背景:治療後之分化良好型甲狀腺癌(well-differentiated thyroid carcinoma; WDTC)通常以碘-131全身掃描( 1311 whole body scan;山I WBS)及血清甲狀腺球蛋白(serum thyrogobu1in; Tg)來追蹤其復發或轉移。本研究針對本院 WDTC病忠所實施的Tg測定及山I WBS結采作回溯性分析 及比較，期能評估此兩種方法對WDTC病患復發或轉移病性的偵測價值及建立預測WDTC復發或轉移之Tg正常臨界值(cut-off value) 0

方法:112例曾接受過甲狀腺全切除或近甲狀腺全切除術 及至少100mCi之碘-131成功地將腫為殘餘組織摘除的 WDTC病患，分別施以系列131I WBS檢查及血清Tg測定; 再分析凹IWBS對其中的例兵役發或轉移者之偵測靈敏度 與專一度，並採用Tg= 1，2，4，8μgIL作為臨界值，分別計 算於1星發或轉移性病娃偵測之靈敏度與專一度，選擇適當的Tg值，作為正常臨界值。

結果:18例具復發或轉移的患者中，有13例其山I WBS呈 況陽性，偵測靈敏度為729毛(13/18);如例未見復發或轉移之病患中，有88例主現陰性，偵測專一度為949毛(88/94) 0 18例具復發或轉移的患者血清Tg平均值為171.8 ± 110.7μgIL '94例未見復發或轉移之病患血清Tg平均 值為1.8± 0.5μg且，兩相比較具統計學上之顯著差異;採 用不同的Tg作為正常臨界值，有不同的陽性檢測l率;以Tg三三IμgIL作為臨界值，偵測靈敏度為949毛(17/18) ，專一度為789毛(73月4)，以2μgiL作為臨界值，靈敏度為899毛(16/18) ，專一度亦為899毛(84/94)，以4μgIL為臨界值，靈敏度為729毛(13/18)，專一度為969毛(90194)，以8μgiL為臨界佳，靈敏度為679毛(12/18) ，專一度為989毛(92/94)。若以山I WBS結合Tg 至2μgiL作為正常臨界值，則偵測之靈敏度約可達949毛(17/18)，專一度亦達919毛(86/94)。

結論:131IWBS對WDTC復發或轉移病仕的偵測具高專一性、低靈敏度，而Tg封WDTC復發或轉移病性的偵測具高靈敏度，兩者具互補作用，若配合Tg三三2μgIL作為正常臨界佳，則可以有效地提高偵浪'JWDTC復發或轉移病仕的靈敏度及專一性。當然，對Tg分界值的設定則須參考病人預後危險因子。

Background: 1311 whole body scan (WBS) and serum thyrogobulin (Tg) measurement are routinely used to follow up the recurrence or metastasis of well-differentiated thyroid carcinoma (WDTC). This study retrospectively analyzed WDTC patients by using the results of WBS and Tg to determine the optimal cut-off value to predict the recurrence or metastasis of WDTC.

Methods: WBS and serum Tg measurements were examined in 112 WDTC patients who received total or near total thyroidectomy and at least 100 mCi of 1311 thyroid ablation therapy. Of them， 18 patients were diagnosed with recurrences or metastases. Sensitivity and specificity for presence of disease using WBS were calculated. In addition， sensitivity and specificity of serum Tg using four cut-off values (Tg= 1，2，4， or 8μgiL) were measured. The most optimal cut-off value of Tg by both WBS and Tg to predict the recurrence or metastasis of WDTC was determined.

Results: For the recurrent group， 12 of 18 had positive finding in WBS; For the non-recurrent group， 88 of 94 negative finding in WBS. The sensitivity， specificity of the WBS for detecting recurrences and metastases were 72% (12/18) and 94% (88/94) retrospectively. For the recurrent group， 171.8 ± 110.7μgiL of serum Tg was measured， and 1.8 ± 0.5 J1giL of serum Tg was measured in the non-recurrent group. Variable detective rates were found when the cut-off values Tg were selected differently. The sensitivity， specificity of serum Tg for detecting disease recurrence were 94% and 78% when the cut-off value was set at 1μgiL; 89% vs. 89% at 2μgiL; 72% vs. 96% at 4μgiL and 67% vs. 98% at 8 J1giL.

Conclusions: 1311 WBS has a high sensitivity， but a low specificity for the detection of recurrent or metastatic WDTC. Both WBS and Tg measurement are complementary for the detection of disease. Our results suggest that using WBS and 2μgiL cut-off value of Tg could be optimal for the detection of recurrent or metastatic WDTC. However， patients' prognostic risk factor should be taken in account in this regard.