Abstract 9

Objective: To determine the usefulness of measuring basal TSH levels with sensitive methods (bTSHs) in comparison to TSH response to TRH test in pediatric patients. Subjects and methods: We studied retrospectively the results of 332 TRH/TSH tests performed in children (2 to 18.5 years old) suspected to have primary thyroid disorders. One hundred and sixty five tests were analyzed using an immunofluoromethric method (IFMA) and 167 an immunorradiometric assay (IRMA). Basal TSH levels, absolute increment (max TSH) and relative increment (Δ TSH: maxTSH - Basal TSH) were evaluated Statistical analysis was performed with logarithmically transformed data. Responses to TRH test were classified according to the 5th and 95th percentiles of max TSH and Δ TSH values of 67 normal children studied with IRMA in: insufficient, normal and hyperresponsive. IRMA/IFMA; bTSH s / maxTSH, bTSHs/ Δ TSH correlations were calculated. Sensitivity (S) and specificity (E) of bTSHs was calculated in relation ship with max TSH and Δ TSH with both methods. Results of IFMA TRH/TSH were evaluated at different intervals of bTSHs. Results: IFMA/IRMA correlation was statistically significant (r: 0.99, p < 0.01). A significant correlation was found in bTSHs/max TSH (r: 0.80; p < 0.001) and in bTSHs/ΔTSH (r: 0.68; p < 0.01). S of bTSHs in relation to max TSH was 68% and E 96% S and E in relation to Δ TSH were 60% and 96.5% respectively. Results of FMA TRH/TSH tests showed: Table Conclusion: Basal TSHs correlates with maxTSH and ΔTSH of TRH/TSH test with good S and excellent E. Only 2.7% of patients with bTSHs < 3 uU-ml had an exaggerated response to TRH and 1 out of 3 patients were hyperresponsive with bTSHs between 3 and 5 uU-ml. TRHtest in diagnosis of hypothyroidism should be considered in those patients with bTSHs between 3 and 5 uU/ml.

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