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Clinical Chemistry 43: 1097a-1098a, 1997;
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(Clinical Chemistry. 1997;43:1097A-1098.)
© 1997 American Association for Clinical Chemistry, Inc.

Letters

Rapid Qualitative TSH Test to Screen for Primary Hypothyroidism

Jerome M. Hershmana and Lori Berg

Endocrine Res. Lab., West Los Angeles VA Med. Center and UCLA School of Med. 11301 Wilshire Blvd. Los Angeles, CA 90073
a Author for correspondence.


To the Editor:

We evaluated a qualitative, solid-phase two-site immunochromatographic assay (ThyroChek; Franklin Diagnostics, Cedar Knolls, NJ) for identifying serum samples that contain thyrotropin (TSH) in a concentration >5 mU/L. The test is intended for use as a screening method for primary hypothyroidism. Reagents were provided to us by the manufacturer. The test is performed by adding 4 drops of serum (~0.1 mL) to the well of the cassette. The serum is adsorbed onto the nitrocellulose membrane, exposed to the mobile-phase antibody to intact TSH that is labeled with colloidal gold, and then passes through the site at which capture antibodies (anti-TSHß) are attached. The presence of TSH >5 mU/L creates a pink line that is read at 10 min after adding the sample.

We evaluated the test by using serum samples that had been assayed for TSH previously by the Abbott IMx Ultrasensitive hTSH II method. The samples were obtained with the patients' approval according to the ethical standards of our institution and had been stored frozen for up to 6 months. Our normal range for this assay is 0.4–4.0 mU/L; the within-assay and between-assay CVs are <8% (1). The samples were divided into four categories: suppressed, TSH <0.05 mU/L, n = 23; normal, TSH 0.4–4.0 mU/L, n = 41; subclinical hypothyroidism, TSH 5–10 mU/L, n = 30; and hypothyroidism, TSH >10 mU/L, n = 31. The samples were randomized, tested in groups of 5 to 10 samples, and the reader of the ThyroChek test was blinded to the clinical status and immunoassay results. The ThyroChek results for each category were (positive/negative): suppressed 0/23, normal 0/41, subclinical hypothyroidism 29/1, and hypothyroid-ism 31/0. On the basis of these data, the sensitivity of the assay is 98% (60/61) and the specificity is 100% (64/64). Several samples of each category tested repeatedly (up to 4 times) gave the same result.

Samples with TSH concentrations >20 mU/L gave very intense lines that were readily seen. Samples with TSH concentrations of 5–10 mU/L gave a faint response that was more easily recognized after the experience of performing several assays. The results are shown in Fig. 1 .



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  		Figure 1. ThyroChek result compared with serum TSH by IMx measurement.

Screening for mild thyroid failure in older patients has been recommended as a cost-effective procedure (2). The ThyroChek assay appears to be useful as a qualitative screening test for primary hypothyroidism.


Acknowledgments

This work was supported by VA Medical Research Funds.


References

  1. Hershman JM, Pekary AE, Berg L, Solomon DH, Sawin CT. Serum thyrotropin and thyroid hormone levels in elderly and middle-aged euthyroid persons. J Am Geriatr Soc 1993;41:823-828. [ISI][Medline] [Order article via Infotrieve]
  2. Danese MD, Powe NR, Sawin CT, Ladenson PW. Screening for mild thyroid failure at the periodic health examination. JAMA 1996;276:285-292. [Abstract]




This Article
Right arrow Extract Freely available
Right arrow Full Text (PDF)
Right arrow Submit an electronic Letter to
the Editor about this paper
Right arrow Alert me when this article is cited
Right arrow Alert me when eLetters are posted
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in ISI Web of Science
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via ISI Web of Science (2)
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Hershman, J. M.
Right arrow Articles by Berg, L.
Right arrow Search for Related Content
PubMed
Right arrow Articles by Hershman, J. M.
Right arrow Articles by Berg, L.
Related Collections
Right arrow Evidence Based Laboratory Medicine and Test Utilization
Right arrow Endocrinology and Metabolism

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