Breath ammonia level is ‘a reliable tool’ to screen for early stages of CKD
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As breath ammonia concentration increased at each chronic kidney disease stage and correlated with eGFR and CKD biomarkers, researchers said it can be used to screen for “non-life threatening or non-serious CKD” at a cutoff of 886 ppb.
“Finding a tool to predict kidney function without visiting hospitals is an attractive method for CKD monitoring in [the] COVID-19 pandemic,” Ya-chung Tian, MD, of the Linkou Chang Gung Kidney Research Center and department of nephrology in Taoyan, Taiwan, wrote in an abstract presented at ASN Kidney Week. “The present study aimed to investigate whether exhaled breath ammonia measurement could be used for rapid CKD screening.”
Tian enrolled 121 patients with CKD stages 1 to 5 (average age, 61 years; 62 patients were men) and compared breath ammonia level measurements with blood urea nitrogen (BUN), creatine and eGFR levels. Tian wrote there were no significant differences between patients in each stage regarding sex, body weight, hemoglobin, albumin, comorbidities and medication and that BUN level, creatinine and eGFR increased with each CKD stage.
Breath ammonia level correlated with BUN, serum creatinine, eGFR and inversed eGFR levels. Breath ammonia concentration was increasingly elevated at each stage of CKD (stage 1: 636 ± 94 ppb; stage 2: 1,020 ± 326 ppb; stage 3: 1,943 ± 326 ppb; stage 4: 4,421 ± 1,042 ppb; stage 5: 12,781 ± 1,807 ppb). The area under curve for a breath ammonia level cutoff concentration of 1,187 ppb comparing patients with eGFR of at least 60 mL/min/1.73 m2 with patients with eGFR of no more than 60 mL/min/1.73 m2 was 0.831 (positive predictive value, 0.84; negative predictive value, 0.61; sensitivity, 71%; specificity, 78%). Tian wrote “at 886 ppb, the sensitivity increased to 80% but the specificity decreased to 69%.”
“Because CKD is non-life threating and breath ammonia detection was conducted in real time, inexpensive, easy to administer and had an acceptable diagnostic accuracy, breath ammonia can be used as a good surrogate for kidney function and a reliable tool for CKD screening,” Tian wrote.
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Tian Y. Breath ammonia is a useful biomarker predicting kidney function in CKD patients. Presented at: ASN Kidney Week. Oct. 22-25 (virtual meeting).
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