Disclosed is a method for measuring a level of pyridinoline and/or deoxypyridinoline in a sample. In the method, a non-hydrolyzed sample containing one or more peptide-bound collagen pyridinium crosslinks selected from the group consisting of pyridinoline, deoxypyridinoline, or both, is contacted with a protease reagent under conditions effective for the protease reagent to cleave the crosslinks from attached collagen amino acids and peptides, so that peptide-bound forms are converted to native, peptide-free pyridinoline and deoxypyridinoline. After proteolysis, the level(s) of native, peptide-free pyridinoline and/or deoxypyridinoline are measured. Preferably, proteolysis is effective to ensure that at least 80% of total pyridinium crosslinks are present as the native, peptide-free forms. The method is particularly useful in screening or monitoring collagen degradation activity. Kits and reagents for use in the method are also disclosed.

Disclosed is an improvement in the analysis for an analyte in a urine test sample in which the urine is contacted with a labeled antibody specific to the analyte and the concentration of the analyte is determined by measuring the response from the label. The improvement involves maintaining the concentration of urea in the test sample above the threshold value which value is the concentration of urea at which increases in the urea concentration do not affect the accuracy of the assay such as by interfering with the binding between the analyte and the labeled antibody.