SUN-241 - Semi-Quantitative Reference Card Method for Point-of-Care Cortisol Assessment in Adrenal Venous Sampling

Background

Adrenal venous sampling (AVS) is the gold standard for subtype classification in primary aldosteronism (PA); however, the success rate depends on operator expertise. A previously developed rapid cortisol measurement kit based on competitive immunochromatography shows test line color intensity inversely correlated with cortisol concentration (stronger red indicates lower cortisol). While quantitative evaluation using a dedicated immunoreader can improve AVS success by enabling immediate resampling of inappropriate samples, the requirement for dedicated equipment poses challenges in introduction cost and usage environment constraints.

Objective

To establish a semi-quantitative measurement method using a reference card that eliminates the need for quantitative equipment while maintaining the rapidity of the rapid cortisol kit, and to validate its methodological validity and clinical utility in determining AVS success.

Methods

We retrospectively analyzed 236 samples from 48 PA patients at two institutions using data from a multicenter study (November 2019–March 2021). In the conventional method, cortisol and aldosterone were measured by laboratory testing. In the semi-quantitative method, test strip bands were photographed under standardized conditions. A reference card displaying stepwise standardized color intensities for predetermined cortisol concentration ranges was created. Each sample's color was visually compared to select the most similar tone for semi-quantitative conversion. AVS success was determined using these values, and sensitivity, specificity, and correlation with conventional method were evaluated.

Results

The semi-quantitative method demonstrated high diagnostic performance with sensitivity of 0.94 and specificity of 0.91. Cortisol values showed good agreement and significant correlation with the conventional method, confirming sufficient analytical validity despite visual evaluation.

Conclusion

The semi-quantitative rapid cortisol measurement using a reference card enables real-time evaluation of sample adequacy during AVS. This equipment-free, portable method is suitable as Point-of-Care Testing (POCT), allowing immediate catheter repositioning and resampling decisions. It offers advantages in reduced introduction costs and environmental flexibility. This simple method contributes to improving AVS success rates while reducing retesting risks and clinical burden.

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