A method of determining in an individual the presence, identity, and/or severity of a disease or condition associated with abnormal glycan biosynthesis, degradation, or accumulation, the method comprising: (a) generating a first biomarker comprising a glycan residual compound, wherein the first biomarker is generated by treating a population of glycans, in or isolated from a biological sample from the individual suspected of suffering from a disease or condition associated with abnormal glycan accumulation, biosynthesis, and/or degradation, with at least one digesting glycan enzyme, wherein the first biomarker is a non-reducing end glycan residual compound; (b) generating a second biomarker comprising a glycan residual compound, wherein the second biomarker is generated by treating a population of glycans, in or isolated from a biological sample from the individual suspected of suffering from a disease or condition associated with abnormal glycan accumulation, biosynthesis, and/or degradation, with at least one digesting glycan enzyme in the same or different digestion step as provided in step (a), wherein 1) the second biomarker is a reducing end glycan residual compound; 2) the second biomarker is an internal glycan residual compound, or 3) when the individual is suspected of suffering from a disease or condition associated with abnormal glycan accumulation, biosynthesis, and/or degradation, the second biomarker is a biomarker generated by treating the first non-reducing end glycan residual compound biomarker with the glycan degradation enzyme that is functioning abnormally in said disease or condition from which the individual is suspected to suffer; (c) using an analytical instrument to detect the presence of and/or measure the amount of the first and second biomarker produced and displaying or recording the presence of or a measure of a population of the first and second biomarkers, and (d) monitoring and/or comparing the amounts of the first and second biomarkers in the biological sample, determining a ratio of the first biomarker to the second biomarker in the individual suspected of suffering from a disease or condition associated with abnormal glycan accumulation, biosynthesis, and/or degradation; wherein the ratio of the first biomarker to the second biomarker is utilized to determine the presence, identity, and/or severity of the disease or condition, wherein prior to the enzyme treatment, the first and second biomarkers are not present in abundance in samples from a population of individuals with the disease or condition relative to a population of individuals without the disease or condition. (a) generating a first biomarker comprising a glycan residual compound, wherein the first biomarker is generated by treating a population of glycans, in or isolated from a biological sample from the individual suspected of suffering from a disease or condition associated with abnormal glycan accumulation, biosynthesis, and/or degradation, with at least one digesting glycan enzyme, wherein the first biomarker is a non-reducing end glycan residual compound; (b) generating a second biomarker comprising a glycan residual compound, wherein the second biomarker is generated by treating a population of glycans, in or isolated from a biological sample from the individual suspected of suffering from a disease or condition associated with abnormal glycan accumulation, biosynthesis, and/or degradation, with at least one digesting glycan enzyme in the same or different digestion step as provided in step (a), wherein 1) the second biomarker is a reducing end glycan residual compound; 2) the second biomarker is an internal glycan residual compound, or 3) when the individual is suspected of suffering from a disease or condition associated with abnormal glycan accumulation, biosynthesis, and/or degradation, the second biomarker is a biomarker generated by treating the first non-reducing end glycan residual compound biomarker with the glycan degradation enzyme that is functioning abnormally in said disease or condition from which the individual is suspected to suffer; 1) the second biomarker is a reducing end glycan residual compound; 2) the second biomarker is an internal glycan residual compound, or 3) when the individual is suspected of suffering from a disease or condition associated with abnormal glycan accumulation, biosynthesis, and/or degradation, the second biomarker is a biomarker generated by treating the first non-reducing end glycan residual compound biomarker with the glycan degradation enzyme that is functioning abnormally in said disease or condition from which the individual is suspected to suffer; (c) using an analytical instrument to detect the presence of and/or measure the amount of the first and second biomarker produced and displaying or recording the presence of or a measure of a population of the first and second biomarkers, and (d) monitoring and/or comparing the amounts of the first and second biomarkers in the biological sample, determining a ratio of the first biomarker to the second biomarker in the individual suspected of suffering from a disease or condition associated with abnormal glycan accumulation, biosynthesis, and/or degradation;