PB1166 - The true effect of haemolysis interference on routine coagulation tests using paired matched samples performed on the Sysmex CN-series coagulation analyser

Background: Haemolysis interference with coagulation tests is dependent on the reagents, detection systems, and through the biological activation of the haemostasis cascade. Paired matched haemolysed/non-haemolysed samples facilitate the true assessment of haemolysis interference. This is required to ensure validity and reliability of patient results.

Aims: This study assessed haemolysis interference on PT, APTT, Fibrinogen, D-Dimer and Thrombin Time (TT), using Siemens/Hyphen reagents on the Sysmex CN-6000.

Methods: Haemolysed trisodium citrate samples were identified using the Sysmex CS-5100 haemolysis index. If a repeat sample was received within 4 hours of collection of the haemolysed sample, residual plasma from both samples was aliquoted and frozen (-80°C). Paired matched samples were processed on the Sysmex XN-10 for haemoglobin quantitation (Hb), and haemostasis assays on the CN-6000. A reference range (RR) was established with 30 normal samples for PT, APTT, Fibrinogen, and TT. For D-Dimer, 0.5 mg/L exclusion cut-off was utilised, and for PT INR, a 2.0 – 3.0 therapeutic range.

Results: Large variance in minimum and maximum differences between haemolysed and non-haemolysed samples for all assays was observed (Table 1). PT/APTT/TT displayed shorter clotting times when haemolysed, most pronounced in APTT, but also prolonged in a small subset. Variability between reagents was observed. At the upper RR limit in haemolysed samples, Fibrinogen was either increased/decreased, but no difference was observed at the lower RR limit. False positive/negative D-Dimer results were observed in haemolysed samples compared to non-haemolysed samples. No correlation between Hb and observed differences were noted (Table 2).

Conclusion(s): Haemolysis interference appeared variable, with decreased and increased clotting times/concentrations, irrespective of Hb. Interpretation with RRs demonstrated that haemolysis may influence patient diagnosis/treatment, most significantly for APTT, and less significantly for PT, Fibrinogen, D-Dimer, and TT. Haemolysed samples for APTT should be rejected since the lowest levels of Hb can significantly impact measured values.