Predictive validity of the original and expanded susceptibility scales for smokeless tobacco

This study seeks to validate the original and expanded susceptibility scales for smokeless tobacco (SLT) use among a longitudinal sample of rural male youth. We also compare the predictive validity of both scales for SLT.

Data are from a five-wave longitudinal sample of rural males in the Unites States aged 11-16 at baseline. Data were collected from January 2016 to December 2018. We used a series of logistic regressions to identify whether individual demographic variables, the original (use SLT soon, in next year, if friend offers), or the expanded (original plus curiosity) susceptibility scales predicted experimentation with SLT by 2018. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of both scales were also calculated to determine reliability. All analyses were limited to 2016 never SLT users.

Both susceptibility scales were significant predictors of SLT initiation by follow-up. Susceptible youth had three times the odds of SLT initiation by follow-up compared to youth who were non-susceptible. Both scales have high specificity, identifying a large proportion of never users as non-susceptible. Sensitivity for the original scale was 37.0% and increased to 44.2% for the expanded scale. The PPV was approximately 20% for both the original and expanded scales.

The SLT susceptibility scales are valid for predicting future SLT initiation; however, there remains room for improvement as the sensitivity of both scales is relatively low compared to the smoking scale. Future research should examine additional methods to identify youth at risk of SLT initiation.