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A laboratory on the trail of troubling TSH results

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Anne Ford

September 2014—It would be a nightmare for any laboratory professional: a misdiagnosed and mistreated patient owing to an aberrant test result.

Julia C. Drees, PhD, a scientific director for chemistry at TPMG Regional Reference Laboratory, Kaiser Permanente Northern California, found herself facing that situation two years ago. She and colleague Judy Stone, PhD, then a Kaiser scientific director who is now at UCSD, discovered that faulty TSH results from their laboratory had led to multiple patients being misdiagnosed, and some even treated inappropriately. And yes—as she told the audience in a talk at the American Association for Clinical Chemistry annual meeting in July—the clinical effects were significant.

For example, “one patient was a 19-year-old young woman who was a hypochondriac and suffered from depression, and the last thing she needs is for the doctor to say, ‘Oh, there’s something wrong with your thyroid,’ give her medication and make her even sicker, even more tired, even less likely to get out of bed in the morning,” Dr. Drees said in her talk, titled “Falsely Undetectable TSH in a Cohort of Euthyroid Patients.” “It was really unfortunate.”

Even more unfortunate, Dr. Drees knew, was that if she and her colleagues didn’t get to the bottom of the TSH mystery, still more patients could be affected. “We were really baffled about what might be going on,” she said. “We wanted to know: Are there other patients at risk, and can the lab help in this situation?”

Simple questions, but answering them required a months-long investigation. In the end, that intense work paid off, not only because Dr. Drees and her team were able to solve the mystery of the faulty results, but also because the strategies they employed along the way expanded their ability to reduce patient risk from aberrant results in general. They hope their investigation, the results of which were published in April, will benefit other institutions whose patients might be at risk (Drees JC, et al. J Clin Endocrinol Metab. 2014;99[4]: 1171–1179).

The quest began in 2012, when an endocrinologist colleague of Dr. Drees contacted the laboratory to report something troubling. One of her patients—a woman later determined to be clinically euthyroid— had had her TSH levels tested with the laboratory’s normal screening assay, Siemens’ Advia Centaur TSH-3 Ultra (also known as the TSH3-UL), five times over a nine-month period. The patient’s TSH was consistently undetectable despite treatment with methimazole, an antithyroid drug. But when the endocrinologist ordered an alternative test, the Abbott Architect TSH assay, the result was >75 µIU/mL. Hindsight revealed that the methimazole had made the patient transiently hypothyroid. The drug was discontinued and the patient’s hypothyroidism resolved quickly.

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