13C-α-Ketoisocaproic Acid Breath Test Revisited: An In-Depth Reproducibility Study Advocates an Extended Breath Sampling Period

Abstract

In this study we sought for a quantitative parameter which would offer the best reproducibility of a standard (13)C-alpha-ketoisocaproic acid ((13)C-KICA) breath test. On 3 separate days 14 healthy volunteers (7 females, 7 males) took orally 1 mg/kg body mass (13)C-KICA and 20 mg/kg body mass L-leucine. Samples of expiratory air for (13)CO(2) measurement with the use of isotope ratio mass spectrometry were collected every 5 min during the first hour and then at 70, 80, 90, 105, 120, 150, 180, 240, 300, 360, 540, 720, and 1440 min. Short-term reproducibility assessment involved paired examinations taken 3.5 days apart; paired examinations separated by 22 days (median) served for the medium-term reproducibility assessment. T(max), the time to reach the maximum momentary (13)C recovery (D(max)), showed an unsatisfactory reproducibility, and the D(max) displayed a fairly good reproducibility, whereas the cumulative (13)C recovery calculated for a time span within the range 0-90 and 0-120 min exhibited the best reproducibility. In no case did the medium-term reproducibility prove any worse than the short-term one. Taking into account its reproducibility, the cumulative (13)C recovery appears to be the most reliable parameter of the (13)C-KICA breath test.

Energy restriction in obese subjects impact differently two mitochondrial function markers

“…The KICA-BT is based on the activity of the branched-chain ketoacid dehydrogenase complex (11). This enzyme resem- bles closely related with the citrate cycle (1).…”

“…The 13 C-enrichment in breath was measured by isotope ratio mass spectrometry and the cumulative tracer recovery calculated for a time span within the range 0-120 min (AUC; %13C) and the maximal oxidative rate (Dmax; %13C/h) were calculated as described elsewhere (11,25).…”

Exact profiles of 13CO2 recovery in breath air after per oral administration of [13C]methacetin in two groups of different ages

“…The determined 13 CO 2 content within the total pool of the exhaled CO 2 was expressed in δ‰ PDB units, i.e. relative to the international standard -the calcium carbonate of the fossil Belemnitella of the cretaceous Pee Dee formation in South Carolina, USA (zero δ‰ PDB corresponds to 1.11123% 13 C atoms within CaCO 3 ) [23]. The net changes in the 13 CO 2 concentration were conveyed as DOB (delta over baseline) units (in ‰) according to the formula:…”

13C-methacetin breath test reproducibility study reveals persistent CYP1A2 stimulation on repeat examinations

“…Breath tests performed with the use of stable isotopes, such as 13 C, cannot be considered an exception in this respect, especially because during the past decade their clinical use has been constantly growing [24,34,35] . An increase in the number of relevant scientific papers indicates that, from among the tests dedicated to assess the activity of cytochrome P450, known as the microsomal breath tests, the 13 C-MBT has lately taken the lead.…”

“…Following the procedures described previously [20,23,24] , curves of the momentary and cumulative recovery of 13 C in the exhaled air relative to the administered oral dose of 13 C-methacetin were constructed within the time domain of 0 to 180 min. Subsequently the following parameters were derived: Dmax -the maximum momentary 13 C recovery in expiratory air, Tmax -the time elapsing from the intake of the substrate until the occurrence of the Dmax, and AUCi -the cumulative 13 C recovery within …”