The additive clinical value of combined thyroglobulin and antithyroglobulin antibody measurements to define persistent and recurrent disease in patients with differentiated thyroid cancer

Abstract

To evaluate retrospectively the additive clinical value of combined thyroglobulin (Tg) and antithyroglobulin antibody (TgAb) measurements to define recurrent and persistent disease in patients with differentiated thyroid cancer. 181 patients with differentiated thyroid cancer were included in the study. The nonstable disease group (recurrent and persistent disease) had 61 patients with 24-36 months follow-up period. The stable disease group (without recurrence or persistence) had 120 patients with 21-28 months follow-up period. We compared Tg and combined Tg-TgAb levels on the sixth month after the ablation between two groups. Optimal threshold values for Tg, TgAb measurements were calculated statistically as 4.45 ng/ml and 27.8 IU/ml. Optimal sensitivity and specificity for 4.45 ng/ml Tg levels were 52.5 and 91.7%. We also evaluated different Tg threshold values. We found sensitivity was 54.2% and specificity 86.7% for 2 ng/ml and sensitivity was 40.7% and specificity 96.7% for 10 ng/ml Tg levels. By the odds ratio (OR) rule, the obtained sensitivity and specificity were 68.3 and 90% (if Tg>10 ng/ml or TgAb>27.8 IU/ml), 78.3 and 90% (if Tg>4.45 ng/ml or TgAb>27.8 IU/ml), and 80% and 85% (if Tg>2 ng/ml or TgAb>27.8 IU/ml). Sensitivity increased with statistical significance from 52.5 to 78.3% (P<0.001) and decreased with statistical insignificance from 91.7 to 90% (P>0.05) for the optimal thresholds. Combined Tg-TgAb values were found more useful than only Tg for recurrent and persistent diseases. Combined Tg and TgAb measurements seemed to be a useful marker.