Reliability of individual thyroid function tests in the assessment of thyroid dysfunction

ABSTRACT

We studied commonly used thyroid function tests [T4, T3, TSH, FT4I, FT3I, by RIA] as regards their diagnostic value, namely sensitivity, specificity, efficiency and predictive value in the evaluation of various types of thyroid dysfunction. Subjects were subdivided into a control group [n=22] and 4 clinical groups based on preliminary clinical evaluation which used standard data work sheets both for hyper and hypothyroidism in the Egyptian group of study. The groups included a hyperthyroid [n=38], hypothyroid [n=33], euthyroid [n=18] and hypothyroid group on thyroxin replacement therapy [n=31] including both Egyptian and American patients. The predictive value model was applied for the evaluation of thyroid function tests. Sensitivity and efficiency of the studied thyroid parameters were found higher among the Egyptian group than the USA group emphasizing the importance of careful clinical assessment prior to ordering laboratory tests. The most appropriate one step and two step tests were [T3 and T4 + T3] for hyperthyroidism, TSH and TSH + T4 for hypothyroidism, T4 and TSH + T3 for euthyroidism and T4 and T4 + TSH to monitor hypothyroid patients under thyroxin placement therapy. Careful clinical assessment and proper laboratory ordering according to the previous findings, may save much time and cost and may add to the accuracy of laboratory diagnosis of thyroid function