Influence of hemolysis on routine clinical chemistry testing.
BACKGROUND
Preanalytical factors are the main source of variation in clinical chemistry testing and among the major determinants of preanalytical variability, sample hemolysis can exert a strong influence on result reliability. Hemolytic samples are a rather common and unfavorable occurrence in laboratory practice, as they are often considered unsuitable for routine testing due to biological and analytical interference. However, definitive indications on the analytical and clinical management of hemolyzed specimens are currently lacking. Therefore, the present investigation evaluated the influence of in vitro blood cell lysis on routine clinical chemistry testing.


METHODS
Nine aliquots, prepared by serial dilutions of homologous hemolyzed samples collected from 12 different subjects and containing a final concentration of serum hemoglobin ranging from 0 to 20.6 g/L, were tested for the most common clinical chemistry analytes. Lysis was achieved by subjecting whole blood to an overnight freeze-thaw cycle.


RESULTS
Hemolysis interference appeared to be approximately linearly dependent on the final concentration of blood-cell lysate in the specimen. This generated a consistent trend towards overestimation of alanine aminotransferase (ALT), aspartate aminotransferase (AST), creatinine, creatine kinase (CK), iron, lactate dehydrogenase (LDH), lipase, magnesium, phosphorus, potassium and urea, whereas mean values of albumin, alkaline phosphatase (ALP), chloride, gamma-glutamyltransferase (GGT), glucose and sodium were substantially decreased. Clinically meaningful variations of AST, chloride, LDH, potassium and sodium were observed in specimens displaying mild or almost undetectable hemolysis by visual inspection (serum hemoglobin < 0.6 g/L). The rather heterogeneous and unpredictable response to hemolysis observed for several parameters prevented the adoption of reliable statistic corrective measures for results on the basis of the degree of hemolysis.


CONCLUSIONS
If hemolysis and blood cell lysis result from an in vitro cause, we suggest that the most convenient corrective solution might be quantification of free hemoglobin, alerting the clinicians and sample recollection.
Lippi
Giuseppe
G
Istituto di Chimica e Microscopia Clinica, Dipartimento di Scienze Morfologico-Biomediche, Università degli Studi di Verona, Verona, Italy. ulippi@tin.it
Salvagno
Gian Luca
GL
Montagnana
Martina
M
Brocco
Giorgio
G
Guidi
Gian Cesare
GC
D016477:Artifacts; D001322:Autoanalysis; D001772:Blood Cell Count; D001774:Blood Chemical Analysis / Q000379:methods* / Q000592:standards; D001798:Blood Proteins / Q000032:analysis; D002624:Chemistry, Clinical / Q000379:methods* / Q000592:standards; D019411:Clinical Laboratory Techniques / Q000379:methods* / Q000592:standards; D015925:Cryopreservation; D004573:Electrolytes / Q000097:blood; D004798:Enzymes / Q000097:blood; D005615:Freezing; D005947:Glucose / Q000032:analysis; D006454:Hemoglobins / Q000032:analysis; D006461:Hemolysis / Q000502:physiology*; D006801:Humans; D007201:Indicator Dilution Techniques; D015203:Reproducibility of Results
D001798:Blood Proteins; D004573:Electrolytes; D004798:Enzymes; D006454:Hemoglobins; D005947:Glucose