engleski

Plastic versus glass test tubes for coagulation assays

Background. Samples for coagulation testing have usually been taken into glass siliconised test tube. For better safety of laboratory personnel, plastic test tubes take place in everyday practice. This leads us to the question, whether this change could have an impact on coagulation testing due to exposure of coagulation proteins to the surface which might activate coagulation cascade. Methods. Samples were taken in duplicate. One in glass Becton Dickinson, and another in plastic Greiner Bio-one vacuette double layer test tube. Both containing 3.2% sodium citrate. Measurements of APTT, PT, TT and fibrinogen were performed on Siemens BCS coagulation analyzer from both samples, one after another. Results. Samples were taken from 95 patients. Passing and Bablock regression and Bland-Altman plot showed no statistically significant difference between measurements for APTT, PT and TT. Passing and Bablock regression equation for fibrinogen: y=-0.200 (CI 95%-0.200 to -0.011) +1.000 (CI 95%1.000 to 1.056)X, indicates that values are lower for 0.2g/L in plastic test tubes. With reference interval for fibrinogen of 1.8– 3.5g/L, and within subject biological variation for fibrinogen of 10.7%, this is not clinically relevant for values above the upper limit of interval. For pathologically low values this difference is clinically significant. The same conclusion was made based on Bland-Altman analysis. Conclusion. The results of this study suggest that plastic test tubes can be used instead of glass tubes. Because of lower values of fibrinogen in plastic test tubes, the clinician should be informed about such change.

Plastic test tubes; glass test tubes

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