Methods of diagnosing small intestinal bacterial overgrowth (SIBO) and SIBO-related conditions

A method for detecting small intestinal bacterial overgrowth (SIBO) in a human subject by corroborating the relative amounts of methane, hydrogen, and at least one sulfur-containing gas with the presence or absence of SIBO, said method comprising:

• administering a controlled quantity of an isotope-labeled sugar, a sugar that is poorly digestible by a human or an isotope-labeled sugar that is poorly digestible by a human, to produce a gas mixture, said gas mixture being at least partially produced by the intestinal microflora of said human subject;
• and
• detecting the relative amounts of methane, hydrogen, and at least one sulfur-containing gas in said gas mixture exhaled by said human subject, wherein
• i) an amount of methane, hydrogen, or at least one sulfur-containing gas that is above a normal range for a healthy human subject for the methane, hydrogen, and/or at least one sulfur-containing gas is corroborated with the presence of SIBO;
• ii) an amount of methane and/or hydrogen that is less than an amount of the at least one sulfur-containing gas is corroborated with the presence of SIBO;
• iii) an amount of methane, hydrogen, and at least one sulfur-containing gas that is below the normal range for a healthy human subject for methane, hydrogen, and at least one sulfur-containing gas is corroborated with the absence of SIBO;
• or
• iv) an absence of methane, hydrogen, or at least one sulfur-containing gas is corroborated with the absence of SIBO.