Comparison of clinical cut-points and treatment targets for urine NTX and plasma bCTX-I in XXXX .

@entity1 @entity8818 @entity1472 @entity174 @entity170 @entity4261 @entity2331 @entity562 @entity460 @entity1473
OBJECTIVE: We undertook to identify levels for plasma b isomerised @entity1473 -terminal telopeptides of type I collagen (p-bCTX-I) that are comparable to currently used urine @entity1472 -terminal telopeptides of type I collagen (u-NTX) cut-points and treatment targets in @entity170 . DESIGN AND METHODS: Fasting morning samples were collected from @entity1 attending tertiary hospitals and clinics for investigation of @entity2331 . @entity1 with @entity4261 or <20years of age were excluded. Second void spot urine for NTX and plasma (EDTA) samples were utilised. Urine was analysed routinely and plasma stored at -20C until analysis by enzyme-linked immunosorbent assay (ELISA) (Immunodiagnostic Systems plc), E170 (Roche Diagnostics) and IDS-iSYS (Immunodiagnostic Systems plc) methods. The relationship of u-NTX with each p-bCTX-I method's results was assessed by Passing and Bablok regression, and p-bCTX-I levels equivalent to u-NTX cut-points and targets were interpolated. RESULTS: One hundred and forty six @entity1 were included. Spearman correlation coefficients ranged from 0.71 to 0.75 for the three bCTX-I assays. The equivalent bCTX-I concentrations for NTX/ @entity8818 values of 21 ( @entity174 risk reduction target following @entity562 therapy), 27 (healthy pre-menopausal @entity1 's mean value), and 38 (threshold for reduction of BMD on @entity460 alone) nmol BCE/mmol were 230, 312 and 462ng/L for the automated Roche assay and 271, 395 and 624ng/L for the automated IDS i-SYS assay respectively. CONCLUSIONS: The p-bCTX-I equivalent to the only available @entity174 outcome based absolute treatment threshold of 21nmol BCE/mmol established for u-NTX, is close to 250ng/L but will vary between p-bCTX-I assays.
