P63

Effect of rest time prior to blood sampling on common biochemical parameter - results from thyreotropin

Ida Boegh Andersen1,*, Claus Lohmann Brasen2, Lene Nohr-Jensen1, Dorthe Elkjaer Nielsen1, Jonna Skov Madsen2

1Department of clinical immunology and biochemistry, Lillebaelt Hospital, Kolding, 2Department of clinical immunology and biochemistry, Lillebaelt Hospital, Vejle, Denmark

Introduction: A variety of preanalytical parameters may have a crucial impact on the quality of laboratory results. Earlier studies have shown both exercise and positional changes prior to the blood sampling affects different biochemical parameters. However, in relation to outpatient laboratory blood sampling both hospital administrators as well as patients has expressed a wish for cutting down waiting time. Therefore the evidence whether to recommend a standardized period of rest before collection of blood samples has been challenged.

Objectives: To investigate the effect of rest time prior to blood sampling in a routine outpatient setting on common biochemical parameters – here presenting results from thyreotropin. 

Methods: Consecutive patients above the age of 20 referred to an outpatient clinic for blood sampling were included from January 2013 to December 2013. For each patient arrival time and time of blood sampling were registered electronically using Q-MATIC Suite. The impact of waiting time on thyreotropin value was analyzed using a simple linear regression. 

Results: A total of 8.712 blood samples were included in the study. The regression coefficients for individuals waiting 0-20 min, 21-40 min and 41-60 min were -0.033 (P=0.0175, n=4,546), -0.030 (P=0.0163, n=3,501) and 0.015 (P=0,3149, n=665), respectively.

Conclusion: The current pilot study shows a statistically significant effect of waiting time prior to blood sampling on thyreotropin values. Further analyses will aim to explore if this could lead to clinical misclassification. Furthermore, analysis on other biochemical parameters will be performed and based on these results decisions on whether to recommend a standardized period of rest prior to blood sampling will be taken. 

Keywords: Biochemistry, Blood, Laboratory organization