Breath ammonia test for chronic kidney disease screening: impact of fasting on diagnostic accuracy

ABSTRACT Background Chronic kidney disease (CKD) is a global health concern and early detection is crucial for preventing progression. Current screening methods are inconvenient and resource intensive. Breath ammonia has been proposed as a non-invasive biomarker for renal dysfunction but its diagnostic accuracy and the impact of fasting remain unclear. This study aimed to validate the breath ammonia test for CKD screening and assess the effect of fasting on its diagnostic performance. Methods This prospective study included 244 participants: a derivation cohort (n = 121) and a validation cohort (n = 123). Breath ammonia was measured using a vertical-channel organic semiconductor sensor. Estimated glomerular filtration rate (eGFR) was calculated using the Modification of Diet in Renal Disease equation. Receiver operating characteristics (ROC) curve analysis was used to evaluate diagnostic performance, and fasting was defined as ≥4 hours without intake. Results The average age of the participants was 60.7 years, with males comprising 51% of the cohort. Breath ammonia levels significantly correlated with serum creatinine (r = 0.695, P < .001), eGFR (r = −0.533, P < .001) and blood urea nitrogen (r = 0.765, P < .001). Using a cut-off of 886 ppb, breath ammonia predicted eGFR