Detection of haemolysis, a frequent preanalytical problem in the serum of newborns and adults.

Background: Preanalytical problems can be more frequent in case of preterm and term newborns as compared to the general patient population. Here we present the leading preanalytical errors in our laboratory, the prevalence of haemolysis and its impact on laboratory test results, and our efforts to improve the diagnostic workup of newborns' samples.

Methods: Preanalytical quality indicators were analysed in all samples in 2018. The haemolysis index was measured spectrophotometrically in serum samples in the period of 2012-2018, and the ratio of haemolysed samples and the test rejection rates were analysed. The data of newborns and other patients were analysed separately.

Results: During the tested year, the leading preanalytical errors were haemolysis in serum samples, inadequate sample identification and clotting of anticoagulated blood regarding all samples or newborns. In this seven-year period the ratio of haemolysed serum samples was 4.00% in all patients and 46.4% in newborns, while the test rejection rates due to haemolysis were 0.57% and 3.71%, respectively. Haemolysis indices were significantly higher in case of newborns than in patients with documented severe intravascular haemolysis which suggests that the major reason of elevated haemolysis indices in newborns was in vitro haemolysis. Accordingly, all C-reactive protein (CRP) results which were rejected by severe haemolysis became reliable after repeating blood sampling.

Conclusion: Haemolysis is the leading preanalytical problem not only in newborns but also in the general patient population. Our study highlights the importance of automated assessment of serum indices and continuous monitoring of the preanalytical quality indicators and suggests the need for education and blood collection trainings.