Objective: The use of the Distress Thermometer (DT) to identify those who are distressed and require further psychological evaluation is well established for cancer patients. However, partners of patients also experience distress yet the validity of this brief screening tool in partners of patients with cancer, and specifically prostate cancer (PCa), is relatively unknown.

Methods: Receiver operating characteristics analyses were used to assess the accuracy of the DT compared to validated measures of general (Hospital Anxiety and Depression Scale [HADS]) and cancer‐specific (Impact of Events Scale– Revised [IES‐R]) distress in two prospective surveys of partners of men with PCa (n = 189, Study 1 and n = 460, Study 2). In Study 1, participants were partners of men with localised PCa (recruited around diagnosis) about to undergo or had received surgical treatment, and in Study 2 participants were partners of men diagnosed with PCa who were 2–4 years post‐treatment.

Results: In Study 1: the diagnostic accuracy of the DT compared to the HADS was acceptable (area under the curve (AUC) range 0.71‐0.84) yet the confidence intervals associated with the AUCs were wide. Optimal DT thresholds varied from ≥2 to ≥5 and sensitivity, a key performance indicator in this context, was low (range 50.00‐87.50). In Study 2: for the HADS the AUCs indicated good discriminatory ability of the DT (range 0.80‐0.92). However, there was variability in the DT thresholds (range ≥1 to ≥4) and while sensitivity values were high specificity values were lower than required. Against the IES‐R, AUCs were high (range 0.83‐0.94) and DT thresholds ranged ≥3 to ≥5. Sensitivity and specificity were more evenly balanced when the DT was compared to the IES‐R.

Conclusions: No clear patterns were identified with respect to the performance of the DT across comparator constructs or over time. As a result, it is not possible to recommend the ideal cut‐off for use of the DT to detect partners of men with PCa who are distressed. Future research is therefore required to identify an optimal screening tool for partner distress.