engleski

Impact of plasma bilirubin on hemolysis index value

Background: Hemolysis is the most common pre-analytical interference and it often causes blood sample rejection. A new generation of laboratory analyzers can report cell-free hemoglobin qualitatively or semi-quantitatively as hemolysis index (HI). Every manufacturer of reagents specifies the HI at which analysis is permitted. As bilirubin can affect free-hemoglobin measurement and consequently HI, impact of plasma bilirubin on HI value was evaluated in emergency laboratory as part of laboratory method verification. Materials and methods: 49 samples were prepared by mixing hemoglobin-free low-bilirubin plasma pool (blank pool), hemolysate and bilirubin enriched pool to get different degrees of HI (0 – 115) and bilirubin concentrations (5.4 – 436.7 μmol/L). The HI and bilirubin concentrations were measured in triplicate on Roche Cobas ce6000 analyzer. Results of HI measurements were evaluated and presented as absolute differences from blank pool. Statistical analysis was performed using Wilcoxon rank-sum test. Results: For samples with bilirubin concentrations 37.2, 55.1, 82.2 and 188.6 μmol/L, absolute difference in measured HI was ≤ 2 and no statistically significant difference in HI value was observed (P>0.05). There was statistically significant difference in HI value for samples with bilirubin concentrations of 276.8 μmol/L (P=0.0312) and 436.7 μmol/L (P=0.0156). The absolute differences in measured HI were 0 – 11 leading to decrease of HI values and were greater as bilirubin concentration was higher. Conclusions: The use of new technology for detection and measurement of common interferences can aid in detecting improper samples received in laboratory and furthermore, in minimizing erroneous clinical decisions based on laboratory test results. This study shows that high bilirubin can cause false decrease in HI values and thus the samples, that are usually rejected, can be wrongly accepted. To avoid errors and promote continuous quality improvement of laboratory service, further examination of pre-analytical interferences should be of high interest.

hemolysis ; hemolysis index ; bilirubin ; interference

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