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 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. eGFR was calculated using the MDRD equation. 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 0.001), eGFR (r = -0.533, P 0.001), and BUN (r = 0.765, P 0.001). Using a cutoff of 886 ppb, breath ammonia predicted eGFR 60 mL/min/1.73 m² with a sensitivity of 78.5% and a specificity of 81.6% (AUROC = 0.842). Fasting enhanced diagnostic accuracy, improving sensitivity and specificity to 87.9% and 91.5%, respectively (AUROC = 0.939). Conversely, non-fasting patients demonstrated lower sensitivity at 74.5% and specificity at 74.6% Conclusions Breath ammonia test is a promising non-invasive CKD screening tool. Standardizing pre-test fasting may further improve its diagnostic accuracy.