The Thyroid Cancer Modified Anxiety Scale (TC-MAX): Development and External Validation of a Thyroid Cancer Distress Instrument.

BACKGROUND

Patient distress associated with thyroid cancer greatly influences treatment choice, yet is underestimated by clinicians. We developed and validated the Thyroid Cancer Modified Anxiety Scale (TC-MAX) to measure patient-reported thyroid cancer-related worry.

METHODS

Development entailed (1) conceptualization (systematic literature review, expert panel [n = 4], patient focus groups [n = 10]); (2) qualitative revision (pilot testing [n = 59], expert panel [n = 4], patient feedback [n = 4]); (3) internal validation (n = 148); and (4) external validation (n = 1002), with papillary thyroid cancer patients. Internal consistency, test-retest reliability, exploratory/confirmatory factor analysis, and construct validity were evaluated. Severity categories and minimal clinically important differences (MCIDs) were determined.

RESULTS

An 18-question scale was constructed, encompassing three subscales (Collective Anxiety, Ultrasound Anxiety, and Fear of Recurrence/Progression). Internal validation revealed high internal consistency (Cronbach's α = 0.93), excellent test-retest reliability (intraclass correlation coefficient [ICC] 0.86), and significant construct validity (Distress Thermometer [Spearman's ρ = 0.56, p < 0.001], Hospital Anxiety Depression Scale [HADS] [Spearman's ρ = 0.52, p < 0.001], and Functional Assessment of Cancer Therapy-General [FACT-G] [Spearman's ρ = -0.50, p < 0.001]). Exploratory factor analysis showed expected loadings for respective subscales, and confirmatory factor analysis confirmed that the structure was parsimonious. External validation exhibited similar psychometrics, including internal consistency (Cronbach's α = 0.94), test-retest reliability (ICC 0.87), and construct validity (Distress Thermometer [Spearman's ρ = 0.54, p < 0.001], HADS [Spearman's ρ = 0.67, p < 0.001], and FACT-G [Spearman's ρ = -0.62, p < 0.001]). Proposed ranges (low = 0-26, moderate = 26-43, and severe = 43-100) were in excellent agreement between internal and external validation cohorts (weighted κ = 0.84, p < 0.001). Anchor-based MCID was found to be 16.7 (active surveillance vs. surgery) (25.9 [standard deviation (SD) ± 16.4] vs. 42.6 [SD ± 23.3], p < 0.001) or 16.9 (hemithyroidectomy vs. thyroidectomy) (33.6 [SD ± 17.4] vs. 50.5 [SD ± 24.1], p = 0.005).

CONCLUSIONS

TC-MAX represents the first dedicated measure of anxiety in thyroid cancer. It exhibits robust psychometric properties in a vulnerable population, accounting for complex viewpoints. The scale effectively assesses preference and informs patients, including determining fit for active surveillance or extent of surgery.