Factors affecting blood alcohol concentration (BAC) estimation and drinking intention during voluntary breath testing (VBT) : a cross-sectional study

This study aimed to assess the accuracy and factors influencing blood alcohol concentration self-estimation during voluntary breath testing. It also aimed to assess whether intended drinking behaviour changed after reviewing blood alcohol concentration and factors influencing this. A total of 462 Australian music festival patrons aged 18–40 years completed a survey exploring factors likely to affect estimation accuracy and provided an estimation of their blood alcohol concentration. A breathalyser reading was taken and participants were asked whether reviewing this reading changed their drinking intentions. Most respondents (58.4%) were accurate within 0.02% range, while 11.4% underestimated and 29.1% overestimated. Machine-read blood alcohol concentration was the most significant estimation accuracy predictor. Reviewing their readings changed the intention to drink in one-third of participants, indicating that voluntary breath testing may influence future drinking behaviour. Underestimation was associated with intention to drink less, whilst completing the survey earlier and <1 h since last drink was associated with intention to drink more.