Characteristics of the ideal biomarker and of PYD in rheumatoid arthritis.
| Biomarker | Ideal (i.e., HbA1c) | PYD |
|---|---|---|
| Objectively measured | + | + |
| Indicator of normal biology | + | + |
| Indicator of the pathologic process | + | + |
| Indicator of response to therapy | + | ? |
| Indicator of prognosis | + | + |
| Indicator of modification of the pathologic process | + | ? |
| Sensitive and specific | + | − |
PYD: pyridinium crosslinks pyridinoline.