Direct versus indirect strategies for thyroid hormone reference intervals established in a middle-aged and elderly population on an immunoassay analyzer
Sedat Motor, Gönül Erden, Birsen Sahillioğlu 1 * , Serpil Erdoğan, Mustafa Metin Yıldırımkaya
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1 Ankara Numune Hastanesi Cebeci Merkez Laboratuvarları Ankara, Turkey
* Corresponding Author


Objectives: Establishment of reference values by direct strategy for selection of reference individuals is time-consuming and expensive for laboratories. The aim of this study was to establish reference intervals for thyrotrophin(TSH), free thyroxine (FT4), free triiodothyronine (FT3) in a middle-aged and elderly population (age range; 40-80 years) on an immunoassay analyzer using both direct and indirect strategies, and to compare the results of direct and indirect strategies.
Materials and methods: As for direct sampling strategy, healthy reference individuals were randomly selected (129 male, 131 female; age range: 40-80) by questionnaire. As for indirect sampling strategy, the results of TSH, FT3, FT4 measurements of all individuals (male, n=3060-3920; female, n=4090-4520; age range 40-80 years), were selected from laboratory information system. Reference intervals were calculated by nonparametric methods
Results: The following 95% reference intervals were determined: For direct sampling group: TSH 0.32-4.38 µIU/mL; FT4 0.75-1.32 ng/dL; FT3 1.98-3.65 pg/mL. For indirect sampling group: TSH 0.29-4.36 µIU/mL; FT4 0.71-1.37 ng/dL; FT3 1.69-3.32 pg/mL. Indirect sampling group showed a good concordance in the reference intervals for TSH and FT4 with direct sampling group.
Conclusion: Indirect sampling strategy and nonparametric method may be confidently used to evaluate the reference intervals of serum TSH and FT4 on an analyzer. We suggested the utilization of a very simple and practical way, indirect sampling strategy, for evaluating reference intervals for elderly population.


This is an open access article distributed under the Creative Commons Attribution License (CC BY 4.0) which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Article Type: Research Article

J Clin Exp Invest, 2010 - Volume 1 Issue 3, pp. 161-167

Publication date: 17 Dec 2010

Article Views: 2119

Article Downloads: 648

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