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Clinical Chemistry 44: 1772-1773, 1998;
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(Clinical Chemistry. 1998;44:1772-1773.)
© 1998 American Association for Clinical Chemistry, Inc.

Letters

Daily BlankCell Procedure in Elecsys 2010 Improves the Reproducibility of Thyrotropin, Free Thyroxine, and Triiodothyronine

Miguel Angel Navarroa, Teresa Palencia, María Rosa Bonnín, and Pilar Rosel

Hormone Unit (Biochemistry Department), Ciutat Sanitária i Universitária de Bellvitge, L'Hospitalet de Llobregat, 08022 Barcelona, Spain
a Address correspondence to this author at: Moragas 12–22, 6°B, 08022 Barcelona, Spain. Fax 34 3 2630162; e-mail manavarro{at}csub.scs.es.


To the Editor:

A fully automated analyzer (Elecsys 2010®) incorporates a new generation of electrochemiluminescence immunoassays (ECLIAs) (1)(2)(3). At the core of the system is the ECL detection cell, which comprises three main parts: a magnet, a working electrode, and a photomultiplier. The streptavidin microparticles, coated with biotinylated antigen-antibody complexes, are deposited on the working electrode; the nonreactive particles, excess reagent, and sample are separated by flushing out through a buffer solution (ProCell) at pH 6.8. A voltage is then applied to the electrode, and emitted light is measured with the photomultiplier. A special cleaning solution (CleanCell) at pH 13.2 is used to wash the electrode surface; the measuring cell can then be regenerated by varying the potential on the electrode.

An optional BlankCell procedure corrects variations in the signal of the measuring cell and photomultiplier tube. This procedure uses two reagents: one is the same as that found in ProCell solution, and the second contains a defined quantity of ruthenium label. Given the stability of the signal, the manufacturer does not provide customers with protocol criteria as to when to perform this BlankCell procedure, but on the contrary, seems to recommend that it be carried out only by service personnel during the maintenance of the system.

We analyzed the effect of carrying out the BlankCell procedure daily for the measurement of thyroid hormones (thyrotropin, free thyroxine, and triiodothyronine). In April and May 1997, the assays were performed without BlankCell procedure, whereas in June 1997, the BlankCell procedure was carried out daily. We used Immunoassay Controls Comprehensive Tri-Level (Dade) to assess the imprecision (Level I, lot no. IAC1–129; Level II, lot no. IAC2–229; and Level III, lot no. IAC3–329) at the concentrations shown in Table 1 . Control Level III for triiodothyronine was discarded because the values obtained were <0.30 nmol/L.


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  		Table 1. Interassay reproducibility for three thyroid hormones studied during the months of April, May, and June.

The results for interassay reproducibility obtained in this study are shown in Table 1Up . We observed significant differences (P <0.001, F Snedecor) of CVs between those months in which we worked without a daily BlankCell (April/May) and the month (June) when it was used. CVs were almost twice as low for thyrotropin and free thyroxine in the month of June, and the imprecision was particularly noticeable for triiodothyronine, where the CVs at the same concentrations decreased threefold.

Previous studies of Elecsys (4), do not address technical aspects that might improve the routine daily work. The life of the measuring cell would seem to depend on several factors; of these, the throughput and the sample material are the most important. In these conditions, the CleanCell solution may use up the measuring cell, and therefore, it appears reasonable to check its sensitivity by the BlankCell procedure. Diagnostic potential of thyrotropin assay as a first-line thyroid function test (5)(6) may be improved with improved CVs. Although triiodothyronine is considered a second-line test in thyroid diseases, we observed high T3 in patients receiving L-thyroxine therapy, perhaps reflecting conversion of T4 to T3. This, together with use of T3 in patients with non-thyroidal illness, suggests that the CVs for this hormone should also be improved. Given that the BlankCell procedure can be conducted in 5–6 min, we believe that the users of Elecsys 2010 will find it useful to produce considerable improvements in the quality of their results. The present data do not allow us to assess the relative values of use of the procedure on a weekly or monthly vs daily schedules.


Acknowledgments

We thank Marc Gómez, product manager of Boehringer Mannheim España, for technical assistance.


References

  1. Erler K, Egger M. Electrochemiluminescence applied to heterogeneous immunoassays. J Clin Ligand Assay 1996;19(Suppl):93-99.
  2. Self CH, Cook DB. Advances in immunoassay technology. Curr Opin Biotechnol 1996;7:60-65. [ISI][Medline] [Order article via Infotrieve]
  3. Yang H, Leland JK, Yost D, Massey RJ. Electrochemiluminescence: a new diagnostic and research tool. ECL detection technology promises scientists new "yardsticks" forquantification. Bio/Technology 1994;12:193-194. [Medline] [Order article via Infotrieve]
  4. Sapin R, Gasser F, d'Herbomez M, Wemeau JL, Ebert C, Schlienger JL. Elecsys® Thyrotropin (TSH) assay evaluated. Clin Chem 1997;43:545-547. [Free Full Text]
  5. Spencer CA, Takeuchi M, Kazarosyan M. Current status and performance goals for serum thyrotropin (TSH) assays. Clin Chem 1996;42:140-145. [Abstract/Free Full Text]
  6. Squire CR, Fraser WD. Thyroid stimulating hormone measurement using a third generation immunometric assay. Ann Clin Biochem 1995;32:307-313.




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Right arrow Articles by Navarro, M. A.
Right arrow Articles by Rosel, P.
Related Collections
Right arrow General Clinical Chemistry

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