Anxiety is one of the most common problems among nursing students. The State-Trait Anxiety Inventory (STAI) is used to detect anxiety in this population; however, its length hinders speedy detection. For this reason, a faster and more efficient instrument is needed for early detection. This study aimed to determine the relationship between the anxiety measurement scales State-Trait Anxiety Inventory (STAI) and the Visual Analogue Scale for Anxiety (VAS-A) by establishing a discrimination threshold through the contrast of true positive rates (VPR) and false positive rates (FPR). To this end, a cross-sectional quantitative observational and analytical study was carried out on 185 fourth-year nursing students. The data collected were anxiety (STAI and VAS-A) and socio-demographic variables during the COVID-19 pandemic. The results showed a correlation between the two scales (VAS-A and STAI). The VAS-A is a useful instrument for assessing students in a crisis that could potentially generate anxiety. The study established a reasonably safe error probability range (>5%), allowing the VAS-A scale to be used as a rapid diagnostic or pre-diagnostic tool, depending on the scores. The study shows that speedy detection of anxiety using the VAS-A and an in-depth approach with the STAI by teaching staff in crises is possible.