( p = 0.0017). Conclusion Closed phlebotomy methods, particularly needle or butterfly collection into vacutainer tubes, were associated with the lowest haemolysis rates. Discard-tube samples also had low haemolysis rates, although their effect remains uncertain.