Novel methods to determine 
matrix metalloproteinase (MMP) activity are described. In a typical embodiment of the invention, the 
biological fluid sample is from a patient, and the methods of the invention are useful to assess 
disease severity or progression, diagnose a particular 
disease, or develop a profile of MMP activity for inflammatory diseases such as 
arthritis, or 
cancer. A novel method of the invention involves the use of particular 
amino acid sequences in substrates that include but are not limited to 
fluorescence, colorimetric, radiometric and unlabeled substrates. A second method of the invention use neo-
epitope antibodies that bind to the cleavage sites generated by 
collagenase 3 
digestion of 
type IV collagen or biglycan or the 
peptide substrates disclosed. There is also provided a diagnostic kit for use in determining the amounts of MMP activities in biological samples comprising (a) one or more substrates with different specificities against the MMPs, (b) one or more reagents capable of inhibiting non-
metalloproteinase activities, (c) one or more reagents capable of specifically inhibiting 
metalloproteinase activities, (d) one or more activators of 
metalloproteinase activities, (e) reagents capable of altering the selectivity ratios for the substrates such as 
gelatin or 
type II collagen, and (f) 
collagenase 3, stromelysin 1, 
gelatinase A, 
gelatinase B and / or 
collagenase 1 as calibration standards.