engleski

Frequency and nature of non-compliant samples for coagulation testing

Background Like in other areas of laboratory diagnostics, preanalytical phase represents the major source of errors in coagulation testing, too. The most errors in the preanalytical phase of coagulation testing are caused by inappropriate and unacceptable samples. Aim The aim of this study was to evaluate the frequency and nature of sample non-conformities for coagulation testing during a period of 1 year (from January 2013 to December 2013). Methods As our laboratory is accredited in accordance with ISO 15189 standard for years, we routinely and continuously record all non- compliant samples for coagulation testing. All sample non- conformities are classified into the following categories: clotted sample, inappropriate ratio of anticoagulant to blood (underfilled sample), hemolyzed sample, insufficient sample quantity for all requested tests, missing sample, lipemic sample, improperly labeled sample (mislabeled or unlabeled) and sample contaminated with heparin. We evaluated the frequency of individual categories of non-compliant samples mentioned above during the overall study period of one year. Results A total of 62275 patient protocols for coagulation testing were received at our laboratory during a period of 1 year and a total of 848 samples or 1.4% (848/62275) were recorded as non-compliant. Among all non- compliant samples, clotted specimen was the most common cause for the rejection (381/848 ; 44.9%), followed by an inappropriate blood to anticoagulant ratio (205/848 ; 24.2%). The frequencies of other sample non-conformities were as follows: severe hemolyzed samples (hemoglobin>2 g/L) innapropriate for corrective action by measuring global tests (PT ; APTT ; TT ; fibrinogen) at alternative higher wavelenght (570nm) or even slightly hemolyzed samples for all other tests (115/848 ; 13.6%), missing samples (68/848 ; 8%), insufficient sample quantity (30/848 ; 3.5%), samples contaminated with heparin (29/848 ; 3.4%), lipemic samples innapropriate for measuring global tests at alternative wavelenght (11/848 ; 1.3%) and mislabeled or unlabeled samples (9/848 ; 1.1%). No significant differences in the ratio of individual categories of sample non- conformities were found between the observational 12 months (P=0.443) and clotted sample was found to be a leading cause of sample non-conformity in all 12 months (P<0.001). Conclusion The present study confirmed the relative frequency of sample non- conformities for coagulation testing to be 1.4%, a rate that is congruous to that previously reported in the literature. Clotted sample was the most common cause of sample non-conformities for coagulation analysis. Although hemolysis is usually recorded as the leading cause of unsuitable samples for coagulation testing, it was not the case in our study. We assume that it is because we routinely use as a corrective action alternative measurement of global coagulation tests at higher wavelenght for slightly and moderately (hemoglobin up to 2 g/L) hemolytic samples which significantly reduced the rate of hemolytic samples as non- compliant. Since coagulation assays are extremely sensitive to different preanalytical variables that mostly include sample collection procedures, good knowledge and continuous documentation of these variables, as well as proper education of all persons involved in this process, including laboratory personnel and those outside the laboratory, is crucial for reducing errors and obtaining reliable results of coagulation tests.

coagulation testing; non-compliant samples; frequency of non-compliance; hemolysi

Broj sažetka: P23 ; strana 56