Validation of a simple diet self-assessment tool (SDSAT) in head and neck cancer patients undergoing radiotherapy

Purpose: The simple diet self-assessment tool (SDSAT) is a simple instrument for estimating the cancer patients' dietary intake. This study aimed to evaluate its reliability and validity among head and neck (HNC) cancer patients undergoing radiotherapy (RT).

Methods: Two studies were conducted at the department of radiation oncology of a University-affiliated hospital, where HNC patients were assessed at baseline, mid-treatment and post-treatment of RT. In the first study, 25 patients (a total of 60 cases) were recruited by convenience sample method to estimate the interrater reliability of SDSAT. Then, 304 patients (a total of 912 cases) were involved in a prospective, longitudinal observational study. The criterion validity was confirmed by the agreement rate between SDSAT and 24-h dietary recall (24HR). The predictive validity was established by exploring the impact of the score of SDSAT on weight loss among HNC patients during RT.

Results: The estimation of interrater reliability of SDSAT showed that weighted kappa was 0.82 (95%CI = 0.74-0.90, p < 0.001), suggesting a high level of agreement between two raters. The overall agreement rate between SDSAT and 24HR was 62.9% (574/912) and weighted kappa was 0.66 (95%CI = 0.63-0.70, p < 0.001), which indicated good criterion validity. Generalized estimating equation (GEE) showed that the score of SDSAT had a significant impact on weight loss (β = 1.40, 95%CI = 1.21-1.59, p < 0.001), which demonstrated good predictive validity.

Conclusions: The SDSAT demonstrated favorable reliability and validity. It is appropriate for estimation of dietary intake among HNC patients.