Poor positive predictive value of low sensitive thyrotropin assay levels for hyperthyroidism in nursing home...

We assessed the positive predictive value of a low thyrotropin (TSH) level on sensitive TSH (STSH) assay as an indicator of hyperthyroidism. In 742 determinations on nursing home residents who were not taking thyroid hormone, we identified 15 with low TSH levels. None of the residents had a completely suppressed (undetectable) TSH level upon initial testing or an elevated total triiodothyronine (T3) or thyroxine (T4) level. Half the patients in whom total T3 was measured had low levels. Of 11 surviving residents, four subsequently had a normal TSH level and six others had a normal free T4 level. Only one patient had a slight elevation of the free T4 level. None of the residents were diagnosed as having hyperthyroidism.