Urinary excretion of pyridinolines crosslinks measured by immunoassay and HPLC techniques in normal subjects and in elderly patients with vitamin D deficiency

Hydroxylysylpyridinoline (HP) and lysylpyridinoline (LP) are specific constituents of mature skeletal collagens excreted in urine. Their measurement represents a sensitive index of bone resorption. In this study, we have measured urinary excretion of pyridinolines crosslinks by immunoassay (ELISA) and HPLC methods in 80 patients with different bone resorption rates. We chose a sample of 44 healthy adults (30 men and 14 women) and a sample of 36 elderly patients (7 men and 29 women) presenting a secondary hyperparathyroidism due to a vitamin D deficiency. The correlation between HPLC ( x) and ELISA ( y) was judged satisfactory ( y=0.794 x+6.947, r=0.92). The sensitivity of pyridinolines estimation was 50 nmol/1 for immunoassay and 20 nmol/l for HPLC. The intra-assay and inter-assay coefficients of variation for the two analytical methods was