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The objective of the
following study of Massih and co-authors, Marilia, SP, Brazil,
was to evaluate the cost-effectiveness of the laboratory
diagnosis of hypothyroidism in a General Hospital. Medical
records of 126 patients with hypothyroidism (105 female, 83%; 21
male, 16%) diagnosed between 1993 to 1997 by physicians
(non-endocrinologists) were reviewed. In spite of the TSH
determination being the most important test to diagnose
hypothyroidism, they found that apart from TSH, total T4 and
total T3 were additionally frequently ordered by physicians (94
patients, 74.8%) while TSH and FT4 were ordered only for 28
patients (22.2%) and TSH alone for only four patients (3.2%).
Surprisingly, a TRH test was performed in 42 patients (33%) and
RAIU in 67 (53%), apparently to confirm the diagnosis. The cost
for the all 751 thyroid tests, including a TRH test and RAIU,
performed to diagnose thyroid gland failure in 126 patients, at
the hospital, was R$ 23,994 (about 18,000 US dollars).
Nevertheless, if only TSH and FT4 tests had been ordered, the
laboratory costs would have been R$ 5,355 (about US$ 3,600) with
a saving of R$ 18.639. Furthermore, considering all laboratory
tests performed, finally diagnosing hypothyroidism, the total
cost was R$ 34.524 (about 24,500 US dollars). Due to so many
pitfalls in diagnostic management of these hypothyroid patients,
the time spent to reach the correct diagnosis was very long,
about 51 weeks (1 to 496) and the number of out-patient visits
excessive, ranging from 1 to 36. They concluded that there are
several inadequacies in the diagnostic management of hypothyroid
patients at the hospital, mainly in the selection of diagnostic
tests and in the interpretation of the results, leading to
unnecessary expenses of the already limited resources.
Weiss and collaborators, Chicago, IL, and San Juan Capristano, CA, USA, reported on the systematic inaccuracies in serum Free T4 immunoassays related to serum T4 binding. The objective of this study was to develop a standard method, using generally available materials, for quantifying systematic inaccuracies in FT4 measurements related to variations in levels of serum T4 binding-proteins (PB). Protein-binding of T4 (PBT4) was varied while [FT4] was kept constant. Analytical recovery was determined at 12 levels of T4 binding. T4-free human serum was concentrated by ultrafiltration to achieve high serum T4 binding (23.8 µg PBT4 / 1 ng FT4). TBG-free, T4-free human serum was diluted with physiologic buffer (pH 7.4) to achieve low serum T4 binding (0.3 µg PBT4 / 1 ng FT4). T4 was added to both sera until [FT4] was 1.2 ng/dl in each as determined by direct equilibrium dialysis calibrated to gravimetric FT4 standards. Ten (10) mixtures produced intermediate levels of T4 binding. The levels obtained were similar to levels reported in native human sera including low TT4 in NTI (= non-thyroidal illness) (10th Int Cong Endocrinol 1995, Abst P2-1033) FT4 measurements in triplicate were obtained with 5 FT4 methods/commercial kitts. FT4 results produced by these methods were divided by 1.2 ng/dl to calculate % analytical recovery. RESULTS: Analytical recoveries ranged from 2% to 155% for DPC, 25% to 131% for IMs, 51% to 100% for Stratus II, 37% to 93% for AsSYM and 37% to 73% for ACS180. For each FT4, method, recoveries were positively proportional to serum T4 binding. They concluded that:
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