Validity of standard reference values irrespective of rest and time of day prior to blood sampling-results from albumin and thyrotropin

I. B. Andersen, C. L. Brasen, H. Christensen, D. E. Nielsen, I. Brandslund, Jonna Skov Madsen

Research output: Contribution to journalConference abstract in journalResearch


Background: Preanalytical factors affects different biochemical parameters. Therefore reference intervals are recommended to apply to rules of standardization that state that blood samples should be taken in the morning after 15 min rest. However, both hospital and patients have a wish to minimize waiting time prior to blood sampling. Moreover, some parameters have diurnal variation and since there is a growing desire to expand opening hours in the clinics this variation is worth investigating further. Therefore our aim is to test whether the reference intervals of albumin and thyrotropin are valid throughout the opening hours and investigate the impact of resting time. Materials and method: All patients referred to an outpatient clinic for blood sampling were included during Nov. 2011-Jun. 2014 (opening hours: 7am-3pm). For each patient arrival time and time of blood sampling were registered electronically using Q-MATIC Suite. Impact of resting time and time of day on thyreotropin and albumin values was analyzed using a simple linear regression. The "maximum allowable bias" was used as quality indicator for the reference interval. Results: Using linear regression we found significant diurnal variation and influence by resting time for albumin (n = 15,544) and thyrotropin (n = 20,019) with p-values: 0.004 (rest) and <2x10-16 (diurnal) for thyrotropin, 2.6x10-4 (rest) and <2x10-16 (diurnal) for albumin. For albumin the maximum allowable bias never exceeded limits for accepting reference values for any resting time or time of day (but was on limit at 3pm). Thyrotropin concentration decreased from 7-9am. After 9am the change exceeded maximum allowable bias. For the resting no pattern was observed. Conclusion: It is not necessary to wait 15 min prior to blood sampling. Albumin may need a change of reference interval if opening hours is expanded. Thyrotropin diurnal variation is very important and change of procedure or reference interval is necessary.
Original languageEnglish
Article numberP184
JournalClinical Chemistry and Laboratory Medicine
Issue number4
Pages (from-to)eA88
Publication statusPublished - 2015
Event3rd EFLM-BD European Conference on Preanalytical Phase - Porto, Portugal
Duration: 20. Mar 201521. Mar 2015


Conference3rd EFLM-BD European Conference on Preanalytical Phase

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