內化烙印量表應用於精神疾患病人之再測能力和最小可偵測之變化值

Reproducibility and Minimal Detectable Change of Internalized Stigma of Mental Illness (ISMI) Scale in Patients with Mental Illness

目的：內化烙印 (self-stigma) 是值得注意的重大議題，而內化烙印量表 (Internalized Stigma of Mental Illness; ISMI) 是常用來測量內化烙印的工具之一。然而，ISMI 的再測能力，尤 其是最小可偵測之變化值仍未建立。因此，臨床應用 ISMI 仍有其限制。本研究目的為瞭解 ISMI 於不同長度的再測時，應用於精神疾患病人上的再測能力表現。方法：精神疾患病人 (n = 145) 填寫兩次 ISMI，間隔時間為 2 周至 3 個月；116 人間隔 2 個月內；75 人一個月內。 用組內相關係數 (intraclass correlation coefficient, ICC) 瞭解再測能力並計算最小可偵測之變化 值。再使用最小可偵測之變化值百分比瞭解再測能力是否符合預期（ < 30% 表示可接受）。 結果：ISMI 的再測能力隨再測間隔愈短愈好（ 3 個月間隔：ICC = 0.53-0.80；2 個月間隔： 0.55-0.82；1 個月間隔：0.69-0.89）。ISMI 總分的最小可偵測之變化值為 19.57（ 3 個月間 隔）、19.26（ 2 個月間隔）、14.08（ 1 個月間隔）。最小可偵測之變化值百分比顯示 ISMI 總分在三個月間隔的再測能力接近可接受 (30.16%, p < 0.05)，而二個月和一個月的間隔為可 接受（ 29.44% 和 21.74%, p < 0.05）。結論：ISMI 總分應用於精神疾病患者時，在兩個月內 的間隔具有良好的再測能力。

Objective: Self-stigma which is a critical issue, needs to be cared by the mental health professionals, and the Internalized Stigma of Mental Illness (ISMI) scale is one of the most commonly used instrument measuring self-stigma. But the information of its reproducibility, especially the minimal detectable change (MDC), remains largely unknown. Therefore, the applicability of the ISMI is somewhat limited. In this study, we intended to study the reproducibility of the ISMI in patients with mental illnesses through different lengths of test-retests. Methods: People with mental illness (n = 145) completed the ISMI twice within an interval of 2 weeks to 3 months; 116 of them within 2 months; and 75 within 1 month. The intraclass correlation coefficient (ICC) was used to examine the reproducibility, and MDC was further calculated using ICC results. Furthermore, MDC% was computed to understand whether the reproducibility is acceptable (< 30% indicates acceptable). Results: The reproducibility of the ISMI was better in a shorter testretest interval (3-month interval: ICC = 0.53 to 0.80; 2-month: ICC = 0.55 to 0.82; 1-month: ICC = 0.69 to 0.89). The MDC for the total score of the ISMI was 19.57 (three-month interval), 19.26 (two-month interval), and 14.08 (one-month interval). We also found that the patients had significantly reduced self-stigma in one month (p < 0.05). MDC% revealed that the reproducibility for the total score of the ISMI was nearly acceptable in three-month interval (30.16%) and acceptable in 2- and 1-month intervals (29.44% and 21.74%, p < 0.05). Conclusion: The total score of the ISMI is reliable in monitoring the self-stigma in patients with mental illness within an interval of two months.